This position paper is devoted to learning and teaching technologies aimed at alleviating problems and addressing challenges faced by learners or teachers in mass classes. It reports on practical experiments run over the last terms at the Institute for Informatics of Ludwig-Maximilian University of Munich, Germany. Furthermore, perspectives for higher education opened by technology are discussed: Digital social learning and/or experimentation spaces and technology-based personalization. It is further argued that such approaches provide specific advantages that are not only desirable for teaching mass classes.

    @conference{csedu22,
         author={Sven Strickroth. and Fran\c{c}ois Bry.},
         title={The Future of Higher Education Is Social and Personalized! Experience Report and Perspectives},
         booktitle={Proceedings of the 14th International Conference on Computer Supported Education - Volume 1: CSEDU,},
         year={2022},
         pages={389-396},
         publisher={SciTePress},
         organization={INSTICC},
         doi={10.5220/0011087700003182},
         isbn={978-989-758-562-3},
    }
    

@article{PMS-FB-2021-5,
title={An Asymptotic Analysis of Probabilistic Logic Programming, with Implications for Expressing Projective Families of Distributions},
volume={21},
DOI={10.1017/S1471068421000314},
number={6},
journal={Theory and Practice of Logic Programming},
publisher={Cambridge University Press},
author={Felix Weitkämper},
year={2021},
pages={802–817}
  }

@inbook{PMS-FB-2021-4,
  author = {Felix Weitkämper and Beatrice Sarbu and Kailin Sun},
  editor = { Joaquin Arias and Fabio Aurelio D’Asaro and Abeer Dyoub and Gopal Gupta and Markus Hecher and Emily LeBlanc and Rafael Peñaloza and Elmer Salazar and Ari Saptawijaya and Felix Weitkämper and Jessica Zangari},
  title = {Modelling infectious disease dynamics with probabilistic logic programming},
  booktitle = {ICLP 2021 Workshop Proceedings},
  publisher = {CEUR-WS},
  year = {2021}
  }

@inbook{PMS-FB-2021-3,
  author = {Kilian Rückschloß and Felix Weitkämper},
  editor = { Joaquin Arias and Fabio Aurelio D’Asaro and Abeer Dyoub and Gopal Gupta and Markus Hecher and Emily LeBlanc and Rafael Peñaloza and Elmer Salazar and Ari Saptawijaya and Felix Weitkämper and Jessica Zangari},
  title = {Reasoning about Independence in Open Universe Probabilistic Logic Programs},
  booktitle = {ICLP 2021 Workshop Proceedings},
  publisher = {CEUR-WS},
  year = {2021}
  }

This article reports on a scheme to exploit human computation and data science for fostering financial markets’ efficiency. The scheme consists in incentivizing market’s agents to assess their own risk of defaulting to financial contracts (that is, human computation) and in an eigenvector model of credit risk (that is, data science) aggregating agents’ assessments of their defaulting risk estimates into a global, or systemic, credit risk rating. The systemic credit risk rating in turn informs the market’s agents what nudges them to decisions beneficial not only to themselves, but also to the market as a whole.

    @inbook{PMS-FB-2021-2,
      author = {François Bry},
      title = {Informing a Financial Market},
      booktitle = {Decision Economics: Minds, Machines, and their Society.
    Proceedings of the 2nd International Conference on Decision Economics (DECON 2020)}
      pages = {238–247},
      publisher = {Springer-Verlag},
      year = {2021}
    }
    

@inbook{PMS-FB-2021-1,
  author = {Felix Weitkämper},
  editor = {Ralf Drechsler and Daniel Große},
  title = {Axiomatizing Boolean Differentiation},
  booktitle = {Recent Findings in Boolean Techniques}
  chapter = {4},
  pages = {83-104},
  publisher = {Springer-Verlag},
  year = {2021},
  url = {https://www.springer.com/gp/book/9783030680701}
  }

Coinduction refers to both a technique for the definition of infinite streams, so-called codata, and a technique for proving the equality of coinductively specified codata. This article first reviews coinduction in declarative programming. Second, it reviews and slightly extends the formalism commonly used for specifying codata. Third, it generalizes the coinduction proof principle, which has been originally specified for the equality predicate only, to other predicates. This generalization makes the coinduction proof principle more intuitive and stresses its closeness with structural induction. The article finally suggests in its conclusion extensions of functional and logic programming with limited and decidable forms of the generalized coinduction proof principle.

    @misc{bry2020coinduction,
          title={Coinduction Plain and Simple},
          author={François Bry},
          year={2020},
          eprint={2007.09909},
          archivePrefix={arXiv},
          primaryClass={cs.PL}
    }

Aus Sicht der Informatik und einer technik- und internetaffinen Kunstwissenschaft vertritt der vorliegende Beitrag die Auffassung, dass die digitale Kunstgeschichte in Zukunft noch stärker als bisher vom Umgang mit virtuellen 3D-Welten, vom Aufbau neuer Datensammlungen, von neuen Formen der Zusammenarbeit unter Wissenschaftlern und von der Bürgerwissenschaft geprägt werden dürfte.

@inbook{PMS-FB-2020-6,
        author = {François Bry and Bernd Krysmanski},
        title = {Von analogen und digitalen Zugängen zur Kunst – Festschrift für Hubertus Kohle zum 60. Geburtstag},
        editor={Maria Effinger and Stephan Hoppe and Harald Klinke and Bernd Krysmanski}
        chapter = {Vier Gedanken zur digitalen Kunstgeschichte},
        pages = {433-443},
        publisher = {Heidelberg: arthistoricum.net 2019},
        type = {{unknown}},
        year = {2010},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2020-6}
}

A distributed logic programming language with support for meta-programming and stream processing offers a variety of interesting research problems, such as: How can a versatile and stable data structure for the indexing of a large number of expressions be implemented with simple low-level data structures? Can low-level programming help to reduce the number of occur checks in Robinson's unification algorithm? This article gives the answers.

@INPROCEEDINGS{prokosch2020lowlevelindex,
  author =       {Thomas Prokosch},
  title =        {Give Reasoning a Trie},
  year =         2020,
  booktitle =    {Proceedings 36th International Conference on Logic
                  Programming (ICLP'20)},
  series =       {Electronic Proceedings in Theoretical Computer Science},
  month =        sep,
  volume =       325,
  publisher =    {Open Publishing Association},
  pages =        {303--312},
  doi =          {https://doi.org/10.4204/EPTCS.325.40},
  url =          {https://eptcs.org/paper.cgi?ICLP2020.40},
}
            

Technology Enhanced Learning (TEL) can be used to improve the learning experience of aspiring programmers. Additionally, gamification elements can be used to increase students’ motivation. This research paper focuses on a tool utilizing both TEL and gamification ele- ments: A coding platform that provides challenges for users to solve in order to improve their programming skills. Well-known coding platforms include Codewars and CodinGame, the us- age of which had a positive effect on undergraduate students’ motivation [1]. Inspired by the aforementioned approaches, this research paper describes a coding platform with more focus on competition and its evaluation in the context of tertiary programming education. On most coding platforms, users solve coding challenges in a playful manner, but have no way to interact with each other while solving a programming challenge. Adding the ability to play against another user in real-time could further enhance a user’s learning experience and motivation. In this research paper, we seek to answer the question whether this notion of competition can increase motivation to solve programming tasks.
We implemented the coding platform SuperDevBros to investigate this question. The main purpose of this platform is to provide one-on-one programming challenges for two users to compete against each other in real-time.
Two user studies were conducted in order to evaluate the effects of real-time competition on users’ self-assessment, enjoyment, and motivation. In addition to subjective feedback from questionnaires, the participants’ objective performance while using the platform was recorded. After the user studies were completed, data was gathered and evaluated from the users’ interactions with the system and their subjective feedback. Some of this data was collected at multiple phases of the study to observe changes in the participants’ attitudes triggered by the competitive mode.
Of particular interest was the comparison of the participants’ objective performance and their perceptions, i.e. regarding their self-assessment, enjoyment and motivation. The results of this study suggest that this kind of competitive environment in programming leads to learners assessing themselves more distinctively, while their enjoyment decreases. Fur- thermore, learners’ motivation drops in competition with others, but remains on a high level. Learners who already achieved a relatively high level of programming knowledge are generally more inclined to enjoy competitive gamification components in programming. Despite of the limited generalizability of the results, we conclude that competition in pro- gramming education does not necessarily have solely positive effects on learners’ experiences. The inclusion of competition in tertiary computer science education might prove to be use- ful, but further research needs to be conducted to identify the best way of integrating it into educational concepts.

@inproceedings{kofi2020effects},
  author    = {Konrad Fischer and Sarah Vaupel and Niels Heller and Sebastian Mader and Francois Bry},
  title     = {Effects of Competitive Coding Games on Novice Programmers},
  booktitle = {Educating Engineers for Future Industrial Revolutions - Proceedings of the 23rd International Conference on Interactive Collaborative Learning (ICL2020).},
  volume    = {2},
  publisher = {Springer},
  year      = {23-25 September 2020},
  pages     = {to appear}
}         

This article proposes a Technology-Enhanced Learning application which exploits both Human Computation and Learning Analytics to improve the learning and teaching of Science, Technology, Engineering and Mathematics (STEM) while reducing the teachers' workload. Specifically, the application aims at tracking and reducing learners' misconceptions and easing teachers' corrections of homework. To achieve this goal, the proposed software uses text-processing, collaborative filtering, and teacher collaboration in a wiki-like environment. While the software has not been implemented as a whole, its main components have been implemented and evaluated in several case studies. These studies point to the realisability and effectiveness of the approach.

@inbook{inbook,
  author       = {Niels Heller and Francois Bry},
  title        = {Human Computation for Learning and Teaching or Collaborative Tracking of Learners' Misconceptions},
  chapter      = to appear,
  pages        = {to appear},
  publisher    = {Elsevier},
  year         = 2020,
  volume       = 4,
  series       = ColMooc,
}            

A data structure providing an efficient storage and retrieval of logical expressions is a necessary component of every automated reasoning system. Most theorem provers rely on term indexes tuned to unification. Tabled logic programming systems in contrast favour indexes tuned to the retrieval of variants or instances. This article proposes the versatile data structure Instance Trie which supports the unification of queries with stored expressions as well as the retrieval of variants, instances, and generalisations of queries. Instance tries are stable in the sense that their structure is independent of the order in which they are filled or updated. They give rise to an incremental expression retrieval.

@INPROCEEDINGS{prokosch2020reasoningtrie,
  author =       {Thomas Prokosch and Fran{\c{c}}ois Bry},
  title =        {Give Reasoning a Trie},
  year =         2020,
  editor =       {Pascal Fontaine and Konstantin Korovin and Ilias S.
                  Kotsireas and Philipp R{\"{u}}mmer and Sophie
                  Tourret},
  booktitle =    {Joint Proceedings of the 7th Workshop on Practical
                  Aspects of Automated Reasoning {(PAAR)} and the 5th
                  Satisfiability Checking and Symbolic Computation
                  Workshop (SC-Square) Workshop},
  series =       {CEUR Workshop Proceedings},
  address =      {Aachen},
  volume =       2752,
  pages =        {93--108},
  publisher =    {CEUR-WS.org},
  url =          {http://ceur-ws.org/Vol-2752/paper7.pdf},
  note =         {urn:nbn:de:0074-2752-0}
}
            

This article describes a unification algorithm based on Robinson's unification algorithm using low-level system programming techniques. This change of perspective unlocks optimizations hardly recognizable in the widely used abstract mathematical formulation of unification algorithms: Unnecessary occurs-checks are recognized and avoided.

@INPROCEEDINGS{prokosch2020unifrun,
  author =       {Thomas Prokosch and François Bry},
  title =        {Unification on the Run},
  booktitle =    {The 34th International Workshop on Unification (UNIF'20)},
  year =         2020,
  editor =       {Temur Kutsia and Andrew M. Marshall},
  number =       {20-10},
  series =       {RISC Report Series},
  pages =        {13:1-13:5},
  month =        jun,
  url =          {https://www.risc.jku.at/publications/download/risc_6129/proceedings-UNIF2020.pdf},
  address =      {Linz, Austria},
  timestamp =    {2020-06-25},
  publisher =    {Research Institute for Symbolic Computation,
                  Johannes Kepler University}
}
            

This article reports on a novel higher-education course format exploiting choreographed peer reviews and self-corrections using an online learning platform. The novel course format aims to reduce teachers' workload as it was motivated by the necessity to run examinations for all courses during all terms, even though almost all courses can only be offered every second term. As a consequence, and because of a very high students-to-teacher ratio, many students have to prepare for examinations without sufficient assistance. This article describes the novel course format and reports on its evaluation in a case study. The evaluation indicates that most students benefit from the novel course format but that it is less efficient than traditional formats based on a higher teachers' involvement. The major weakness of the novel format is the insufficient participation of some students to their peer-reviewing. The article suggests and discusses possible measures to address that weakness. This article extends previous work by the same authors by providing an extended evaluation of the students' attitudes towards the course format, their behavior on the platform and their peer reviews. The course format and the learning platform are described in greater detail and the integration into related work has been expanded.

  @article{heller2019organizing,
  title={Organizing Peer Correction in Tertiary STEM Education: An Approach and its Evaluation},
  author={Heller, Niels and Bry, Francois},
  journal={International Journal of Engineering Pedagogy (iJEP)},
  volume={9},
  number={4},
  pages={16--32},
  year={2019}
}

Beginners are often unaccustomed to the abstract and formal thinking required in tertiary computer science education. This can be alleviated through close support provided by an experienced person, like a teacher. Nowadays, such support is hardly possible because, in computer science, instructors face classes of a few ten to a few hundred students. This article shows how scaffolding and feedback needed by computer science beginners can be provided by software. The particularly difficult case of building logical proofs is considered so as to demonstrate the effectiveness of the approach. The approach to computer‐provided scaffolding and feedback presented in this article is based on specifically designed proof editors that relieve learners from some choices and tasks – scaffolding – and provide immediate feedback on those tasks left to the learners. Building logical proofs is especially challenging – not only for beginners – because it includes various challenges: Understanding definitions, building a syntactically correct proof, and correctly applying complex proof building rules. This article introduces two specialized editors that support students in learning the proof methods Resolution and Natural Deduction. The editors make it possible for learners to focus on the correct order of rule application – the most challenging part of proof building –, by relieving them of the other aspects of proof building, and providing immediate feedback on the correctness of proof construction tasks performed by the learners. The contributions of this article are twofold: First, the conception and implementation of two original graphical proof editors, and second, a report on an evaluation of the editors and the feedback and scaffolding they provide pointing to the educational approach’s effectiveness.

  @inproceedings{staudacher2019proof,
    title={Automated Scaffolding and Feedback for Proof Construction: A Case Study},
    author={Staudacher, Korbinian and Mader, Sebastian and Bry, Fran{\c{c}}ois},
    booktitle={Proceedings of the 18th European Conference on e-Learning (ECEL 2019)},
    pages={542--550},
    year={2019},
    publisher={ACPI}
  }

Adding narrative, that is, a story, to gamification and educational games can boost students’ motivation and engagement. This requires a narrative fitting the course in which it will be deployed to and a gameplay to which the narrative fits without seeming to be tacked on. In this article, a gamification template called Reification and an education game template called Synapses are introduced both aiming at relieving educators from having to find an appropriate game or gamification leaving them only the task of finding a fitting narrative. Reification is making something abstract concrete with the intention of making the represented concept more tangible. In case of the gamification mechanism Reification, a learner’s progress in a course is made concrete through visualization: A student’s progress is visualized as a landscape in which each object, such as a tree, makes concrete one of the student’s accomplishments, such as a solved exercise. Reification aims to provide students with a tangible overview of their learning progress and allows them to compare their landscape to their peers’. Reification is illustrated in the article with a course on Egyptology. Synapses is a game which supports students in overcoming and preventing the development of misconceptions, which are commonly held incorrect beliefs by students about courses’ contents. After each lecture, students are tasked to organize parts of the lecture’s content in a concept map, or to revise their concept maps in reaction to mistakes made in exercises. The game’s narrative takes different turns depending on the percentage of students having a correct concept map. Synapses is illustrated in the article with a course on Logic. This article represents a work ­in­ progress: The concepts are grounded in theory with evaluations of the introduced implementations planned for future work.

@inproceedings{mader2019narrative,
  title={Adding Narrative to Gamification and Educational Games With Generic Templates},
  author={Mader, Sebastian and Heller, Niels and Bry, Fran{\c{c}}ois},
  booktitle={Proceedings of the 18th European Conference on e-Learning (ECEL 2019)},
  pages={360-368},
  year={2019},
  publisher={ACPI}
}

Audience response systems (ARS) allow lecturers to run quizzes in large classes by handing to technology the time-consuming tasks of collecting and aggregating students' answers. ARSs provide immediate feedback to lecturers and students alike. The first commercial ARSs emerged in the 1990s in form of clickers, i.e., transmitters equipped with a number of buttons, which impose restrictions on possible questions – most often, only multiple choice and numerical answers are possible. Starting from the early 2010s, the ubiquity of smartphones, laptops, and tablet computers paved the way for web-based ARSs which, while running on technology that provides more means for input and a graphical display, still have much in common with their precursors: Even though more types of questions besides multiple choice are supported, the full capability of web-based technology is still not fully exploited. Furthermore, they also do not adapt to a student's needs and knowledge, and often restrict quizzes to two phases: Answering a question and viewing the results. This article first examines the current state of web-based ARSs: Question types found in current ARSs are identified and their support in a variety of ARSs is examined. Afterwards, three axes on which ARSs should advance in the future are introduced: Means of input, adaption to students, and support for multiple phases. Each axis is illustrated with concrete examples of quizzes.

  @inproceedings{mader2019audienceresponsesyystem,
    title={Audience Response Systems Reimagined},
    author={Mader, Sebastian and Bry, Fran{\c{c}}ois},
    booktitle={Advances in Web-Based Learning – ICWL 2019},
    pages={to appear},
    year={2019},
    publisher={Springer}
  }

This article reports on patterns of behaviour among students learning several of the formal languages taught in STEM using a multi-language text editor that detects syntactic errors. Conveying formal languages such as programming languages and mathematical formalisms is an essential and difficult, yet little investigated, aspect of STEM education. An intensive evaluation based on the use of the editors in teaching seven different programming languages in two university courses in computer science has first manifested a significant correlation between the editors’ use and examination success. The evaluation has also unveiled interesting patterns of behaviour in the editors’ use among students succeeding at the examination: They not only extensively used the editors but also used them in a manner which can be called “code fiddling”, that is, experimenting with code examples from the learning material by modifying it, while using the editors over longer periods of time than non-fiddling students. The evaluation has also shown that the students consider the editors useful for their learning. This article reports on the afore-mentioned educational approach to teaching STEM formal languages and on its evaluation. It furthermore indicates implications for future research and for STEM teaching.

@inproceedings{heller2019learning,
  title={Learning by Fiddling: Patterns of Behaviour in Formal Language Learning},
  author={Heller, Niels and Bry, Fran{\c{c}}ois},
  booktitle={International Conference in Methodologies and intelligent Systems for Techhnology Enhanced Learning},
  pages={28--36},
  year={2019},
  organization={Springer}
}

Peers providing feedback on their peers’ work is called peer review which has been shown to have beneficial effects on students’ learning. This article presents a novel approach to peer review where reviewers, reviewees, and lecturers alike have access to the same documents, and reviews are created in form of annotations which are automatically shared among all users, can be up- or downvoted, and can themselves be commented on. Working on a same document and seeing annotations immediately after they have been created enables various forms of collaboration among learners: Between reviewers who can agree or disagree with a review by up- or downvoting or comment on the review thus providing further insight, between reviewers and reviewees by allowing the reviewees to inquire about reviews and reviewers to provide clarifications and justifications, and between lecturers and reviewers, when lecturers take the role of reviewers and up- or downvote and comment on reviews. The contributions of this article are twofold: First, a report on the conception and implementation of a collaborative annotation environment that supports the collaborative peer review described in this article, and second, an analysis of the communication that happened during collaborative peer review in three courses pointing to the approach’s effectiveness but uncovering problems of the collaborative annotation system as well.

@inproceedings{mader2019towards,
  title={Towards an Annotation System for Collaborative Peer Review},
  author={Mader, Sebastian and Bry, Fran{\c{c}}ois},
  booktitle={International Conference in Methodologies and intelligent Systems for Techhnology Enhanced Learning},
  pages={1--10},
  year={2019},
  organization={Springer}
}

Social media hold great promises in tertiary mass education because they foster the creation and sharing of information among communities. With educational social media, students can exchange on courses' contents and discuss homework solutions while being supervised by teachers. However, all too often social media are used in education as mere organisational tools, delivery tools for course material, or collection tools for homework assignments. This article reports on a versatile social medium which, among others, exploits collaborative correction, a form of human computation, for tracking systematic errors of STEM students. Learning analytics generated from both human-produced and systemcollected data and the results of a real-life evaluation are presented. The results point to a positive reception by students and teachers alike and to the effectiveness of the medium for higher STEM education.

@inproceedings{heller2019collaborativecorrection,
  title={Collaborative Correction in Mass Education as a Social Media Application},
  author={Heller, Niels and Bry, Fran{\c{c}}ois},
  booktitle={Proceedings of the 6th European Conference on Social Media (ECSM 2019)},
  pages={to appear},
  year={2019},
  organization={ACPI}
}

This article reports on coupled smartwatch and smartphone pervasive apps enabling stress self-regulation. Stress, the physiological responses of an organism to demanding conditions, can be both beneficial and harmful. Beneficial stress, or eustress, enhances physical or mental abilities. Harmful stress, or distress, can result in reduced abilities, anxiety, or depression. The potential of pervasive computing to enable stress self-regulation, that is, the ability to benefit from eustress while avoiding or limiting distress, is explored in this article. It first reports on Stila Computed Stress, a stress estimate computed after an original model from pulse rates delivered by smartwatches. This article then describes how Stila Computed Stress is combined with users' activity reports and pervasively delivered on their smartwatches and smartphones. It further reports on a real life evaluation pointing to the pervasive apps' persuasiveness, that is, the apps' capacity to increase subjective stress awareness so as to enhance stress self-regulation.

@InProceedings{PMS-FB-2019-4,
  author        = {Yingding Wang and Nikolai Fischer and Fran\c{c}ois Bry},
  title         = {Pervasive Persuasion for Stress Self-Regulation},
  booktitle     = {2019 IEEE International Conference on Pervasive Computing and Communications Workshops (PerCom Workshops)},
  year          = {2019},
  pages         = {724--730},
}

The traditional lecture is a teaching format which offers students few opportunities for engagement turning them into passive listeners of the lecturers’ presentations what negatively impacts on their learning. With audience response systems, that is technology supporting classroom quizzes, breaks which reactivate the students can be introduced into the lecturers’ presentations. This article reports on an audience response system coupled with a social gamification of quizzes based on teams: Each student is assigned to a team and the students’ answers to quizzes contribute to their team’s success. An immediate overview of team participation updated in real-time during the quiz and updated team standings after the quiz displayed for everyone to see motivate students to participate in the quizzes. The contribution of this article is threefold: First, a team-based social gamification of quizzes aimed at boosting participation in quizzes and attendance at lectures, second, original technological tools supporting the proposed team-based social gamification, and third, a first evaluation demonstrating its effectiveness in a small course and a second evaluation suggesting that for use in large classes teams have to be built in a specific way. This article is an extended version of an article presented at ICL 2018 which provides a deeper representation of related work, a more extensive description of the team component, an additional evaluation, and implications for the use of the team-based social gamification in large classes.

@article{mader2019fun,
  title={Fun and Engagement in Lecture Halls through Social Gamification},
  author={Mader, Sebastian and Bry, Fran{ç}ois},
  journal={International Journal of Engineering Pedagogy},
  pages={117--136},
  volume={15},
  number={2},
  year={2019},
  publisher={International Association of Online Engineering}
}

Nudging students to a better learning is a common practice among teachers of small classes which is impossible in large classes. Indeed, no teacher has enough time for giving individual feedback to several tens or hundred students, let alone be sufficiently aware of the progress and difficulties of each of them. This article reports on a case study using computed individual predictions for sustaining the motivation of large class’ audiences thus nudging them to a better learning. More precisely, this article reports on a case study in which students are given individual predictions of their withdrawal, or “skipping”, and examination performances with the aim of increasing their participation to classes and to homework. A real-life evaluation of the approach in a computer sicence course points to both its effectiveness and its positive reception by students.

@inproceedings{heller2019nudging,
  author={Heller, Niels and Bry, Fran{ç}ois},
  title={Nudging by Predicting: A Case Study},
  booktitle={Proceedings of the 11th International Conference on Computer Supported Education - Volume 2: CSEDU},
  year={2019},
  pages={236--243},
  publisher={SciTePress},
}

Limited interaction and passivity among students are inherent to the traditional lecture teaching format when deployed in large classes. With Backstage, these challenges were tackled by introducing a backchannel coupled with an audience response system into large-class lectures. A backchannel enables students to post questions and answer to questions without the fear of speaking out; an audience response system supports quizzes that help keeping the students' attention. The first version of Backstage focussed exclusively on lectures; an updated version supports a variety of learning and teaching formats that can be conceived by composing core components. Backstage provides a set of generic components that can be combined in order to create different formats ranging from completely asynchronous, to blended learning, to completely synchronous. Additionally, Backstage provides gamification features that go beyond run-of-the-mill solutions as points, badges, and leaderboards and learning analytics. In the demonstration, the main components of Backstage, the collaborative annotation tool, the vertical stream, the audience response system, the gamification, and the learning analytics are introduced and their use demonstrated by means of a variety of learning and teaching formats implemented using the components.

@conference{mader2019phasedclassroom,
  author={Mader, Sebastian and Bry, Fran{ç}ois},
  title={Phased Classroom Instruction: A Case Study on Teaching Programming Languages},
  booktitle={Proceedings of the 11th International Conference on Computer Supported Education - Volume 1: CSEDU},
  year={2019},
  pages={241--251},
  publisher={SciTePress},
}

@inproceedings{deSousaBorges:2014:SMG:2554850.2554956,
  author={Heller, Niels and Mader, Sebastian and Bry, Fran{ç}ois},
  title={More than the Sum of its Parts: Designing Learning Formats from Core Components},
  booktitle = {Proceedings of the 34th ACM/SIGAPP Symposium On Applied Computing},
  year = {2019},
  location = {Limassol, Cyprus},
  pages = {to appear},
  publisher = {ACM},
}

Source code search is frequently needed and important in software development. Keyword search for source code is a widely used but a limited approach. This paper presents CodeKōan, a scalable engine for searching millions of online code examples written by the worldwide programmers' community which uses data parallel processing to achieve horizontal scalability. The search engine relies on a token-based, programming language independent algorithm and, as a proof-of-concept, indexes all code examples from Stack Overflow for two programming languages: Java and Python. This paper demonstrates the benefits of extracting crowd knowledge from Stack Overflow by analyzing well-known open source repositories such as OpenNLP and Elasticsearch: Up to one third of the source code in the examined repositories reuses code patterns from Stack Overflow. It also shows that the proposed approach recognizes similar source code and is resilient to modifications such as insertion, deletion and swapping of statements. Furthermore, evidence is given that the proposed approach returns very few false positives among the search results.

@inproceedings{PMS-FB-2018-9,
 author = {Schramm, Christof and Wang, Yingding and Bry, Fran\c{c}ois},
 title = {Codek\={O}an: A Source Code Pattern Search Engine Extracting Crowd Knowledge},
 booktitle = {Proceedings of the 5th International Workshop on Crowd Sourcing in Software Engineering},
 series = {CSI-SE '18},
 year = {2018},
 isbn = {978-1-4503-5733-3},
 location = {Gothenburg, Sweden},
 pages = {1--8},
 numpages = {8},
 url = {http://doi.acm.org/10.1145/3195863.3195864},
 doi = {10.1145/3195863.3195864},
 acmid = {3195864},
 publisher = {ACM},
 address = {New York, NY, USA},
 keywords = {code patterns, mining crowd knowledge, search algorithm, source code search, source code similarity, stack overflow},
}

ARTigo (http://www.artigo.org/) ist sowohl eine Spieleplattform als auch eine semantische Suchmaschine für Kunstwerke. Die Spieler annotieren während des Spielens Kunstwerke; die gesammelten Annotationen werden dazu genutzt, um einen Index für Suchmaschinen aufzubauen, welcher durch die ständig neu hinzukommenden Annotationen fortlaufend vergrößert wird. Seit 2008 haben die täglich circa 150 Spieler auf der ARTigo-Plattform mehr als neun Millionen Annotationen für die Beschreibungen von Kunstwerken generiert. Die ARTigo-Spieleplattform kann als ein Ökosystem betrachtet werden, bei dem mithilfe verschiedener Arten von Spielen Annotationen unterschiedlicher semantischer Tiefe gesammelt werden. Description Games (Beschreibungsspiele) sammeln sehr allgemeine, auf augenfälligen Bildelementen beruhende Annotationen, Diversification Games (Mannigfaltigkeitsspiele) sammeln Annotationen mit einer größeren semantischen Tiefe, Integration Games (Verflechtungsspiele) sammeln genauere Informationen zu anderen Annotationen. Dieser Artikel stellt eine qualitative Analyse der von der ARTigo-Plattform gesammelten Annotationen vor. Er fokussiert sowohl auf die Leistungsfähigkeit des Ökosystems als Ganzes als auch auf die Leistungsfähigkeit der einzelnen Spiele, Annotationen unterschiedlicher semantischer Tiefen zu sammeln. Abschließend wird die ARTigo-Suche vorgestellt, mit der neben der inhaltlichen Suche nach Kunstwerken auch die Suchergebnisse analysiert werden können. Dadurch bekommt der Benutzer einerseits eine bessere Übersicht über die Suchergebnisse, anderseits können auch einfache datenanalytische Aufgaben gelöst werden.

@inbook{PMS-FB-2018-8,
	Address = {Heidelberg},
	Author = {François Bry and Clemens Schefels and Corina Schemainda},
	Date-Added = {2018-12-13 15:05:52 +0100},
	Date-Modified = {2018-12-13 15:08:23 +0100},
	Editor = {Piotr Kuroczyński and Peter Bell and Lisa Dieckmann},
	Publisher = {arthistoricum.net},
	Title = {Eine qualitative Analyse der ARTigo-Annotationen},
	Url = {\url{http://books.ub.uni-heidelberg.de/arthistoricum/catalog/book/413}},
	Year = {2018}}

Limited interaction and passivity among students are inherent to the traditional lecture teaching format when deployed in large classes. With Backstage, these challenges were tackled by introducing a backchannel coupled with an audience response system into large-class lectures. A backchannel enables students to post questions and answer to questions without the fear of speaking out; an audience response system supports quizzes that help keeping the students' attention. The first version of Backstage focussed exclusively on lectures; an updated version supports a variety of learning and teaching formats that can be conceived by composing core components. Backstage provides a set of generic components that can be combined in order to create different formats ranging from completely asynchronous, to blended learning, to completely synchronous. Additionally, Backstage provides gamification features that go beyond run-of-the-mill solutions as points, badges, and leaderboards and learning analytics. In the demonstration, the main components of Backstage, the collaborative annotation tool, the vertical stream, the audience response system, the gamification, and the learning analytics are introduced and their use demonstrated by means of a variety of learning and teaching formats implemented using the components.

@inproceedings{heller2018backstage,
  title={Backstage: A Versatile Platform Supporting Learning and Teaching Format Composition},
  author={Heller, Niels and Mader, Sebastian and Bry, Fran{ç}ois},
  booktitle={Proceedings of the 18th Koli Calling International Conference on Computing Education Research},
  year={2018},
  organization={ACM},
  doi={10.1145/3279720.3279747}
}

This article reports on a novel higher-education course format exploiting choreographed peer reviews and self corrections so as to reduce to a minimum the teachers' involvement. The novel course format was motivated by the necessity to run examinations for all courses during all terms, even though almost all courses are offered only every second term. As a consequence and because of a very high students to teacher ratio, many students have to prepare for examinations without sufficient assistance. This article describes the novel course format and reports on its evaluation in a case study. The evaluation indicates that most students benefit from the novel course format but that it is less efficient than traditional formats based on a much higher teachers' involvement. The major weakness of the novel format is an insufficient dedication of some students to their reviewing. The article suggests and discusses possible measures to address that weakness.

@inproceedings{mader2018gaming,
  author    = {Niels Heller and François Bry},
  title     = {Peer Teaching in Tertiary STEM Education: A Case Study},
  booktitle = {The Challenges of the Digital Transformation in Education - Proceedings of the 21st International Conference on Interactive Collaborative Learning (ICL2018)},
  volume    = {2},
  publisher = {Springer},
  year      = {25-28 September 2018},
  pages     = {to appear}
}

The traditional lecture is a teaching format that offers students few opportunities for interaction turning them into passive listeners of the lecturers’ presentations what negatively impacts on their learning. With audience response systems, that is technology supporting classroom quizzes, breaks that reactivate the students can be introduced into the lecturers’ presentations. This article reports on an audience response system coupled with a social gamification of quizzes based on teams: Each student is assigned to a team and the students’ answers to quizzes contribute to their teams’ success. An immediate overview of responses to quiz questions and the team standings motivates students to participate in the quizzes. The contribution of this article is threefold: First, a team-based social gamification of quizzes aimed at boosting participation in quizzes and attendance at lectures, second, original technological tools supporting the proposed team-based social gamification, and third, an evaluation of the approach demonstrating its effectiveness.The traditional lecture is a teaching format that offers students few opportunities for interaction turning them into passive listeners of the lecturers’ presentations what negatively impacts on their learning. With audience response systems, that is technology supporting classroom quizzes, breaks that reactivate the students can be introduced into the lecturers’ presentations. This article reports on an audience response system coupled with a social gamification of quizzes based on teams: Each student is assigned to a team and the students’ answers to quizzes contribute to their teams’ success. An immediate overview of responses to quiz questions and the team standings motivates students to participate in the quizzes. The contribution of this article is threefold: First, a team-based social gamification of quizzes aimed at boosting participation in quizzes and attendance at lectures, second, original technological tools supporting the proposed team-based social gamification, and third, an evaluation of the approach demonstrating its effectiveness.

@inproceedings{mader2018gaming,
  author    = {Sebastian Mader and François Bry},
  title     = {Gaming the Lecture Hall: Using Social Gamification to Enhance Student Motivation and Participation},
  booktitle = {The Challenges of the Digital Transformation in Education - Proceedings of the 21st International Conference on Interactive Collaborative Learning (ICL2018)},
  volume    = {2},
  publisher = {Springer},
  year      = {25-28 September 2018},
  pages     = {to appear}
}

One of the most vexing aspects of tertiary education is the learning behaviour of many beginners: Late drop-outs after much time has already been invested in attending a course, incomplete homework even though completed homework is a sufficient condition for success at examinations, and misconceptions that are not overcome early enough. This article presents three predictors related to these learning-impairing behaviours that have been built from data collected with a learning platform and by examining homework assignments, and developed as Hidden Markov Model, by relying on Collaborative Filtering, and by using Multiple Linear Regression. The sensitivities and specificities of the first two predictors are above 70% and the R²-error of the third predictor is about 20%. Considering the large numbers of unknown parameters like course-independent learning, this quality is satisfying. The predictors have been developed for fostering a better learning by raising the learners' consciousness of the deficiencies of their learning. In other words, the predictors aim at "getting it wrong". The article reports on the predictors and their evaluation.

  @inproceedings{PMS-FB-2018-4,
    author    = {Niels Heller and François Bry},
    title     = {Predicting Learners' Behaviours to Get it Wrong},
    booktitle = {Methodologies and Intelligent Systems for Technology Enhanced Learning, 8th International Conference},
    series    = {Advances in Intelligent Systems and Computing}
    publisher = {Springer}
    year      = {20-22 June 2018}
    pages     = {12-19}
  }

Seminars are difficult and therefore often neglected classes in STEM education even though they greatly contribute to the students' scientific maturity. Seminars are a traditional educational format blending classroom, collaborative, and individual learning: Seminar participants are tasked to discover, understand, and convey a scientific or technical issue to the other seminar attendees in an essay and in an oral presentation engaging them into a fruitful discussion. Seminars are rightly considered a cornerstone of STEM education, yet they are often frustrating experiences for both learners and teachers due to insufficient supervision and practice. This article reports on using Backstage 2, a web platform that, by offering a virtual space and tools for a fruitful communication, bridges classroom, collaborative, and individual learning activities. The contribution of this article is threefold: First, a class format aimed at boosting collaboration in seminars, second, technological tools supporting collaboration among seminar attendees, and third, an evaluation of the approach demonstrating its effectiveness.

@inproceedings{PMS-FB-2018-3,
  author    = {Sebastian Mader and François Bry},
  title     = {Blending Classroom, Collaborative, and Individual Learning using Backstage 2},
  booktitle = {Methodologies and Intelligent Systems for Technology Enhanced Learning, 8th International Conference},
  series    = {Advances in Intelligent Systems and Computing}
  publisher = {Springer}
  year      = {20-22 June 2018}
  pages     = {3-11}
}

Processing programs as data is one of the successes of functional and logic programming. Higher-order functions, as program-processing programs are called in functional programming, and meta-programs, as they are called in logic programming, are widespread declarative programming techniques. In logic programming, there is a gap between the meta-programming practice and its theory: The formalisations of meta-programming do not explicitly address its impredicativity and are not fully adequate. This article aims at overcoming this unsatisfactory situation by discussing the relevance of impredicativity to meta-programming, by revisiting former formalisations of meta-programming and by defining Reflective Predicate Logic, a conservative extension of first-order logic, which provides a simple formalisation of meta-programming.

@atechreport{bry2018praise,
    author  = {François Bry},
    title   = {In Praise of Impredicativity: A Contribution to the Formalisation of Meta-Programming},
    institution = {Institute for Informatics, Ludwig-Maximilian University of Munich, Germany},
    number  = {PMS-FB-2018-2},
    year    = {2018},
    url     = {https://pms.ifi.lmu.de/publications/PMS-FB/PMS-FB-2018-2/PMS-FB-2018-2-paper.pdf},
    note    = {Revised 26 November 2018}
 }
        

Until the middle of the 20th century, a reader would have stumbled against the phrase “Human Computation” because, at that time, computers were humans carrying out calculations, not machines. Back then, a special issue on “Machine Computation” would have aroused much interest. Nowadays, things are the other way around: A reader is likely to stumble against the phrase “Human Computation” because it is, nowadays, common knowledge that machines outperform human beings in a wide range of tasks; one might even wonder how humans could contribute to computations in a useful manner! Indeed, many human skills are far away from being fully taken over by machines. For example, reading comprehension, image recognition, or finding heuristic solutions for complex computational tasks like the traveling salesman problem still is beyond the capabilities of machines. Such tasks still are within humans’ reserved domain. It therefore seems natural that combining both the skills of humans and of machines can result in a higher problem solving competence both in quantity and quality. This insight paves the way for “Human Computation” as we know it today. This special issue introduces “Human Computation” through presentations of current research projects. The first article, "Mobile Learning in Environmental Citizen Science: An initial survey of current practice in Germany", reports on a survey of mobile learning among environmental citizen science projects. This first articles offers a good overview of why projects of very different types rely on “Citizen Science”, a form of “Human Computation”. The second article, "Design and Implementation of a Platform for the Citizen Science Project Migraine Radar", describes a Citizen Science platform based on a software architecture with different front-ends and a back-end. The scope of the project, Migraine Radar, is to establish a large data collection on migraine attacks so as to explore the triggering factors of such attacks. The third article, "Collective Organization of Discourse Expertise using Information Technology - CODE IT!", introduces a Citizen Science platform that helps to analyse and review press releases using the technique called “coding” in social sciences. The platform usage has been verified within a Citizen Science project where the participants reviewed articles on vaccination against the Human Papilloma Virus (HPV). The fourth article, "Not-So-Distant Reading: A Dynamic Network Approach to Literature", describes a novel approach to analysing the occurrence of characters in Victorian novels relying on a prototype system offering various visualizations. The article reports on a user study demonstrating the effectiveness of the approach. A fifth and final article, “Optimising Crowdsourcing Efficiency: Amplifying Human Computation with Validation”, is dedicated to investigating whether crowdsourcing, and therefore Human Computation, can be optimised with a validation process. The authors suggest a simple agreement validation step to enhance the quality of crowdsourcing’s outcomes. They prove the proposed technique with the Game With A Purpose (short GWAP) "Phrase Detectives" by measuring the quality, cost, noise, and speed of the collected validations. We hope that this special issue on Human Computation provides with a good, even though non-exhaustive, introduction to “Human Computation” and to its subfield “Citizen Science”. These fields are rapidly evolving and it is very likely that, in the forthcoming months and years, many novel applications of, and approaches to, “Human Computation” will be developed and tested. We therefore recommend the interested readers to keep an eye of forthcoming results and project reports!

@article{bry2018journalit,
    author  = {François Bry and Alexander Yong-Su Pohl},
    title   = {Editorial},
    journal = {Journal it - Information Technology (Special Issue on Human Computation)},
    volume  = {60},
    number  = {1},
    year    = {2018},
    pages   = {1-2},
    url     = {https://www.degruyter.com/view/j/itit.2018.60.issue-1/itit-2018-0007/itit-2018-0007.xml?format=INT}
 }
        

20th century iconic examples of human collaboration are the assembly line, centralised planning, bureaucracies, vote-based decision making, and school education. These examples, and more generally all forms of human collaboration of the 20th century, are characterized by predefined human roles and little adaptable processes, that is, 20th century collaboration comes at the price of a restricted individual freedom. With the turn of the century, new forms of human collaboration have become widespread that exploit information and communication technologies, data generated by humans, Data Science in general and Machine Learning in particular, and let humans contribute as they like, when they like, and as much as they can, the lack of predefined roles and processes being accounted for by software. The phrase "Human Computation" coined for denoting the new forms of human collaboration stresses a core aspect of the paradigm which can be a downside: With Human Computation, humans become contributors to collaboration-enabling algorithms that can also control and restrict how collaboration takes place. This article introduces to Human Computation and to its role in applications of Machine Learning, presents Human Computation prototype systems developed during the last decade at Ludwig-Maximilian University of Munich, discusses ethical issues of Human Computation and Machine Learning, points to on-going research in the field at Ludwig-Maximilian University of Munich, and concludes with a reflection on the future of Human Computation. The original contribution of this article is a comprehensive presentation of recent re-search the main part of which has already been published in more detail elsewhere.

@chapter{bogner2017humancollaboration,
    author    = {Martin Bogner and François Bry and Niels Heller and Stephan Leutenmayr and Sebastian Mader and Alexander Pohl and Yingding Wang and Christoph Wieser and Clemens Schefels},
    title     = {Human Collaboration Reshaped: Applications and Perspectives},
    editor    = {Arndt Bode and Manfred Broy and Hans-Joachim Bungartz and Florian Matthes},
    booktitle = {50 Jahre Universitäts-Informatik in München},
    publisher  = {Springer-Verlag},
    year    = {2017},
    pages   = {47-73},
    Chapter = {3}
    url     = {https://www.pms.ifi.lmu.de/publikationen/PMS-FB/PMS-FB-2017-2/PMS-FB-2017-2-paper.pdf}
 }
        

Purpose. Several challenges of today’s higher education were motivations to reconsider the contents and formats of lectures and tutorials and to conceive the classroom communication system Backstage, a social media platform supporting a novel form of large-class teaching. The purpose of this paper is to report on the challenges met, on the novel teaching form and on an evaluation of this teaching form.
Design/methodology/approach. The use of Backstage in two courses is evaluated. One of the courses has been specially adapted to promote student participation, the other course has been held in a traditional way. To investigate the usefulness and acceptance of Backstage in the given settings the data collected on Backstage and student responses in surveys are analyzed.
Findings. The results indicate that Backstage can foster interactivity and awareness in large-class lectures when used in combination with a teaching format that provides opportunities for and encourges lecture-relevant communication. Furthermore, students appreciated the use of Backstage.
Research limitations/implications. This paper reports on a case study which lacks generalizability. Further studies under controlled conditions and of the learning effectiveness of the approach are still outstanding.
Practical implications. This paper describes an approach fostering a form of Active Learning in large classes. Since large classes are widespread in higher education, the approach has a considerable practical potential.
Social implications. The paper describes an approach to large class higher education teaching in using social media.
Originality/value. Similar results have not been published so far.

@article{bry2018largeclass,
    author  = {François Bry and Alexander Yong-Su Pohl},
    title   = {Large class teaching with Backstage},
    journal = {Journal of Applied Research in Higher Education (Special Issue on reviewing the performance and impact of social media tools in higher education)},
    volume  = {9},
    number  = {1},
    year    = {2017},
    pages   = {105-128},
    doi     = {10.1108/JARHE-06-2015-0042},
    url     = {http://www.emeraldinsight.com/doi/full/10.1108/JARHE-06-2015-0042}
 }
        

ARTigo is both, a gaming platform and an artwork search engine: While playing, ARTigo's users leaves annotations describing artworks; these annotations are automatically processed by a higher-order latent semantic analysis for building, and continuously improving, an artwork search engine. ARTigo's search engine has been developed for, and with, art historians and covers more that 65,000 artworks of different styles and epochs. ARTigo is in operation since 2008.

ARTigo's gaming platform is an ecosystem consisting of different types of games aiming at collecting rich annotations of different type: Description games aim at collecting mere descriptions, diversification games aim at completing artwork descriptions with more specific characterizations, integration games cluster annotations so as to generate more precise descriptions. This article's analysis points to both, the effectiveness of ARTigo as a gaming ecosystem and the effectiveness of each of the games at collecting specific annotations.

@techreport{PMS-FB-2016-6,
        author = {François Bry and Clemens Schefels},
        title = {An Analysis of the ARTigo Gaming Ecosystem With a Purpose},
        institution = {Institute for Informatics, University of Munich},
        year = {2016},
        type = {Research Report},
        number = {PMS-FB-2016-6},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2016-6}
}
        

Die Universität München erprobt die Bürger/innenbeteiligung – erklärt mit Beispielen aus Forschung und Lehre.

@article{PMS-FB-2016-5,
    author    = {Clemens Schefels},
    title     = {Eine offene Universität für eine offene Gesellschaft},
    year      = {2016},
    journal   = {oead'news},
    publisher = {OeAD},
    volume    = {2016},
    month     = {October},
    number    = {101},
    language  = {German},
    url       = {https://issuu.com/oead.worldwide/docs/web_oead_news_101},
    pages     = {22--23}
}

Die Publikation "Citizen Science für alle“ ist eine praktische Ressource für Initiierende, Beteiligte und Interessierte an Citizen Science-Projekten. Die Handreichung liefert praktische Tipps für die Planung und Umsetzung von Citizen Science-Projekten und schafft einen Überblick zur Citizen Science-Praxis in Deutschland.

Welche Punkte muss ich bei der Projektplanung beachten? Wie kann ich Fördermittel einwerben? Welche Form der Öffentlichkeitsarbeit unterstützt mein Anliegen und motiviert Mitforscher? Im ersten Teil helfen viele praktische Tipps bei der Entwicklung des Projekts. Eine grafische Darstellung der Projektmeilensteine und eine Checkliste runden die Darstellung ab.

Im zweiten Teil wird die Umsetzung von Citizen Science in bestimmten Bereichen wie Naturschutz, Geisteswissenschaften oder im digitalen Raum beschrieben und reflektiert. Vierzehn verschiedene Projekte kommen hier über eingebaute "Geschichten" zu Wort und teilen ihre Erfahrungen mit den Lesenden.

Die Handreichung wurde von 31 Autorinnen und Autoren aus der Citizen Science-Community geschrieben und lektoriert. Koordiniert wurde die Publikation vom GEWISS-Projekt.

@misc{PMS-FB-2016-4,
    author    = {Lisa Pettibone and Katrin Vohland and Aletta Bonn and Anett Richter and Wilhelm Bauhus and Birgit Behrisch and Rainer Borcherding and Miriam Brandt and François Bry and Daniel Dörler and Ingrid Elbertse and Falko Glöckler and Claudia Göbel and Susanne Hecker and Florian Heigl and Michael Herdick and Sarah Kiefer and Thekla Kluttig and Elisabeth Kühn and Katarina Kühn and Silke Oldorff and Kristin Oswald and Oliver Röller and Clemens Schefels and Anne Schierenberg and Willi Scholz and Anke Schumann and Andrea Sieber and René Smolarski and Klaus Tochtermann and Wolfgang Wende and David Ziegler},
    title     = {Citizen Science für alle. Eine Handreichung für Citizen-Science Beteiligte},
    publisher = {GEWISS},
    month     = {Juni},
    year      = {2016},
    note      = {http://www.buergerschaffenwissen.de/sites/default/files/assets/dokumente/gewiss_citscifueralle_handreichung_web.pdf},
    url       = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2016-4}
}

Purpose: Several challenges of today’s higher education were motivations to reconsider the contents and formats of lectures and tutorials and to conceive the classroom communication system Backstage, a social media platform supporting a novel form of large-class teaching. This article reports on the challenges met, on the novel teaching form and on an evaluation of this teaching form.
Design/methodology/approach: The use of Backstage in two courses is evaluated. One of the courses has been specially adapted to promote student participation, the other course has been held in a traditional way. To investigate the usefulness and acceptance of Backstage in the given settings the data collected on Backstage and student responses in surveys are analyzed.
Findings: The results indicate that Backstage can foster interactivity and awareness in large-class lectures when used in combination with a teaching format that provides opportunities for and encourages lecture-relevant communication. Furthermore, students appreciated the use of Backstage.
Research limitations/implications: This article reports on a case study, which lacks generalizability. Further studies under controlled conditions and of the learning effectiveness of the approach are still outstanding.
Practical implications: This article describes an approach fostering a form of Active Learning in large classes. Since large classes are widespread in higher education, the approach has a considerable practical potential.

@article{PMS-FB-2016-3,
  author = {Alexander Pohl and François Bry},
  title = {Large-Class Teaching with Backstage},
  journal = {Journal of Applied Research in Higher Education},
  year = {2016}
}

Dieser Leitfaden verdeutlicht gängige Muster für mathematische Beweise anhand von Beispielen aus dem Alltag, der Mathematik und der Informatik. Er ist als studienbegleitende Lektüre für Studierende insbesondere in Informatik-Studiengängen gedacht.

Der vorliegende Teil II des Leitfadens behandelt hauptsächlich transfinite Ordinalzahlen und transfinite Induktion.

@techreport{PMS-FB-2016-2,
  author = {Hans J\"{u}rgen Ohlbach and Norbert Eisinger},
  title = {{Design Patterns f\"{u}r mathematische Beweise -- Ein Leitfaden insbesondere f\"{u}r Informatiker. Teil~\textrm{II}: Transfinite Ordinalzahlen und transfinite Induktion. Erste Auflage.

              }},
  institution = {Institute for Informatics, University of Munich},
  year = {2016},
  type = {{Skriptum/Lecture Notes}},
  number = {PMS-FB-2016-2},
  url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2016-2},
}

Dieser Leitfaden verdeutlicht gängige Muster für mathematische Beweise anhand von Beispielen aus dem Alltag, der Mathematik und der Informatik. Er ist als studienbegleitende Lektüre für Studierende insbesondere in Informatik-Studiengängen gedacht.

Der vorliegende Teil I des Leitfadens behandelt einfache und komplexere Beweismuster sowie Formen der vollständigen Induktion.

@techreport{PMS-FB-2016-1,
  author = {Hans J\"{u}rgen Ohlbach and Norbert Eisinger},
  title = {{Design Patterns f\"{u}r mathematische Beweise -- Ein Leitfaden insbesondere f\"{u}r Informatiker. Teil~\textrm{I}: Einfache und komplexe Beweismuster. Erste Auflage.

              }},
  institution = {Institute for Informatics, University of Munich},
  year = {2016},
  type = {{Skriptum/Lecture Notes}},
  number = {PMS-FB-2016-1},
  url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2016-1},
}

@article{PMS-FB-2015-4,
        author = {Alexander Pohl and François Bry},
        title = {Das Audience Response System Backstage},
        year = {2015},
        journal = "FNMA Magazin",
	volume = "2015",
	number = "4",
	language = {German},
        url = {http://fnm-austria.at/fileadmin/user_upload/documents/Magazin/2015-04.pdf},
	pages = "14--19"
}

This article reports on an analysis of the semantic quality of artwork annotations that have been collected by the web platform ARTigo from 2008 to 2014. ARTigo is both, a gaming platform for collecting semantic annotations and a semantic search engine: While playing games featuring artworks, one leaves data describing these artworks that are automatically used for building up, and continuously improving, an artwork search engine. ARTigo is an ecosystem consisting of different types of games aiming at collecting annotations of different semantic depth: Description games aim at collecting mere descriptions, diversification games aim at completing artwork descriptions with more specific characterizations, integration games cluster annotations so as to generate more precise descriptions. The qualitative analysis this article reports about points to both, the effectiveness of ARTigo as a gaming ecosystem and the effectiveness of each of game at collecting annotations with the desired semantic depth.

@techreport{PMS-FB-2015-1,
        author = {François Bry and Corina Schemainda and Clemens Schefels},
        title = {A Gaming Ecosystem Crowdsourcing Deep Semantic Annotations},
        institution = {Institute for Informatics, University of Munich},
        year = {2015},
        type = {Research Report},
        number = {PMS-FB-2015-1},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2015-1}
}

Mobile devices, such as laptops, smartphones and tablets, are ubiquitous in lectures. Students report to use their mobile devices for lecture-related activities (e.g. taking notes). Observational data shows, that students use mobile device mainly for lecture-unrelated activities, like Facebook or playing games. So currently, mobile devices seem to distract learners from the lecture and ultimately hinder student-teacher interaction. In this study, we investigated how students (N = 75) use their mobile devices (N = 80) in a traditional lecture setting when supported with the technological support system "Backstage" or not. Backstage entails functions for quizzing students (Audience-Response-System) and a backchannel allowing students to interact with each other, commenting on slides, asking questions, and providing feedback to lecturers. The results show that this technology increases students' focus on lecture-related activities.

@incollection{PMS-FB-2014-3,
        author = {Vera Gehlen-Baum, Armin Weinberger, Alexander Pohl, and François Bry},
        title = {Technology use in lectures to enhance student's attention},
        booktitle = {Procceedings of the 9th International Conference on Technology Enhanced Learning (EC-TEL)},
        address = {Graz, Austria},
        year = {16-19 September 2014}
}

@incollection{PMS-FB-2014-2,
        author = {François Bry and Alexander Pohl},
        title = {Backstage: A Social Medium for Large Classes},
        booktitle = {Campus Transformation -- Education, Qualification and Digitalization},
        editor = {Frank Keuper and Heinrich Arnold},
        publisher = {Logos Verlag},
        address = {Berlin},
        pages = {255--280},
        year = {2014},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2014-2}
}

Annotating is an important part when working with literature, especially in science. Up to now, a person’s annotations are private or only shared with a small group of other persons who are granted access to the notes or the annotated media. A proof of concept prototype called BibPad has been realized that allows users to create, share, and collaborate on annotations. These annotations contain information about the annotated media that go far beyond usual meta data and can be used to build a library search engine through crowdsourcing. Crowdsourcing a library search engine is in fact the reason why BibPad has been conceived and developed.
To reach this goal, this paper examines different classes of physical annotations and proposes appropriate digital representations. This takes into account that most of a library's media is not available digitally. For this reason, BibPad is built in a way that supports both the annotation of digital and the annotation of physical media. Moreover, the annotations are not bound to a specific media, e.g., if at some point a digital version is available, the annotations of the physical version can be reused.
BibPad is mainly intended for the use in libraries. Users can easily add media via a barcode scan to their personal library and start creating annotations. Now that the annotations are digitally available, new possibilities for social interaction are opened up: users can create groups to share media and associated annotations with or even create public annotations. A shared annotation can be flagged as editable; in this case, every group member can edit and contribute to the annotation.
This paper results from an ongoing joint research project with the Bayerische Staatsbibliothek and the University of Munich. The Bayerische Staatsbibliothek possesses a large inventory of WWI media. Goal of this research project is to develop a semantic search engine for these media.

@inproceedings{PMS-FB-2014-1,
        author = {Sebastian Mader and Christoph Wieser and François Bry and Clemens Schefels},
        title = {BibPad as a Library Service or Crowdsourcing a Library Search Engine.},
        booktitle = {Book of Abstracts of the 6th International Conference on Qualitative and Quantitative Methods in Libraries},
        year = {2014},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2014-1}
}

The market metaphor offers a promising form of human computation for gathering and aggregating individual opinions into a collective point of view for groups of people. In this article, we identify different kinds of market forms, their specific goals, and their participants' behavior. Building on this, we first identify appropriate reward designs for a good functioning of the markets as opinion aggregators. Furthermore, we stress potential possibilities for facilitating participants' learning. To illustrate and validate the approach proposed, we investigate two different market applications with different kinds of rewards and goals.

@inproceedings{PMS-FB-2013-12,
        author = {Stephan Leutenmayr and Fabian Kneissl and Sven Ziemer and François Bry},
        title = {{Gameful Markets for Collaboration and Learning}},
        year = {2013},
        booktitle = {In Proc. of Disco 2013, Workshop on Human Computation and Machine Learning in Games at HComp 2013},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-12}
}

The application of the market metaphor to forecasting uncertain future events exhibits appealing characteristics such as forecast accuracy and being considered attractive by most users. Based on the demonstrated success of such so called prediction markets as an accurate forecasting mechanism, the market metaphor has been applied to related domains such as decision making and decision support in order to benefit from its attractive characteristics. However, not all of those characteristics still hold in these application areas. We currently develop Liquid Decision Making (LDM), a market based approach for group decision making. This article reports on three design principles that we devised to address the aforementioned challenges, namely the principles of a collaborative decision making situation, a personal involvement of the participants with the decision at hand and dual incentives provided to the users. A prototypical implementation of this LDM mechanism has been tested for decision making in a scenario building seminar. There, participants gathered, categorized and ranked driving factors for their relevance for scenarios to be developed for the topic of personalized mobility in 2050. In this setting, the design principles of the mechanism were deemed to be viable for addressing the challenges of attracting and retaining participants.

@inproceedings{PMS-FB-2013-11,
        author = {Stephan Leutenmayr and Sven Ziemer and François Bry},
        title = {Decision Markets for Continuously Reflected Collective Decisions},
        year = {2013},
        booktitle = {In Proceedings of the 3rd International Conference on Social Eco-Informatics (SOTICS)},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-11}
}
          

A concept map is a visual representation of concepts as nodes and of relationships between concepts as edges as a diagram consisting of nodes linked with each other. Concept maps support the learning process inasmuch that they make learners aware of their own progresses. We propose a game-like e-learning tool named Termina to be used for assessing learners’ progresses using which learners can build up their own concept maps and compare them with that of the learners’ community. Deploying Termina within the audience of a university course yields snapshots of the concept maps built while participating in the lecture for both each student as well as for the student’s community. These concept maps are build from the associations that the students provide through participating in Termina sessions. Learners profit from the concept maps’ availability, learn from their fellows and can track their learning process. Lecturers gain insights into the knowledge and ignorance of their students.

@inproceedings{PMS-FB-2013-10,
	author = {Fabian Kneissl and François Bry},
	title = {Fostering Concept Maps Awareness as a Means to Learning},
	booktitle = {Proceedings of the Third International Conference on Social Computing and Its Applications (SCA)},
	year = {2013},
	url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-10}
}

Large infrastructures become technologically more and more complex and interdependencies between different infrastructures increase. As a consequence complex infrastructures become more vulnerable to emergencies. The personnel in charge must be supported in the challenging task of identifying and assessing an emergency situation and in choosing an appropriate reaction. This calls for a system which continuously analyses the available sensory data for emergency situations, making predictions for the future development of an emergency and recommending proper reactions to the emergency.

@article{PMS-FB-2013-9,
	author = {Steffen Hausmann, Simon Brodt, François Bry, and Marco Bettelini},
	title = {Dynamic Emergency Management},
	journal = {Fachzeitschrift für Information Management & Consulting},
	volume = {2},
	year = {2013},
	pages = {36--47},
	url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-9}
}

Complex actions are a natural extension for complex event processing languages needed by many applications like emergency management. In particular interactions with external actuators that are common in those applications pose challenges that need to be adequately covered. Many approaches towards actions and reactivity in event processing are, however, either too simple or too formal to model complex composite actions in a convenient manner or require a complete knowledge of the actions and of their effects. This article proposes a pragmatic yet generic approach to complex actions in event processing which adapts to the heterogeneous and incomplete nature of physical actions. The article furthermore introduces a static semantic analysis for rejecting incorrect and undesirable programs which scales with the available information without requiring an a priori, or complete, knowledge of the actions and their consequences. The article finally describes a transformation of complex actions into complex events queries making it rather simple to add complex actions to a wide range of event processing languages.

@techreport{PMS-FB-2013-8,
	author = {Steffen Hausmann and François Bry},
	title = {Towards Complex Actions for Complex Event Processing},
	institution = {Institute for Informatics, University of Munich},
	type = {Research Report},
	number = {PMS-FB-2013-8},
	year = {2013},
	url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-8}
}

Complex actions are a natural extension for complex event processing languages needed by many applications like emergency management. In particular interactions with external actuators that are common in those applications pose challenges that need to be adequately covered. Many approaches towards actions and reactivity in event processing are, however, either too simple or too formal to model complex composite actions in a convenient manner or require a complete knowledge of the actions and of their effects. This article proposes a pragmatic yet generic approach to complex actions in event processing which adapts to the heterogeneous and incomplete nature of physical actions. The article furthermore introduces a static semantic analysis for rejecting incorrect and undesirable programs which scales with the available information without requiring an a priori, or complete, knowledge of the actions and their consequences. The article finally describes a transformation of complex actions into complex events queries making it rather simple to add complex actions to a wide range of event processing languages.

@inproceedings{PMS-FB-2013-7,
	author = {Steffen Hausmann and François Bry},
	title = {Towards Complex Actions for Complex Event Processing},
	booktitle = {International Conference on Distributed Event-Based Systems},
	pages = {135--146},
    publisher = {ACM},
	year = {2013},
	url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-7}
}

This chapter proposes a novel approach to credit risk rating based upon Network Analysis and enabled by Human Computation. Credit risk rating, which is essential on financial markets, has become difficult with the advent of financial instruments called derivatives and structured notes and of credit management techniques called securitization. The consequences have been dramatic: A widespread improper credit risk rating in the presence of these instruments and techniques has been recognized as a major cause of the financial crisis of 2007-2009 which sparked worldwide recessions. This chapter first proposes to collect risk estimates from debtors and derivatives’ parties and to aggregate these estimates into eigenvector centralities expressing a systemic rating of the credit risk faced by the market’s agents. This rating is shown to hold the promise of overcoming many deficiencies of current credit risk rating. Then, practical and theoretical implications of the proposed approach are discussed. Finally, observing that Human Computation systems and markets are related, it is argued that both Human Computation systems and markets are promising applications for approaches of the kind proposed here.

@incollection{PMS-FB-2013-6,
    author = {François Bry},
    title = {Human Computation-Enabled Network Analysis for a Systemic Credit Risk Rating},
    booktitle = {Handbook of Human Computation},
    publisher = {Springer-Verlag},
    editor = {Pietro Michelucci},
    year = {2013},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-6}
}

This article proposes an approach to rely on the standard operators of relational algebra (including grouping and aggregation) for processing complex event without requiring window specifications. In this way the approach can process complex event queries of the kind encountered in applications such as emergency management in metro networks. This article presents Temporal Stream ALgebra (TSA) which combines the operators of relational algebra with an analysis of temporal relations at compile time. This analysis determines which relational algebra queries can be evaluated against data streams, i.e. the analysis is able to distinguish valid from invalid stream queries. Furthermore the analysis derives functions similar to the pass, propagation and keep invariants in Tucker's et al. "Exploiting Punctuation Semantics in Continuous Data Streams". These functions enable the incremental evaluation of TSA queries, the propagation of punctuations, and garbage collection. The evaluation of TSA queries combines bulk-wise and out-of-order processing which makes it tolerant to workload bursts as they typically occur in emergency management. The approach has been conceived for efficiently processing complex event queries on top of a relational database system. It has been deployed and tested on MonetDB.

@techreport{PMS-FB-2013-5,
        author = {Simon Brodt and François Bry},
        title = {{Analysing Temporal Relations} -- {Beyond Windows, Frames and Predicates}.},
        institution = {Institute for Informatics, University of Munich},
        year = {2012},
        type = {Research Report},
        number = {PMS-FB-2013-5},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-5}
}

Linguistic field research depends on collecting phrases and sentences as well as their geographical and social characteristics. The traditional method of field research –researchers asking questions and filling forms– is time-consuming, costly, and not free of biases. This article presents metropolitalia, a Web-based crowdsourcing platform for linguistic field research aiming at overcoming some of the drawbacks of traditional linguistic field research. metropolitalia is built upon Agora, a market for trading with phrases and speculating on their characteristics in a playful manner. Two games are run under Agora, Borsa Parole and Poker Parole, that aim at collecting complementary data and meta-data: Borsa Parole incites players to express their own knowledge or, rather, beliefs, Poker Parole incites players to make conjectures on the beliefs of others, thus enhancing the primary meta-data collected with Borsa Parole with secondary, or reflexive, meta-data needed for language perception studies. This article describes Agora with both games and reports on first evaluations of the data gathered so far.

@inproceedings{PMS-FB-2013-4,
        author = {François Bry and Fabian Kneissl and Thomas Krefeld and Stephan L\"ucke and Christoph Wieser},
        title = {Crowdsourcing for a Geographical and Social Mapping of Italian Dialects},
        booktitle = {Proceedings of 2nd International Workshop on Social Media for Crowdsourcing and Human Computation, Paris, France (1st May 2013)},
        year = {2013},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-4}
}

This article describes how a semantic search engine has been build from, and still is continuously improved by, a semantic analysis of the "footprints" left by players on the gaming Web platform ARTigo. The Web platform offers several Games With a Purpose (GWAPs) some of which have been specifically designed to collect the data needed for building the artwork search engine. ARTigo is a "tagging ecosystem" of games that cooperate so as to gather a wide range of information on artworks. The ARTigo ecosystem generates a folksonomy saved as 3rd-order tensor, that is a generalization of a matrix, the three orders or dimensions of which represent (1) who (2) tagged an (3) an artwork. The semantic search engine is build using a non-trivial generalization of the well-known, matrix-based, Latent Semantic Analysis (LSA) methods and algorithms. ARTigo is in service for five years and is subject to an active research constantly resulting in new developments, some of which are reported about for the first time in this article.

@inproceedings{PMS-FB-2013-3,
        author = {Christoph Wieser and François Bry and Alexandre B\'erard and Richard Lagrange},
        title = {{ARTigo: Building an Artwork Search Engine With Games and Higher-Order Latent Semantic Analysis

              }},
        year = {2013},
        booktitle = {In Proc. of Disco 2013, Workshop on Human Computation and Machine Learning in Games at HComp 2013},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-3}
}

Linguistic field research depends on collecting phrases and sentences as well as their geographical and social characteristics. Collecting such data is usually done by sending researchers in the field to ask questions and fill forms. This traditional field research is time-consuming, costly, and not free of biases. This demonstration paper presents metropolitalia, a Web-based crowdsourcing platform for linguistic field research aiming at overcoming some of the drawbacks of traditional linguistic field research. metropolitalia is built upon Agora, a market for trading with phrases and speculating on their characteristics (such as geographical spread and gender, age, and level of education of speakers) in a playful manner. Borsa Parole, a first game built upon Agora and presented here, incites players to express their own knowledge or, rather, beliefs and aims at collecting meta-data for language studies. This paper describes Agora and Borsa Parole itself, reports on first evaluations of the data gathered so far, and shows a demonstration of Borsa Parole's use.

@techreport{PMS-FB-2013-2,
        author = {François Bry and Fabian Kneissl and Thomas Krefeld and Stephan L\"ucke and Christoph Wieser},
        title = {A Crowdsourcing Platform for Italian Linguistic Field Research},
        institution = {Institute for Informatics, University of Munich},
        year = {2013},
        type = {Research Report},
        number = {PMS-FB-2013-2},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-2}
}

MapReduce is an implementation of MapReduce which exploits the computing power available in the computers of the users of a web platform by giving tasks to the JavaScript engines of their web browsers. This article describes the implementation of JSMapReduce exploiting HTML 5 features, the heuristics it uses for distributing tasks to workers, and reports on an experimental evaluation of JSMapReduce.

@inproceedings{PMS-FB-2013-1,
        author = {Philipp Langhans and Christoph Wieser and François Bry},
        title = {Crowdsourcing MapReduce: JSMapReduce},
        booktitle = {Proceedings of 2013 International Conference on the World Wide Web, Rio de Janeiro, Brazil (13th--17th May 2013)},
        year = {2013},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2013-1}
}

Enabling non-experts to publish structured or semantic data on the web is an important achievement of the social web and one of the primary goals of the social semantic web. Making this data easily accessible in turn has received only little attention. Querying in semantic wikis typically uses full text search for the textual content and a web query language for the annotations. This has two shortcomings: combined queries over content and annotations are not possible, and users either are restricted to simple but vague keyword queries or have to learn a complex web query language. In this chapter, we present an overview of KWQL, a query language that combines keyword search and web querying. KWQL scales with a users’ experience and the sophistication of its information need by a seamlessly transition from basic keyword queries to precise, sophisticated structured analysis queries. KWQL allows for rich combined queries of full text, metadata, document structure, and annotations. KWQL’s companion language visKWQL eases the authoring of such combined queries further through a set of visual building blocks. The underlying query engine provides the full expressive power of first-order queries, but at the same time can evaluate basic queries at almost the speed of a conventional search engine. Results of a user study suggest validate that users can quickly and with very little training formulate KWQL and visKWQL queries, including structured queries.

@incollection{
	author={Weiand, Klara and Hartl, Andreas and Hausmann, Steffen and Furche, Tim and Bry, François},
	title={Keyword-Based Search over Semantic Data},
	booktitle={Semantic Search over the Web},
	year={2012},
	series={Data-Centric Systems and Applications},
	publisher={Springer},
	pages={159-192},
}

@techreport{PMS-FB-2012-16,
    author = {Simon Brodt and Steffen Hausmann and François Bry},
    title = {Refinement of the implementation of event processing and ECA Rules for SITE},
    institution = {Institute for Informatics, University of Munich},
    year = {2012},
    type = {Research Report},
    number = {PMS-FB-2012-16},
    note = {EMILI Deliverable 4.7},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-16}
}

@techreport{PMS-FB-2012-15,
    author = {Steffen Hausmann and Simon Brodt and François Bry},
    title = {Modularization Mechanisms for ECA rules},
    institution = {Institute for Informatics, University of Munich},
    year = {2012},
    type = {Research Report},
    number = {PMS-FB-2012-15},
    note = {EMILI Deliverable 4.6},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-15}
}

Traditional linguistic field research employs the cost- and time-consuming and possibly biased approach of gathering data by sending out researchers and filling in questionnaires. We improve linguistic field research using crowdsourcing techniques to remedy these issues and open research to a wider audience. On the online platform MetropolItalia, going public in August 2012, Italian native speakers are united to gather and assess linguistic data themselves. We focus on the Italian language because it is currently undergoing a divergence and in this aspect it differs from many other languages. In this article, Borsa Parole, the first game made public on this platform, is described and a short evaluation of its exploitation in a beta phase is presented. Two important requirements of game-based crowdsourcing – motivating enough users and gathering the data wanted – necessary for such a platform are discussed. The game Borsa Parole is shown to fulfil these requirements.

@inproceedings{PMS-FB-2012-14,
        author = {Fabian Kneissl and François Bry},
        title = {MetropolItalia: A Crowdsourcing Platform for Linguistic Field Research},
        booktitle = {Proceedings of the IADIS International Conference WWW/Internet 2012, Madrid, Spain (18th--21st October 2012)},
        year = {2012},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-14}
}

Social Tagging has become a method of choice for enriching data (like pictures) with meta-data which in turn can be used for searching (like retrieving art pictures) or tag recommendations relying on Singular Value Decompositions (SVD) to reduce dimensionality. We observed that social tagging-based search or tag-recommendation is more successful, if several dimensions describing the tagging community (like age, interests, cultural background) are considered. In other words, social tagging-based search calls for higher-order, or tensor-based, SVD instead of standard, matrix-based, SVD. This article reports on a parallelization of higher-order SVD which achieves a significantly better time complexity by comparison to single processor approaches. This time complexity is possible thanks to a careful use of Hestenes' SVD. This article also reports on a first experimental evaluation of the approach for a tag recommendation system.

@inproceedings{PMS-FB-2012-13,
        author = {Philipp Shah and Christoph Wieser and François Bry},
        title = {Parallel Higher-Order SVD for Tag-Recommendations},
        booktitle = {Proceedings of the IADIS International Conference WWW/Internet 2012, Madrid, Spain (18th--21st October 2012)},
        year = {2012},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-13}
}

Backstage is a digital backchannel that is carefully designed for the use in large lecture classes. The goal of Backstage is to support social and active learning in a mainly impersonal and passive learning setting. In classes with a large and anonymous audience, passivity can be a cause of lowered awareness. This paper introduces Backstage and discusses its range of functions in the light of how it contributes to awareness. It furthermore introduces newly conceived concepts by which information are collected and properly displayed in order to help both students and lecturer to gain insight about who is around, what are the kinds of activities the community is engaged in, and what matters in the lecture.

@inproceedings{PMS-FB-2012-12,
    author = {Alexander Pohl and François Bry and Jeannette Schwarz and Marlene Gottstein},
    title = {Sensing the Classroom: Improving Awareness and Self-Awareness of Students with Backstage},
    booktitle = {Proceedings of the International Conference on Interactive and Collaborative Learning},
    year = {2012},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-12}
}

Students and lecturers use computers in lectures. But the standard tools give a rather insufficient structure and support for better learning results. Backstage is an adjustable backchannel environment where students can communicate by microblogs, which they can link to the presenter slides. The lecturer can get feedback by Backstage and place quizzes with an Audience Response System. Backstage is designed to facilitate specific sequences of learning activities and to enhance student motivation with different functions, like asking questions anonymously via microblogs or to rate other students’ questions.

@inproceedings{PMS-FB-2012-11,
    author = {Vera Gehlen-Baum and Alexander Pohl and Armin Weinberger and François Bry},
    title = {Backstage -- Designing a Backchannel for Large Lectures},
    booktitle = {Proceedings of the European Conference on Technology Enhanced Learning, Saarbrücken, Germany (18-21 September 2012)},
    year = {2012},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-11}
}

The ESP Game, like other Games With A Purpose (GWAP), tends to generate "surface semantics" tags. This article first discusses why this is the case, then proposes two approaches called "squaring" and "scripting" to collecting "deep emantics" tags that both consist in deploying the ESP Game in unconventional manners. It also reports on a very positive first experimental evaluation of the two approaches. It finally briefly discusses the relevance of squaring and scripting for other GWAPs than the ESP Game.

@inproceedings{PMS-FB-2012-10,
    author = {François Bry and Christoph Wieser},
	title = {Squaring and Scripting the {ESP} Game: Trimming a {GWAP} to Deep Semantics},
    booktitle = {Proceedings of the International Conf. on Serious Games Development and Applications, Bremen, Germany (26-29 September 2012)},
    year = {2012},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-10}
}

The digital backchannel Backstage aims at supporting active and socially enriched participation in large class lectures by improving the social awareness of both lecturer and students. For this purpose, Backstage provides microblog-based communication for fast information exchange among students as well as from audience to lecturer. Rating enables students to assess relevance of backchannel messages for the lecture. Upon rating a ranking of messages can be determined and immediately presented to the lecturer. However, relevance is of temporal nature. Thus, the relevance of a message should degrade over time, a process called aging. Several aging approaches can be found in the literature. Many of them, however, rely on the physical time which only plays a minor role in assessing relevance in lecture settings. Rather, the actuality of relevance should depend on the progress of a lecture and on backchannel activity. Besides, many approaches are quite difficult in terms of comprehensibility, interpretation and handling. In this article we propose an approach to aging that is easy to understand and to handle and therefore more appropriate in the setting considered.

@inproceedings{PMS-FB-2012-9,
  title = {{Discerning Actuality in Backstage -- Comprehensible Contextual Aging

              }},
  author = {Julia Hadersberger and Alexander Pohl and François Bry},
  booktitle = {Proceedings of the European Conference on Technology Enhanced Learning, Saarbrücken, Germany (18-21 September 2012)},
  year = {2012},
  url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-9}
},

Linguistic field research relies on gathering data on how people express themselves. Traditionally, this is done by sending scientists to interview speakers and to report on these interviews by filling forms. This is a very slow and excessively expensive process which, furthermore, is often biased. Indeed, researchers’ questions and reports are influenced by their -conscious as well as unconscious- preconceptions. Crowdsourcing on the Web is a promising alternative to traditional linguistic field research. This article describes Agora, a market-like social software conceived for Web-based linguistic field research. Agora is the operating system of two distinct social media, Borsa Parole and Poker Parole, both designed to gather qualitative as well as quantitative data on Italian dialects and vernaculars. A specificity of Agora is that it can be deployed both for games and non-game social media. Arguably, Agora can be used for further applications beyond linguistic field research. Its possible application in art history is discussed.

@inproceedings{PMS-FB-2012-8,
    author = {Fabian Kneissl and François Bry},
    title = {Speculation and Bluff for Linguistic Field Research - Social Software and Media for Data Gathering},
    booktitle = {Proceedings of 5. Workshop Digitale Soziale Netze im Rahmen der 42. Jahrestagung der Gesellschaft für Informatik},
    institution = {Institute for Informatics, University of Munich},
    year = {2012},
    month = {September},
    address = {Braunschweig, Germany},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-8}
}

Data stream management systems (DSMS) so far focus on event queries and hardly consider combined queries to both data from event streams and from a database. However, applications like emergency management require combined data stream and database queries. Further requirements are the simultaneous use of multiple timestamps after different time lines and semantics, expressive temporal relations be- tween multiple time-stamps and flexible negation, grouping and aggregation which can be controlled, i. e. started and stopped, by events and are not limited to fixed-size time windows. Current DSMS hardly address these requirements. This article proposes Temporal Stream Algebra (TSA) so as to meet the afore mentioned requirements. Temporal streams are a common abstraction of data streams and data- base relations; the operators of TSA are generalizations of the usual operators of Relational Algebra. A in-depth 'anal- ysis of temporal relations guarantees that valid TSA expres- sions are non-blocking, i. e. can be evaluated incrementally. In this respect TSA differs significantly from previous alge- braic approaches which use specialized operators to prevent blocking expressions on a \syntactical" level.

@techreport{PMS-FB-2012-7,
        author = {Simon Brodt and François Bry},
        title = {Temporal Stream Algebra},
        institution = {Institute for Informatics, University of Munich},
        year = {2012},
        type = {Research Report},
        number = {PMS-FB-2012-7},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-7}
}

Automatic reactions triggered by complex events have been deployed with great success in particular domains, among others, in algorithmic trading, the automatic reaction to realtime analysis of marked data. However, to date, reactions in complex event processing systems are often still limited to mere modifications of internal databases or are realized by means similar to remote procedure calls.
In this paper, we argue that expressive complex actions with support for composite work ows and integration of so called external actions are desirable for a wide range of real-world applications among other emergency management. This article investigates the particularities of external actions needed in emergency management, which are initiated inside the event processing system but which are actually executed by external actuators, and discuss the implications of these particularities on composite actions. Based on these observations, we propose versatile complex actions with temporal dependencies and a seamless integration of complex events and external actions. This article also investigates how the proposed integrated approach towards complex events and complex actions can be evaluated based on simple reactive rules. Finally, it is shown how complex actions can be deployed for a complex event processing system devoted to emergency management.

@techreport{PMS-FB-2012-6,
        author = {Steffen Hausmann and Maximilian Scherr and François Bry},
        title = {Complex Actions for Event Processing},
        institution = {Institute for Informatics, University of Munich},
        year = {2012},
        type = {Research Report},
        number = {PMS-FB-2012-6},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-6}
}

ARTigo is a gaming platform with two goals: The development of a semantic search engine for art works and a study on art work reception. Even though ARTigo quite successfully achieves its goals, it is so far still deficient at collecting “deep semantics” tags. This article first discusses why this is the case, then proposes two approaches we call “squaring” and “scripting” to collecting deep semantic tags that both consist in deploying the ESP Game in unconventional manners. Finally, the relevance of squaring and scripting for other GWAPs than the ESP Game is discussed.

@inproceedings{PMS-FB-2012-5,
    author = {François Bry and Christoph Wieser},
	title = {Squaring and Scripting the {ESP} Game},
    booktitle = {Proceedings of the 4th Human Computation Workshop, Toronto, Canada (23rd July 2012)},
    year = {2012},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-5}
}

This article describes a novel approach to linguistic field research consisting in exploiting the self-regulation of a market for collecting data on language use. The market is conceived as an output-agreement game with a purpose called Borsa Parole. The agreement can be traded with by the players what makes it adjustable. Borsa Parole has been conceived and is deployed for a linguistic study on the divergence of Italian dialects and vernaculars.

@techreport{PMS-FB-2012-4,
    author = {Fabian Kneissl and François Bry},
    title = {Borsa Parole - A Market for Linguistic Speculation},
    institution = {Institute for Informatics, University of Munich},
    year = {2012},
    type = {Research Report},
    number = {PMS-FB-2012-4},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-4}
}

This article is devoted to economical aspects of Human Computation (HC) and to perspectives of HC in economics. As of economical aspects of HC, it is first observed that much of what makes HC systems effective is economical in nature suggesting that complexity being reconsidered as a “HC complexity” and the conception of efficient HC systems as a “HC economics”. This article also points to the relevance of HC in the development of standard software and to the importance of competition in HC systems. As of HC in economics, it is first argued that markets can be seen as HC systems avant la lettre. Looking more closely at financial markets, the article then points to a speed differential between transactions and credit risk awareness that compromises the efficiency of financial markets. Finally, a HC- based credit risk rating is proposed that, overcoming the afore mentioned speed differential, holds promise for better functioning financial markets.

@techreport{PMS-FB-2012-3,
    author = {François Bry},
    title = {Human Computation and Economics},
    institution = {Institute for Informatics, University of Munich},
    year = {2012},
    type = {Research Report},
    number = {PMS-FB-2012-3},
    url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-3}
}

Java2OWL is a Java software library for synchronising Java class hierarchies with OWL concept hierarchies. With a few extra annotations in Java class files, the Java2OWL library can automatically map Java class hierarchies to OWL ontologies. The instances of these Java classes are automatically mapped to OWL individuals and vice versa. OWL reasoners can be used as query processors to retrieve instances of OWL concepts, and these OWL individuals are mapped to corresponding instances of the Java classes. Changes of the Java object's attributes are automatically mapped to changes of the corresponding attributes of the OWL individuals, thus keeping Java and OWL synchronised. With minimal programming overhead the library allows one to combine the power of programming (in Java) with the expressivity and the reasoning power of OWL. This paper introduces the main ideas and techniques. Examples in the appendix illustrate how the system operates. The Java2OWL Application Interface (API) can be found in the Javadoc generated documentation.

@techreport{PMS-FB-2012-2,
        author = {Hans Juergen Ohlbach},
        title = {Java2OWL: A System for Synchronising Java and OWL},
        institution = {Institute for Informatics, University of Munich},
        year = {2012},
        type = {Research Report},
        number = {PMS-FB-2012-2},
        url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2012-2}
}

Contemporary higher education with its large audiences suffers from passivity of students. Enhancing the classroom with a digital backchannel can contribute to establishing and fostering active participation of and collaboration among students in the lecture. Therefore, we conceived the digital backchannel Backstage specifically tailored for the use in large classes. At an early phase of development we tested its core functionalities in a small-scale user study. The aim of the study was to gain first impressions of its adoption, and also to form a basis for further steps in the conception of Backstage. Regarding adoption we particularly focused on how Backstage influences the participants’ questioning behavior, a salient aspect in learning. We observed that during the study much more questions were uttered on Backstage than being asked without backchannel support. Regarding the further development of Backstage we capitalized on the participants' usability feedback. The key of the refinement is the integration of presentation slides in Backstage, which leads to an interesting reconsideration of the user interactions of Backstage.

      @inproceedings{PMS-FB-2012-1,
        title = {{Enhancing the Digital Backchannel Backstage on the Basis of a Formative User Study

              }},
        booktitle = {International Journal of Emerging Technologies in Learning (iJet)},
        author = {Alexander Pohl and Vera Gehlen-Baum and Fran\c{c}ois Bry},
        volume = {7},
        number = {1},
        year = {2012},
        pages = {33--41}
      },
      

Zum Erfolg der relationalen Datenbanken haben ihre logik-basiereten Anfragen deswegen beigetragen, weil sie relativ leicht zu optimieren und auszudrücken sind. Relationale Anfragen eignen sich aber kaum zur Datenextraktion im Web und aus Ereignissströmen und können nicht so gut mit RDF umgehen. Dieser Artikel stellt prototypische Anfragesprachen vor, die das deklarative logik-basierte Paradigma der relationalen Anfragen auf verschiedene Weisen an das Web und an Ereignisströme anpassen: Xcerpt für unvollständige Web-Anfragen, KWQL für ein Spektrum von Web-Anfragetypen von einfachen Schlüsselwort-Anfragen bis hin zu Strukturanfragen, KWRL zur Begründungsverwaltung, XChange^EQ für Ereignisanfragen, RDFLog zur uneingeschränkten Behandlung von Blank Nodes in RDF-Anfragen und RPL für Pfadanfragen in RDF-Graphen.

      @article{PMS-FB-2011-17,
        author    = {Fran\c{c}ois Bry},
        title     = {Anfragesprachen neu erdacht},
        journal   = {KI},
        volume    = {26},
        number    = {1},
        year      = {2012},
        pages     = {15-25},
        ee        = {http://dx.doi.org/10.1007/s13218-011-0149-0}
      }
      

      @techreport{PMS-FB-2011-16,
          author = {Simon Brodt},
          title = {Implementation},
          institution = {Institute for Informatics, University of Munich},
          year = {2011},
          type = {Research Report},
          number = {PMS-FB-2011-16},
          note = {Ph.D. Workshop paper at the Fifth International Conference on Distributed Event-Based Systems (DEBS2011)},
          url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-16}
      }
      

Decision making is typically a well-defined process. The decision is formulated, the decision options are determined and information regarding the options is retrieved by the decision makers. Eventually, the decision is taken by some kind of voting. In this article we propose a novel approach to decision making called liquid decision making (LDM). LDM enables people to incorporate new information, to react to the voting of others, and to reconsider and revise their own voting. Additionally, a competitive element is introduced by basing the decision making mechanism on market principles: Indecision can lead to a loss of influence in the decision making. Artificial market perturbations are used to gauge the stability of a decision suggested by a market equilibrium. This article introduces LDM and its market perturbations and reports on an exploratory study conducted using LDM.

      @inproceedings{PMS-FB-2011-15,
       author = {Stephan Leutenmayr and Fran\c{c}ois Bry},
       title = {Liquid decision making: an exploratory study},
       booktitle = {Proceedings of the 13th International Conference on Information Integration and Web-based Applications and Services},
       series = {iiWAS '11},
       year = {2011},
       location = {Ho Chi Minh City, Vietnam},
       pages = {391--394},
       url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-15},
       publisher = {ACM},
       address = {New York, NY, USA}
      }

      

      @techreport{PMS-FB-2011-14,
          author = {Simon Brodt and Steffen Hausmann and Fran\c{c}ois Bry},
          title = {Implementation},
          institution = {Institute for Informatics, University of Munich},
          year = {2011},
          type = {Research Report},
          number = {PMS-FB-2011-14},
          note = {EMILI Deliverable 4.5},
          url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-14}
      }
      

Semantic optimization of database queries, i.e. the use of metadata for query optimization, is well investigated and has led to significant performance gains. This report shows that semantic optimization of database systems is applicable to Complex Event Processing (CEP) and has even greater potential in this field.
However, in CEP in contrast to database systems, the validity of data and metadata, and the evaluation of queries are dependent from particular time intervals or application states. Many event-based applications have numerous involved workflow determined constraints.
For these reasons, a new kind of CEP metadata, called Instantiating Hierarchical Timed Automata (IHTA), is formally defined in this report. IHTA formalize application states very naturally. They capture complex causal, temporal, cardinality, and data dependencies between events and states. They are modular and represent an arbitrary number of concurrent processes.
To keep IHTA readable, only the workflow determined part of application semantics is captured by them. The rest of the application specific knowledge is expressed by constraints in the Event Stream Constraint Language (ESCL) developed in this work. ESCL constraints are short but expressive first-order logic formulas capturing causal, temporal, cardinality, data, and spatial dependencies between events and states. ESCL has strong formal foundations. Its declarative semantics is defined very similarly to the Tarski model theory. The operational semantics of ESCL is the algorithm semantically rewriting CEP queries with respect to ESCL constraints which is the adaption of the respective algorithm for database systems to CEP. (IHTA will be transformed into ESCL constraints to be used for semantic query optimization by the same algorithm. This transformation is still subject for future work.)
To reduce the number of constraints which must be specified by the user in ESCL directly, ESCL cardinality constraints are propagated from base events (states) to the derived events (states) with respect to the queries deriving them. Propagation of other kinds of ESCL constraints is to be investigated.

      @techreport{PMS-FB-2011-13,
              author = {Olga Poppe},
              title = {{A Method for Semantic Optimization of Complex Event Processing

              }},
              institution = {Institute for Informatics, University of Munich},
              year = {2011},
              type = {Research Report},
              number = {PMS-FB-2011-13},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-13}
      }
      

To reduce the passivity of students in large lectures, we propose to enhance the classroom with the digital backchannel Backstage, which aims at promoting awareness and participation. We tested Backstage in a preliminary user study at a relatively early stage of development. Besides gaining first impressions of usability, we were particularly interested in the kinds of questions raised on Backstage and how they correlate to the participants' attitudes towards questioning. The study confirms known issues regarding questioning that are not fully overcome with the tested prototype. Thus it is concluded that the concept of Backstage needs to be extended in order to embrace remedial assistance in how to ask adequate questions during lectures

      @inproceedings{PMS-FB-2011-12,
        address = {Piestany, Slovakia},
        title = {{Assessing {Backstage--A} Backchannel for Collaborative Learning in Large Classes

              }},
        booktitle = {Proceedings of the 14th International Conference on Interactive Collaborative Learning ({ICL} 2011)},
        author = {Vera Gehlen-Baum and Alexander Pohl and Fran\c{c}ois Bry},
        year = {2011},
        pages = {154-160}
      }
      

Many articles in the last couple of years argued that it is necessary to promote the active participation of students in lectures with large audiences. One approach to make students actively participate in a lecture is to use a digital backchannel, i.e. a computer-mediated communication platform that allows students to exchange ideas and opinions, without disrupting the lecturer’s discourse. Though, a digital backchannel, in order to be most helpful for learning, have to address the need for guidance of the users interacting. The article presents Backstage, a digital backchannel for large class lectures, and shows how it provides guidance for its users, i.e. the students but also the lecturer. Structural guidance is provided by aligning the usually incoherent backchannel discourse with the presentation slides that are integrated in the backchannel’s user interface. The alignment is thereby asserted by carefully designed backchannel workflows. The article also discusses the guidance of a student’s substantial involvement in both the frontchannel and the backchannel by means of scripts. Through the interactions of guided individuals a social guidance may emerge, leading to a collectively regulated backchannel.

      @incollection{PMS-FB-2011-11,
        address = {Badajoz, Spain},
        title = {{Providing Guidance on Backstage, a Novel Digital Backchannel for Large Class Teaching

              }},
        booktitle = {{Education in a Technological World: Communicating Current and Emerging Research and Technological Efforts

              }},
        publisher = {Formatex Research Center},
        url = {http://www.formatex.org/ict/chapters.html}, 
        editor = {A. Mendez-Vilas},
        author = {Daniel Baumgart and Alexander Pohl and Vera Gehlen-Baum and Fran\c{c}ois Bry},
        year = {2012},
        pages = {364--371}
      }
      

This article reports on the conception of a novel digital backchannel, project name Backstage, dedicated to large classes aiming at empowering not only the audience but also the speaker, at promoting the awareness of both audience and speaker, and at promoting an active participation of students in the lecture. The backchannel supports different forms of inter-student communication via short microblog messages, social evaluation and ranking of messages by the students themselves. Backstage allows for the aggregation of student's opinions aiming at supporting the community building of the audience and strengthening the students' awareness of and co-responsibility for the class work. The backchannel further supports immediate concise feedback to the lecturer of selected and aggregated students' opinions making it possible to strengthen the lecturer's awareness for students' difficulties. The backchannel's conception is motivated by learning sciences' findings and theories.

This article is an extended version of (Bry et al., 2011) published at the IADIS International Conference e-Society, held in March 2011 in Avila, Spain.

      @article{PMS-FB-2011-10,
        title = {{Introducing Backstage -- A Digital Backchannel for Large Class Lectures

              }},
        volume = {8},
        number = {3},
        journal = {{Interactive Technology and Smart Education}},
        author = {Alexander Pohl and Vera {Gehlen-Baum} and Fran\c{c}ois Bry},
        year = {2011},
        pages = {186-200}
      }
      

We present several novel methods to compute changes to materialized views in logic databases like those used by rule-based reasoners. Such reasoners have to address the problem of changing axioms in the presence of materializations of derived atoms. Existing approaches have drawbacks: some require to generate and evaluate large transformed programs that are in Datalog^neg while the source program is in Datalog and significantly smaller; some recompute the whole extension of a predicate even if only a small part of this extension is acted by the change. The methods presented in this article overcome these drawbacks and derive additional information useful also for explanation, at the price of an adaptation of the semi-novelve forward chaining.

      @techreport{kotowski2011pp,
          abstract = {We present several novel methods to compute changes to
          materialized views in logic databases like those used by rule-based reasoners.
          Such reasoners have to address the problem of changing axioms
          in the presence of materializations of derived atoms. Existing approaches
          have drawbacks: some require to generate and evaluate large transformed
          programs that are in Datalog: while the source program is in Datalog
          and significantly smaller; some recompute the whole extension of a predicate
          even if only a small part of this extension is acted by the change.
          The methods presented in this article overcome these drawbacks and derive
          additional information useful also for explanation, at the price of an
          adaptation of the semi-novelve forward chaining.},
              author = {Jakub Kotowski and Fran\c{c}ois Bry and Norbert Eisinger},
              title = {A Potpourri of Reason Maintenance Methods -- Incremental View Maintenance Reconsidered},
              year = {2011}
      }
      

Decision markets are social media for decision making where the options to choose from are traded for (with real or play money) by the decision makers. The market equilibrium resulting from the competition between the options offered by sellers and sought for by buyers is interpreted as a collective consent and the relative market prices are interpreted as a ranking of the options. However, on decision markets like on financial markets market equilibrium prices may also arise out of mimicry resulting from either indecision or pure greed. The more the trading behavior is driven by indecision or greed, the less the equilibrium prices reflect genuine preferences. This article proposes a novel approach to decision making. It further describes to rely on artificial perturbations of a market's equilibrium for uncovering indecision or greed on decision markets. Based on the hypothesis that profit seeking is affected by psychological norms that can be activated by context cues and social interaction, an experimental evaluation is proposed that shifts a market's framing between a competitive individualistic and a collaborative communal setting. Social norms in the collaborative communal setting are expected to lessen greed and thus give ways to true preferences: The equilibria of markets with a collaborative communal setting are therefore expected to be less vulnerable to artificial pertubations than those with a competitive individualistic setting. This article describes in a principled manner first the market perturbations, second the experimental evaluation framework.

      @inproceedings{PMS-FB-2011-8,
              author = {Stephan Leutenmayr and Fran\c{c}ois Bry and Tom Schiebler and Felix Brodbeck},
              title = {Work in Progress: Do They Really Mean It? Assessing Decision Market Outcomes},
              booktitle = {Proceedings of 4. Workshop Digitale Soziale Netze im Rahmen der 41. Jahrestagung der Gesellschaft für Informatik},
              year = {2011},
              month = {September},
              address = {Berlin, Germany},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-8}
      }
      

We present PEST, a novel approach to approximate querying of graph-structured data such as RDF that exploits the data's structure to propagate term weights between related data items. We focus on data where meaningful answers are given through the application semantics, e.g., pages in wikis, persons in social networks, or papers in a research network such as Mendeley. The PEST matrix generalizes the Google Matrix used in PageRank with a term-weight dependent leap and allows different levels of (semantic) closeness for different relations in the data, e.g., friend vs. co-worker in a social network. Its eigenvectors represent the distribution of a term after propagation. The eigenvectors for all terms together form a (vector space) index that takes the structure of the data into account and can be used with standard document retrieval techniques. In extensive experiments including a user study on a real life wiki, we show how PEST improves the quality of the ranking over a range of existing ranking approaches.

      @article{PMS-FB-2011-7,
              author = {Klara Weiand and Fabian Knei\ss{}l and Wojciech \L{}obacz and Tim Furche and Fran\c{c}ois Bry},
              title = {PEST: Fast Approximate Keyword Search in Semantic Data using Eigenvector-based Term Propagation},
              journal = {Information Systems},
              year = {2012},
              volume = {37},
              number = {4},
              pages = {372--290},
              issn = {0306-4379},
              doi = {10.1016/j.is.2011.10.004},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-7}
      }
      

Fuzzy matching and ranking are two information retrieval techniques widely used in web search. Their application to structured data, however, remains an open problem. This article investigates how eigenvector-centrality can be used for approximate matching in multi- relation graphs, that is, graphs where connections of many different types may exist. Based on an extension of the PageRank matrix, eigenvectors representing the distribution of a term after propagating term weights between related data items are computed. The result is an index which takes the document structure into account and can be used with standard document retrieval techniques. As the scheme takes the shape of an index transformation, all necessary calculations are performed during index time.

      @article{PMS-FB-2011-6,
              author = {Fran\c{c}ois Bry and Fabian Knei{\ss}l and Klara Weiand and Tim Furche},
              title = {Term-Specific Eigenvector-Centrality in Multi-Relation Networks},
              journal = {Social Network Mining},
              year = {2012},
              volume = {1},
              number = {2},
              pages = {141--159},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-6}
      }
      

We present a novel incremental algorithm to compute changes to materialized views in logic databases like those used by rule-based reasoners. Such reasoners have to address the problem of changing axioms in the presence of materializations of derived atoms. Existing approaches have drawbacks: some require to generate and evaluate large transformed programs that are in Datalog^neg: while the source program is in Datalog and significantly smaller; some recompute the whole extension of a predicate even if only a small part of this extension is afected by the change. The method presented in this article overcomes both drawbacks, arguably at an acceptable price: a slight adaptation of the semi-naive forward chaining.

      @inproceedings{kotowski2011rr,
          abstract = {We present a novel incremental algorithm to compute changes to materialized views in logic databases like those used by rule-based reasoners. Such reasoners have to address the problem of changing axioms in the presence of materializations of derived atoms. Existing approaches have drawbacks: some require to generate and evaluate large transformed programs that are in Datalog^neg: while the source program is in Datalog and significantly smaller; some recompute the whole extension of a predicate even if only a small part of this extension is afected by the change. The method presented in this article overcomes both drawbacks, arguably at an acceptable price: a slight adaptation of the semi-naive forward chaining.},
              author = {Jakub Kotowski and Fran\c{c}ois Bry and Simon Brodt},
              booktitle = {Proceedings of the 5th International Conference on Web Reasoning and Rule Systems},
              day = {23--24},
              keywords = {incremental-maintenance, reasoning, rules, views},
              location = {Galway, Ireland},
              month = aug,
              publisher = {Springer},
              series = {LNCS},
              title = {Reasoning as Axioms Change - Incremental View Maintenance Reconsidered},
              year = {2011}
      }
      

Creating descriptive labels for pictures is an important task with applications in image retrieval, Web accessibility and computer vision. Automatic creation of such labels is difficult, especially for pictures of artworks. "Games With A Purpose" strive to create image descriptions by harnessing the intelligence of human players. Existing implementations are highly successful in terms of player count and number of collected labels, but hardly create comprehensive tag sets containing both general and specific labels. We propose Karido, a new image labeling game designed to collect more diverse tags. This paper describes the design and implementation of the game, along with an evaluation based on data collected during a trial deployment. The game is compared to an existing image labeling game using the same database of images. Results of this evaluation indicate that Karido collects more diverse labels and is fun to play.

      @inproceedings{PMS-FB-2011-4,
              author = {Bartholomäus Steinmayr and Christoph Wieser and Fabian Knei{\ss}l and Fran\c{c}ois Bry},
          title = {Karido: A {GWAP} for Telling Artworks Apart},
              booktitle = {Proceedings of the 16th International Conference on Computer Games},
              year = {2011},
              month = {July},
          address = {Louisville, KY, USA},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-4}
      }
      

Humanities rely on both field research data and databases but rarely have the means necessary for employing them. Crowdsourcing on the Web using social media specifically designed for the purpose offers a promising alternative. This article reports about two endeavors of this kind: enriching an art history database with semantic interpretations and collecting and assessing the regional and social origins of parts of speech for a linguistic investigation. The article motivates and describes the approach and further introduces into the semantic analysis method based on higher-order singular value decomposition specially designed for the project.

      @inproceedings{PMS-FB-2011-3,
              author = {Fran\c{c}ois Bry and Fabian Knei{\ss}l and Christoph Wieser},
              title = {Field Research for Humanities with Social Media: Crowdsourcing and Algorithmic Data Analysis},
              booktitle = {Proceedings of 4. Workshop Digitale Soziale Netze im Rahmen der 41. Jahrestagung der Gesellschaft für Informatik (GI), Berlin, Germany (4th -- 7th October 2011)},
              year = {2011},
              month = {September},
              address = {Berlin, Germany},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-3}
      }
      

This article reports on the conception of a novel digital backchannel, code name Backstage, dedicated to large classes aiming at empowering not only the audience but also the speaker, at promoting the awareness of both audience and speaker, and at promoting an active participation of students in the lecture. The backchannel supports different forms of inter-student communication via short microblog messages, social evaluation and ranking of messages by the students themselves, and aggregation of student's opinions aiming at increasing the students' community feeling, strengthening the students' awareness of and co-responsibility for the class work aiming at promoting the students' participation in the lecture. The backchannel further supports immediate concise feedback to the lecturer of selected and aggregated students' opinions aiming at strengthening the lecturer's awareness for students' difficulties. The backchannel's conception is motivated by learning sciences' findings and theories.

      @inproceedings{PMS-FB-2011-2,
              author = {Fran\c{c}ois Bry and Vera {Gehlen-Baum} and Alexander Pohl},
              title = {Promoting Awareness and Participation in Large Class Lectures: The Digital Backchannel Backstage},
              booktitle = {Proceedings of the {IADIS} Int. Conf. e-society},
              year = {2011},
              month = mar,
              pages = {27--34},
              address = {Spain, Avila},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-2}
      }
      

      @techreport{PMS-FB-2011-1,
              author = {Steffen Hausmann and Simon Brodt and Fran\c{c}ois Bry},
              title = {Dura - Concepts and Examples},
              institution = {Institute for Informatics, University of Munich},
              year = {2011},
              type = {Research Report},
              number = {PMS-FB-2011-1},
              note = {EMILI Deliverable 4.3},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2011-1}
      }
      

RPL (pronounced “ripple”) is the most expressive path language for navigating in RDF graphs proposed to date that can still be evaluated with polynomial combined complexity. RPL is a lean language well-suited for integration into RDF rule languages. This integration enables a limited form of recursion for traversing RDF paths of unknown length at almost no additional cost over conjunctive triple patterns. We demonstrate the power, ease, and efficiency of RPL with two applications on top of the RPL Web interface. The demonstrator implements RPL by transformation to extended nested regular expressions (NREs). For these extended NREs we have implemented an evaluation algorithm with polynomial data complexity. To the best of our knowledge, this demo is the first implementation of NREs (or similarly expressive RDF path languages) with this complexity.

      @inproceedings{PMS-FB-2010-15,
              author = {Harald Zauner and Benedikt Linse and Tim Furche and Fran\c{c}ois Bry},
              title = {A RPL through RDF: Expressive Navigation in RDF Graphs},
              booktitle = {Proceedings of Fourth International Conference on Web Reasoning and Rule Systems, Bressanone/Brixen, Italy (22nd--24th September 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-15}
      }
      

      @techreport{PMS-FB-2010-14,
              author = {Simon Brodt and Steffen Hausmann and Fran\c{c}ois Bry},
              title = {Reactive Rules for Emergency Management},
              institution = {Institute for Informatics, University of Munich},
              year = {2010},
              type = {Research Report},
              number = {PMS-FB-2010-14},
              note = {EMILI Deliverable 4.2},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-14}
      }
      

      @techreport{PMS-FB-2010-13,
              author = {Simon Brodt and Steffen Hausmann and Fran\c{c}ois Bry and Olga Poppe and Michael Eckert},
              title = {A Survey on IT-Techniques for a Dynamic Emergency Management in Large Infrastructures},
              institution = {Institute for Informatics, University of Munich},
              year = {2010},
              type = {Research Report},
              number = {PMS-FB-2010-13},
              note = {EMILI Deliverable 4.1},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-13}
      }
      

      @inproceedings{PMS-FB-2010-12,
              author = {Franziska von dem Bussche and Klara Weiand and Benedikt Linse and Tim Furche and Fran\c{c}ois Bry},
              title = {Not So Creepy Crawler: Crawling the Web with XQuery},
              booktitle = {Proceedings of 3rd Future Internet Symposium, Berlin, Germany (20th--22nd September 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-12}
      }
      

      @inproceedings{PMS-FB-2010-11,
              author = {Andreas Hartl and Klara Weiand and Fran\c{c}ois Bry},
              title = {visKWQL, Visual Keyword Queries for Semantic Data},
              booktitle = {Proceedings of 3rd Future Internet Symposium, Berlin, Germany (20th--22nd September 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-11}
      }
      

      @inproceedings{PMS-FB-2010-10,
              author = {Klara Weiand and Steffen Hausmann and Tim Furche and Fran\c{c}ois Bry},
              title = {KWilt: A Semantic Patchwork for Flexible Access to Heterogeneous Knowledge},
              booktitle = {Proceedings of Fourth International Conference on Web Reasoning and Rule Systems, Bressanone/Brixen, Italy (22nd--24th September 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-10}
      }
      

Abstract Complex Event Processing (CEP) denotes algorithmic methods for deriv- ing higher-level knowledge, or complex events, from a stream of lower-level events in a continuous and timely fashion. High-level Event Query Languages (EQLs) are designed for expressing complex events in a convenient, concise, effective and main- tainable manner. CEP differs fundamentally from traditional database or Web query- ing, as CEP continuously evaluates standing queries against a stream of incoming event data whereas traditional querying evaluates incoming ad hoc queries against (more or less) standing data. However EQLs and traditional query languages share a need for clear formal se- mantics which typically consist of two parts: A declarative semantics specifying what the answer of a query should be and an operational semantics telling how this answer is actually computed. The declarative semantics serves as reference for the operational semantics which is the basis for query evaluation and optimization. While formal semantics is well-understood for traditional query languages it has been rather neglected for EQLs so far. In this chapter we use the EQL XChangeEQ to demonstrate a general, easily transferable approach for defining both, the declar- ative and operational semantics of an EQL. The operational semantics on the one hand, bases on CERA, a tailored variant of relational algebra, and incremantal eval- uation of query plans. Although the basic idea might sound familiar from previous approaches like [3, 12, 16], the way it is realized here is significantly different. The declarative semantics on the other hand, is defined using a Tarski-style model theory with accompanying fixpoint theory.

      @incollection {PMS-FB-2010-9,
         author = {Michael Eckert and Fran\c{c}ois Bry and Simon Brodt and Olga Poppe and Steffen Hausmann},
         title = {Two Semantics for CEP, no Double Talk: Complex Event Relational Algebra (CERA) and Its Application to XChange^{EQ}},
         booktitle = {Reasoning in Event-Based Distributed Systems},
         series = {Studies in Computational Intelligence},
         editor = {Helmer, Sven and Poulovassilis, Alexandra and Xhafa, Fatos},
         publisher = {Springer Berlin / Heidelberg},
         isbn = {978-3-642-19723-9},
         keyword = {Engineering},
         pages = {71-97},
         volume = {347},
         url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-9},
         year = {2011}
      }
      

Abstract Complex Event Processing (CEP) denotes algorithmic methods for mak- ing sense of events by deriving higher-level knowledge, or complex events, from lower-level events in a timely fashion and permanently. At the core of CEP are queries continuously monitoring the incoming stream of "simple" events and recognizing "complex" events from these simple events. Event queries monitoring in- coming streams of simple events serve as specification of situations that manifest themselves as certain combinations of simple events occurring, or not occurring, over time and that cannot be detected solely from one or parts of the single events involved. Special purpose Event Query Languages (EQLs) have been developed for the expression of the complex events in a convenient, concise, effective and maintainable manner. This chapter identifies five language styles for CEP, namely composition operators, data stream query languages, production rules, timed state machines, and logic languages, describes their main traits, illustrates them on a sensor network use case and discusses suitable application areas of each language style.

      @incollection {PMS-FB-2010-8,
         author = {Michael Eckert and Fran\c{c}ois Bry and Simon Brodt and Olga Poppe and Steffen Hausmann},
         title = {A CEP Babelfish: Languages for Complex Event Processing and Querying Surveyed},
         booktitle = {Reasoning in Event-Based Distributed Systems},
         series = {Studies in Computational Intelligence},
         editor = {Helmer, Sven and Poulovassilis, Alexandra and Xhafa, Fatos},
         publisher = {Springer Berlin / Heidelberg},
         isbn = {978-3-642-19723-9},
         pages = {47-70},
         volume = {347},
         url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-8},
         year = {2011}
      }
      

This manifesto explains and stresses the importance of "digital social media", "social software" and "social computing". In particular, it makes the claim that we need a better understanding of how this mix of enabling technology, social behaviour and market practises is challenging our socio-economical and political systems, and puts forward an action plan for the areas of education, fundamental research and applied research, to address these challenges. The goal of this manifesto is to raise awareness for digital social media and to stress the need for research, research funding, and education in a field so far under-represented in public research funding programmes and in education. This manifesto does not cover all aspects of digital social media, or provide a comprehensive treatment of their socio-economical impact. Such issues are beyond the scope of this manifesto. This manifesto is an outcome of a Perspective Workshop held from the 25th to 29th of January 2010 at the research centre Schloss Dagstuhl. The workshop brought together scientists and practitioners from academia and industry, across the fields of social sciences and computer science.

      @inproceedings{PMS-FB-2010-7,
              author = {Fran\c{c}ois Bry and Clemens Cap and Ingo Dahm and Julia Maintz and Sebastian Schaffert},
              title = {Dagstuhl Manifesto: Digital Social Media},
              booktitle = {Proceedings of Perspectives Workshop: Digital Social Networks , Dagstuhl, Germany (24th--29th January 2010)},
              year = {2010},
              number = {1041},
              series = {Dagstuhl Seminar Proceedings},
              publisher = {Schloss Dagstuhl -- Leibniz-Zentrum fuer Informatik},
              address = {Dagstuhl, Germany},
              note = {Perspectives Workshop: Digital Social Networks (http://drops.dagstuhl.de/opus/volltexte/2010/2521)},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-7}
      }
      

We present PEST, a novel approach to approximate querying of structured wiki data that exploits the structure of that data to propagate term weights between related wiki pages and tags. Based on the PEST matrix, eigenvectors representing the distribution of a term after propagation are computed. The result is an index which takes the document structure into account and can be used with standard document retrieval techniques. This article gives a detailed outline of the approach and gives first experimental results showing its viability

      @inproceedings{PMS-FB-2010-6,
              author = {Klara Weiand and Fabian Knei{\ss}l and Tim Furche and Fran\c{c}ois Bry},
              title = {PEST: Term-Propagation over Wiki-Structures as Eigenvector Computation},
              booktitle = {Proceedings of 5th Semantic Wiki Workshop, Heraklion, Crete, Greece (31st May 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-6}
      }
      

Reasoning in wikis has focused so far mostly on expressiveness and tractability and neglected related issues of updates and explanation. In this demo, we show reasoning, explanation, and incremental updates in the KiWi wiki and argue that it is a perfect match for OWL 2 RL reasoning. Explanation nicely complements the "work-in-progress" focus of wikis by explaining how which information was derived and thus helps users to easily discover and remove sources of inconsistencies. Incremental updates are necessary to minimize reasoning times in a frequently changing wiki environment.

      @inproceedings{PMS-FB-2010-5,
              author = {Jakub Kotowski and Fran\c{c}ois Bry},
              title = {A Perfect Match for Reasoning, Explanation and Reason Maintenance: OWL 2 RL and Semantic Wikis},
              booktitle = {Proceedings of 5th Semantic Wiki Workshop, Hersonissos, Crete, Greece (31st May 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-5}
      }
      

Web crawlers are increasingly used for focused tasks such as the extraction of data from Wikipedia or the analysis of social networks like last.fm. In these cases, pages are far more uniformly structured than in the generalWeb and thus crawlers can use the structure of Web pages for more precise data extraction and more expressive analysis. In this demonstration, we present a focused, structure-based crawler generator, the "Not so Creepy Crawler" (nc2). What sets nc2 apart, is that all analysis and decision tasks of the crawling process are delegated to an (arbitrary) XML query engine such as XQuery or Xcerpt. Customizing crawlers just means writing (declarative) XML queries that can access the currently crawled document as well as the metadata of the crawl process. We identify four types of queries that together sufice to realize a wide variety of focused crawlers. We demonstrate nc2 with two applications: The first extracts data about cities from Wikipedia with a customizable set of attributes for selecting and reporting these cities. It illustrates the power of nc2 where data extraction from Wiki-style, fairly homogeneous knowledge sites is required. In contrast, the second use case demonstrates how easy nc2 makes even complex analysis tasks on social networking sites, here exemplified by last.fm.

      @inproceedings{PMS-FB-2010-4,
              author = {Franziska von dem Bussche and Klara Weiand and Benedikt Linse and Tim Furche and Fran\c{c}ois Bry},
              title = {Not So Creepy Crawler: Easy Crawler Generation with Standard XML Queries},
              booktitle = {Proceedings of 2010 International Conference on the World Wide Web, Raleigh, North Carolina, USA (26th--30th April 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-4}
      }
      

KiWi is a semantic Wiki that combines the Wiki philosophy of collaborative content creation with the methods of the Semantic Web in order to enable effective knowledge management. Querying a Wiki must be simple enough for beginning users, yet powerful enough to accommodate experienced users. To this end, the keyword-based KiWi query language (KWQL) supports queries ranging from simple lists of keywords to expressive rules for selecting and reshaping Wiki (meta-)data. In this demo, we showcase visKWQL, a visual interface for the KWQL language aimed at supporting users in the query construction process. visKWQL and its editor are described, and their functionality is illustrated using example queries. visKWQL's editor provides guidance throughout the query construction process through hints, warnings and highlighting of syntactic errors. The editor enables round-tripping between the twin languages KWQL and visKWQL, meaning that users can switch freely between the textual and visual form when constructing or editing a query. It is implemented using HTML, JavaScript, and CSS, and can thus be used in (almost) any web browser without any additional software.

      @inproceedings{PMS-FB-2010-3,
              author = {Andreas Hartl and Klara Weiand and Fran\c{c}ois Bry},
              title = {visKWQL, a Visual Renderer for a Semantic Web Query Language},
              booktitle = {Proceedings of 2010 International Conference on the World Wide Web, Raleigh, North Carolina, USA (26th--30th April 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-3}
      }
      

Knowledge representation and reasoning so far have focused on the ideal ultimate goal, thus stressing logical consistency and semantic homogeneity. On the way to consistent and homogenous knowledge rep- resentation and reasoning, inconsistencies and divergent opinions often have to be dealt with. In this article, a social vision of knoweldge repre- sentation is proposed which accomodates conflicting views that possibly even result in logical inconsistencies; reasoning is used to track divergent, possibly incompatible viewpoints. This approach to knowledge repsresen- tation and reasoning has been developped for a social software, a social semantic wiki.

      @inproceedings{PMS-FB-2010-2,
              author = {Fran\c{c}ois Bry and Jakub Kotowski},
              title = {A Social Vision of Knowledge Representation and Reasoning},
              booktitle = {Proceedings of SOFSEM 2010: 36th International Conference on Current Trends in Theory and Practice of Computer Science, \v{S}pindler\r{u}v Ml\'{y}n, Czech Republic (23rd--29th January 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-2}
      }
      

This article introduces KWQL, spoken "quickel", a rulebased query language for a semantic wiki based on the label-keyword query paradigm. KWQL allows for rich combined queries of full text, document structure, and informal to formal semantic annotations. It offers support for continuous queries, that is, queries re-evaluated upon updates to the wiki. KWQL is not restricted to data selection, but also offers database-like views, enabling "construction", the re-shaping of the selected (meta-)data into new (meta-)data. Such views amount to rules that provide a convenient basis for an admittedly simple, yet remarkably powerful form of reasoning. KWQL queries range from simple lists of keywords or label-keyword pairs to conjunctions, disjunctions, or negations of queries. Thus, queries range from elementary and relatively unspecific to complex and fully specified (meta-)data selections. Consequently, in keeping with the "wiki way", KWQL has a low entry barrier, allowing casual users to easily locate and retrieve relevant data, while letting advanced users make use of its full power.

      @inproceedings{PMS-FB-2010-1,
              author = {Fran\c{c}ois Bry and Klara Weiand},
              title = {Flavours of KWQL, a Keyword Query Language for a Semantic Wiki},
              booktitle = {Proceedings of SOFSEM 2010: 36th International Conference on Current Trends in Theory and Practice of Computer Science, \v{S}pindler\r{u}v Ml\'{y}n, Czech Republic (23rd--29th January 2010)},
              year = {2010},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2010-1}
      }
      

This paper describes the conceptual framework for reason maintenance developed as part of Work Package 2 of the KiWi -- Knowledge in a Wiki EU project.

      @techreport{PMS-FB-2009-17,
              author = {Fran\c{c}ois Bry and Jakub Kotowski},
              title = {Reason Maintenance -- Conceptual Framework},
              institution = {Institute for Informatics, University of Munich},
              year = {2009},
              type = {Research Report},
              number = {PMS-FB-2009-17},
              note = {KIWI Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-17}
      }
      

      @inbook{PMS-FB-2009-16,
              author = {Fran\c{c}ois Bry and Tim Furche and Bruno Marnette and Clemens Ley and Benedikt Linse and Olga Poppe},
              title = {SPARQLog: SPARQL with Rules and Quantification},
              chapter = {},
              pages = {},
              publisher = {},
              type = {{ unknown }},
              year = {2009},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-16}
      }
      

      @inbook{PMS-FB-2009-15,
              author = {Tim Furche and Fran\c{c}ois Bry and Antonius Weinzierl},
              title = {Labeling RDF Graphs for Linear Time and Space Querying},
              chapter = {},
              pages = {},
              publisher = {},
              type = {{ unknown }},
              year = {2009},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-15}
      }
      

      @inbook{PMS-FB-2009-14,
              author = {James Bailey and Fran\c{c}ois Bry and Tim Furche and Sebastian Schaffert},
              title = {Semantic Web Query Languages},
              chapter = {},
              pages = {},
              publisher = {},
              type = {{ unknown }},
              year = {2009},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-14}
      }
      

Good tree search algorithms are a key requirement for inference engines of rule languages. As Prolog exemplifies, inference engines based on traditional uninformed search methods with their well-known deficiencies are prone to compromise declarativity, the primary concern of rule languages. The paper presents a new family of uninformed search algorithms that combine the advantages of the traditional ones while avoiding their shortcomings. Moreover, the paper introduces a formal framework based on partial orderings, which allows precise and elegant analysis of such algorithms.

      @inproceedings{PMS-FB-2009-13,
              author = {Simon Brodt and Fran\c{c}ois Bry and Norbert Eisinger},
              title = {Search for More Declarativity - Backward Reasoning for Rule Languages Reconsidered},
              booktitle = {Web Reasoning and Rule Systems, Proceedings of Third International Conference on Web Reasoning and Rule Systems, Chantilly, Virginia, USA (25th--26th October 2009)},
              year = {2009},
              volume = {5837},
              series = {LNCS},
              pages = {71--86},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-13}
      }
      

One significant effort towards combining the virtues of Web search, viz. being accessible to untrained users and able to cope with vastly heterogeneous data, with those of database-style Web queries is are keyword-based Web query languages. These languages operate essentially in the same setting as XQuery or SPARQL but with an interface for untrained users. Keyword-based query languages trade some of the precision that languages like XQuery enable by allowing to formulate exactly what data to select and how to process it, for an easier interface accessible to untrained users. The yardstick for these languages becomes an easily accessible interface that does not sacrifice the essential premise of database-style Web queries, that selection and construction are precise enough to fully automate data processing tasks. To ground the discussion of keyword-based query languages, we give a summary of what we perceive as the main contributions of research and development on Web query languages in the past decade. This summary focuses specifically on what sets Web query languages apart from their predecessors for databases. Further, this tutorial (1) gives an overview over keyword-based query lan- guages for XML and RDF (2) discusses where the existing approaches succeed and what, in our opinion, are the most glaring open issues, and (3) where, beyond keyword-based query languages, we see the need, the challenges, and the opportunities for combining the ease of use of Web search with the virtues of Web queries.

      @inproceedings{PMS-FB-2009-12,
              author = {Fran\c{c}ois Bry and Tim Furche and Klara Weiand},
              title = {Web Queries: From a Web of Data to a Semantic Web},
              booktitle = {Web Information Systems Engineering - WISE 2009, Proceedings of 10th International Conference on Web Systems Engineering, Pozan, Poland (5th--7th October 2009)},
              year = {2009},
              volume = {5802},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-12}
      }
      

      @inproceedings{PMS-FB-2009-11,
              author = {Fran\c{c}ois Bry and Klara Weiand},
              title = {KWQL, Querying for Social Semantic Software},
              booktitle = {Proceedings of Reasoning Web, Fifth International Summer School 2009, Bressaone, Italy (30th August--4th September 2009)},
              year = {2009},
              note = {(Poster)},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-11}
      }
      

Exposing not only human-centered information, but machine-processable data on the Web is one of the commonalities of recent Web trends. It has enabled a new kind of applications and businesses where the data is used in ways not foreseen by the data providers. Yet this exposition has fractured the Web into islands of data, each in different Web formats: Some providers choose XML, others RDF, again others JSON or OWL, for their data, even in similar domains. This fracturing stifles innovation as application builders have to cope not only with one Web stack (e.g., XML technology) but with several ones, each of considerable complexity. With Xcerpt we have developed a rule- and pattern based query language that aims to give shield application builders from much of this complexity: In a single query language XML and RDF data can be accessed, processed, combined, and re-published. Though the need for combined access to XML and RDF data has been recognized in previous work (including the W3C's GRDDL), our approach differs in four main aspects: (1) We provide a single language (rather than two separate or embedded languages), thus minimizing the conceptual overhead of dealing with disparate data formats. (2) Both the declarative (logic-based) and the operational semantics are unified in that they apply for querying XML and RDF in the same way. (3) We show that the resulting query language can be implemented reusing traditional database technology, if desirable. Nevertheless, we also give a unified evaluation approach based on interval labelings of graphs that is at least as fast as existing approaches for tree-shaped XML data, yet provides linear time and space querying also for many RDF graphs. We believe thatWeb query languages are the right tool for declarative data access in Web applications and that Xcerpt is a significant step towards a more convenient, yet highly efficient data access in a "Web of Data".

      @inbook{PMS-FB-2009-10,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Alexander Pohl and Antonius Weinzierl and Olga Yestekhina},
              title = {Four Lessons in Versality or How Query Languages Adapt to the Web},
              chapter = {},
              pages = {},
              publisher = {},
              type = {{ unknown }},
              year = {2009},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-10}
      }
      

Path query languages have been previously shown to complement RDF rule languages in a natural way and have been used as a means to implement the RDFS derivation rules. RPL is a novel path query language specifically designed to be incorporated with RDF rules and comes in three avors: Node-, edge- and path- flavored expressions allow to express conditional regular expressions over the nodes, edges, or nodes and edges appearing on paths within RDF graphs. Providing regular string expressions and negation, RPL is more expressive than other RDF path languages that have been proposed. We give a compositional semantics for RPL and show that it can be evaluated efficiently, whileseveral possible extensions of it cannot.

      @proceedings{PMS-FB-2009-9,
              title = {The Perfect Match: RPL and RDF Rule Languages},
              year = {2009},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-9}
      }
      

An RDF graph is, at its core, just a set of statements consisting of subjects, predicates and objects. Nevertheless, since its inception practitioners have asked for richer data structures such as containers (for open lists, sets and bags), collections (for closed lists) and reification (for quoting and provenance). Though this desire has been addressed in the RDF primer and RDF Schema specification, they are explicitely ignored in its model theory. In this paper we formalize the intuitive semantics(as suggested by the RDF primer, the RDF Schema and RDF seman- tics specifications) of these compound data structures by two orthogonal extensions of the RDFS model theory (RDFCC for RDF containers and collections, and RDFR for RDF reification). Second, we give a set of entailment rules that is sound and complete for the RDFCC and RDFR model theories. We show that complexity of RDFCC and RDFR entailment remains the same as that of simple RDF entailment.

      @proceedings{PMS-FB-2009-8,
              title = {Model Theory and Entailment Rules for RDF Containers, Collections and Reification},
              year = {2009},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-8}
      }
      

First a new formalism for the analysis of (uninformed) \emph{search methods} is developed. It connects search methods with \emph{partial orderings}. In this way a characterization of the completeness of a search method and easier completeness checks become possible. Moreover it simplifies the formulation and the proof of further features. Second a \emph{new uninformed search algorithm} is presented. It is complete and memory efficient and never re-expands nodes. The algorithm is analysed using the previously developed formalism. Finally advantages of the new method for the \emph{implementation of logic programming languages} are briefly discussed. Especially the efficient processing of (almost) tail recursive progams and the definition of declarative semantics are addressed.

      @techreport{PMS-FB-2009-7,
              author = {Simon Brodt},
              title = {Tree-search, Partial Orderings, and a New Family of Uninformed Algorithms},
              institution = {Institute for Informatics, University of Munich},
              year = {2009},
              type = {Research Report},
              number = {PMS-FB-2009-7},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-7}
      }
      

Event-driven information systems demand a systematic and automatic processing of events. Complex Event Processing (CEP) encompasses methods, techniques, and tools for processing events while they occur, i.e., in a continuous and timely fashion. CEP derives valuable higher-level knowledge from lower-level events; this knowledge takes the form of so called complex events, that is, situations that can only be recognized as a combination of several events.

      @techreport{PMS-FB-2009-6,
              author = {Michael Eckert and Fran\c{c}ois Bry},
              title = {Complex Event Processing (CEP)},
              institution = {Institute for Informatics, University of Munich},
              year = {2009},
              type = {Research Report},
              number = {PMS-FB-2009-6},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-6}
      }
      

Ereignisgesteuerte Informationssysteme benötigen eine systematische und automatische Verarbeitung von Ereignissen. Complex Event Processing (CEP) ist ein Sammelbegriff für Methoden, Techniken und Werkzeuge, um Ereignisse zu verarbeiten während sie passieren, also kontinuierlich und zeitnah. CEP leitet aus Ereignissen höheres, wertvolles Wissen in Form von sog. komplexen Ereignissen, d.h. Situationen die sich nur als Kombination mehrerer Ereignisse erkennen lassen, ab.

      @article{PMS-FB-2009-5,
              author = {Michael Eckert and Fran\c{c}ois Bry},
              title = {Aktuelles Schlagwort: Complex Event Processing (CEP)},
              journal = {Informatik Spektrum},
              year = {2009},
              volume = {32},
              number = {2},
              pages = {163--167},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-5}
      }
      

KiWi is a framework for semantic social software applications that combines the Wiki philosophy with Semantic Web technologies. Applications based on KiWi can therefore leverage i.a. reasoning and versioning to follow both aspects and even go beyond existing technologies. For example, KiWi allows composition of content items, which poses a challenge to the versioning system. In this paper we discuss versioning of composed content items and challenges related to reasoning in collaborative social software, as both topics are concerned with updates on the application state.

      @inproceedings{PMS-FB-2009-4,
              author = {Jakub Kotowski and Stephanie Stroka and Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {Dependency Updates and Reasoning for KiWi},
              booktitle = {},
              year = {2009},
              note = {(Poster)},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-4}
      }
      

This presentation outlines requirements for querying and reasoning in a Social Semantic software context. A unified approach which tightly connects the two technologies is sketched.

      @inproceedings{PMS-FB-2009-3,
              author = {Fran\c{c}ois Bry and Jakub Kotowski and Klara Weiand},
              title = {Querying and reasoning for Social Semantic software},
              booktitle = {Proceedings of 6th European Semantic Web Conference, Heraklion, Greece (31st May--4th June 2009)},
              year = {2009},
              note = {(Poster)},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-3}
      }
      

Traditional wikis excel in collaborative work on emerging content and structure. Semantic Wikis go further by allowing users to expose knowledge in ways suitable for machine processing, e.g. using Semantic Web technologies. The combination of ease of use, support for work in progress and Semantic Web technologies makes Semantic Wikis particularly interesting for knowledge-intensive work areas such as project management and software development. While several Semantic Wikis have been put to practical use, the concepts their users interact with have been little discussed. This position paper explores this issue, showing that the design of a conceptual model is not trivial and showing the repercussions of each design choice. The issue is explored stressing the social aspect of Semantic Wikis.

      @inproceedings{PMS-FB-2009-2,
              author = {Fran\c{c}ois Bry and Michael Eckert and Jakub Kotowski and Klara Weiand},
              title = {What The User Interacts With: Reflections On Conceptual Models For Sematic Wikis},
              booktitle = {Proceedings of 6th European Semantic Web Conference, Heraklion, Greece (31st May--4th June 2009)},
              year = {2009},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-2}
      }
      

Das Thema "Semantic Wikis" als Verknüpfung von Wiki-Konzepten mit semantischen Technologien gewinnt in den letzten Jahren zunehmend an Bedeutung, weil es "soziale Intelligenz" und "künstliche Intelligenz" miteinander verknüpft. Ziel des Artikels ist es, einen Überblick über das Thema Semantic Wikis zu schaffen. Wir gehen dabei insbesondere auch auf Anwendungsfelder ein und geben einen kurzen Vergleich ausgewählter Systeme.

      @inbook{PMS-FB-2009-1,
              author = {Sebastian Schaffert and Fran\c{c}ois Bry and Joachim Baumeister and Malte Kiesel},
              title = {Semantische Wikis},
              chapter = {},
              pages = {245--258},
              publisher = {},
              type = {{ unknown }},
              year = {2009},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2009-1}
      }
      

In the domain of Supervisory Control and Data Acquisition (SCADA), significant challenges reside in the variety of proprietary interfaces and protocols which accompany the components and devices provided by different manufacturers. Centralized supervision and control is hampered by incom- patibility issues and additional costs occur because a number of different systems have to be installed and maintained. The Facility Control Markup Language (FCML) is designed to pro- vide standardized and uniform access to different devices which usually only adhere to proprietary interfaces and protocols. This way, operators of SCADA systems can easily integrate and access additional devices and manufacturers can offer their products to a greater number of customers due to increased interoperability. As an application of the Extensible Markup Language (XML), FCML is designed as an open and extensible standard which can easily be adapted and extended to include requirements of future applications and devices. FCML is not platform dependent, uses open software components and standards, and reduces the resource requirements of Remote Terminal Units (RTUs). One vision subjacent to FCML is that web-based SCADA systems are very promising for a wide range of SCADA applications, for reasons of modularity and ease of deployment.

      @inproceedings{PMS-FB-2008-18,
              author = {Fran\c{c}ois Bry and Bernhard Lorenz and Hans J\"urgen Ohlbach and Martin Roeder and Marc Weinberger},
              title = {The Facility Control Markup Language FCML},
              booktitle = {Proceedings of Second International Conference on the Digital Society, Sainte Luce, Martinique, French Caribbean (10th--15th February 2008)},
              year = {2008},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-18}
      }
      

This paper describes state of the art in reason maintenance with a focus on its future usage in the KiWi project. To give a bigger picture of the field, it also mentions closely related issues such as non-monotonic logic and paraconsistency. The paper is organized as follows: first, two motivating scenarios referring to semantic wikis are presented which are then used to introduce the different reason maintenance techniques.

      @techreport{PMS-FB-2008-17,
              author = {Fran\c{c}ois Bry and Jakub Kotowski},
              title = {Reason Maintenance- State of the Art},
              institution = {Institute for Informatics, University of Munich},
              year = {2008},
              type = {Research Report},
              number = {PMS-FB-2008-17},
              note = {KIWI Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-17}
      }
      

L-DSMS is a Local Data Stream Management System. It is a Java Program which can read an XML-file with a description of a network of processing nodes for streaming data. L-DSMS automatically combines all the processing nodes into a single Java program which then processes the data. L-DSMS has a number of predefined nodes, together with an interface for implementing new processing nodes. The generated network can be remotely monitored and reconfigured by a client, Visu-L-DSMS. An example application of L-DSMS is the transformation of RDS-TMC trac messages into KML, which, in turn, can be visualised by Google Earth.

      @inproceedings{PMS-FB-2008-16,
              author = {Christian H\"ansel and Hans J\"urgen Ohlbach and Edgar-Philipp Stoffel},
              title = {L-DSMS - A Local Data Stream Management System},
              booktitle = {Software Architecture, Proceedings of Second European Conference on Software Architecture, Paphos, Cyprus (29th September--1st October 2008)},
              year = {2008},
              volume = {5292},
              series = {LNCS},
              pages = {298--305},
              note = {Additional Information: https://www.pms.ifi.lmu.de/rewerse-wga1/ldsms/publications/index.htm},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-16}
      }
      

      @inproceedings{PMS-FB-2008-15,
              author = {Alex Kohn and Fran\c{c}ois Bry and Alexander Manta},
              title = {Professional Search: Requirements, Prototype and Preliminary Experience Report},
              booktitle = {Proceedings of Iadis International Conference WWW/Internet, Freiburg, Germany (13th--15th October 2008)},
              year = {2008},
              organization = {IADIS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-15}
      }
      

This paper introduces YASE, a domain-aware search agent with learning capabilities. Initially built for the research community of Roche Penzberg, YASE proved to be superior to standard search engines in the company environment due to the introduction of some simple principles: personalized ranking based on a user's role and organizational embedding, automatic classification of documents by using domain knowledge and learning from search history. While the benefits of the learning feature need more time to be fully realized, the other two principles have proved to be surprisingly powerful.

      @inproceedings{PMS-FB-2008-14,
              author = {Alex Kohn and Fran\c{c}ois Bry and Alexander Manta},
              title = {Exploiting a Company's Knowledge: The Adaptive Search Agent YASE},
              booktitle = {Proceedings of International Conference on Semantic Systems, Graz, Austria (3rd--5th September 2008)},
              year = {2008},
              pages = {166--169},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-14}
      }
      

Evaluation of complex event queries over time involves storing information about those events that are relevant for, i.e., might contribute to, future answers. We call the period of time for which an event or an intermediate result must (at least) be stored its temporal relevance. This paper pioneers a precise definition of temporal relevance and develops a method for statically (i.e., at compile time) determining it. During query evaluation (i.e., at run time), this enables garbage collection of events that become irrelevant as time progresses. Temporal relevance is also important at compile time for cost-based query planning.

      @inproceedings{PMS-FB-2008-13,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {On Static Determination of Temporal Relevance for Incremental Evaluation of Complex Event Queries},
              booktitle = {Distributed event-based systems, Proceedings of 2nd International Conference on Distributed Event-Based Systems, Rome, Italy (1st--4th July 2008)},
              year = {2008},
              volume = {332},
              organization = {ACM},
              pages = {289--300},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-13}
      }
      

Events play an essential role in business processes and some forms of business rules. Often they require detection of complex events, that is, events or situations that cannot be inferred from looking only at single events but that manifest themselves in certain combinations of several events. This entails a natural need for high-level query and reasoning languages for complex events. This position paper explores issues related to the design of such languages.

      @inproceedings{PMS-FB-2008-12,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Rules for Making Sense of Events: Design Issues for High-Level Event Query and Reasoning Languages},
              booktitle = {AI Meets Business Rules and Process Management, Proceedings of AAAI 2008 Spring Symposium, Stanford University/Palo Alto, California, USA (26th March 2008)},
              year = {2008},
              organization = {AAAI},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-12}
      }
      

Various query languages for Web and Semantic Web data, both for practical use and as an area of research in the scientific community, have emerged in recent years. At the same time, the broad adoption of the internet where keyword search is used in many applications, e.g. search engines, has familiarized casual users with using keyword queries to retrieve information on the internet. Unlike this easy-to-use querying, traditional query languages require knowledge of the language itself as well as of the data to be queried. Keyword-based query languages for XML and RDF bridge the gap between the two, aiming at enabling simple querying of semi-structured data, which is relevant e.g. in the context of the emerging Semantic Web. This article presents an overview of the field of keyword querying for XML and RDF. >

      @techreport{PMS-FB-2008-11,
              author = {Klara Weiand and Fran\c{c}ois Bry and Tim Furche},
              title = {Reasoning and Querying -- State of the Art},
              institution = {Institute for Informatics, University of Munich},
              year = {2008},
              type = {Research Report},
              number = {PMS-FB-2008-11},
              note = {KIWI Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-11}
      }
      

We propose XcerptRDF, an extension of the rule based XML query language Xcerpt with language constructs explicitly geared at comfortable querying RDF data, including convenient access to collections, containers, reified statements, and "concise bounded descriptions" for blank nodes. Simulation unification, the formal basis for evaluating Xcerpt queries, is extended to cover the new language constructs and thus to give a formal semantics for XcerptRDF queries. In contrast to previous integration approaches such as XSPARQL or GRDDL that combine an XML query language such as XSLT or XQuery with an RDF query language such as SPARQL, XcerptRDF requires the user to learn only a single language: most language constructs are suciently generic to be applied to both RDF and XML data. XcerptRDF is thus a possible solution to the challenge of versatile data access on the Web which has emerged due to the plethora of data formats already online.

      @inproceedings{PMS-FB-2008-10,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Alexander Pohl},
              title = {XcerptRDF: A Pattern-based Answer to the Versatile Web Challenge},
              booktitle = {Proceedings of 22nd Workshop on (Constraint) Logic Programming, Dresden, Germany (30th September--1st October 2008)},
              year = {2008},
              pages = {27--36},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-10}
      }
      

We introduce the recursive, rule-based RDF query language RDFLog. RDFLog extends previous RDF query languages by arbitrary quantifier alternation: blank nodes may occur in the scop e of all, some, or none of the universal variables of a rule. In addition RDFLog is aware of important RDF features such as the distinction between blank nodes, literals and URIs or the RDFS vocabulary. The semantics of RDFLog is closed (every answer is an RDF graph), but lifts RDF's restrictions on literal and blank node occurrences for intermediary data. We show how to define a sound and complete operational semantics that can be implemented using existing logic programming techniques. Using RDFLog we classify previous approaches to RDF querying along their support for blank node construction and show equivalence between languages with full quantifier alternation and languages with only rules.

      @inproceedings{PMS-FB-2008-9,
              author = {Fran\c{c}ois Bry and Tim Furche and Clemens Ley and Benedikt Linse and Bruno Marnette},
              title = {Taming Existence in RDF Querying},
              booktitle = {Web Reasoning and Rule Systems, Proceedings of International Conference on Web Reasoning and Rule Systems, Karlsruhe, Germany (31st October--1st November 2008)},
              year = {2008},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-9}
      }
      

Simulation unification is a sp ecial kind of unification adapted to retrieving semi-structured data on the Web. This article introduces simulation subsumption, or containment, that is, query subsumption under simulation unification. Simulation subsumption is crucial in general for query optimization, in particular for optimizing pattern-based search engines, and for the termination of recursive rule-based web languages such as the XML and RDF query language Xcerpt. This paper first motivates and formalizes simulation subsumption. Then, it establishes decidability of simulation subsumption for advanced query patterns featuring descendant constructs, regular expressions, negative subterms (or subterm exclusions), and multiple variable occurrences. Finally, we show that subsumption between two query terms can be decided in O(n!n ) where n is the sum of the sizes of both query terms.

      @inproceedings{PMS-FB-2008-8,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse},
              title = {Simulation Subsumption or Déjà vu on the Web},
              booktitle = {Web Reasoning and Rule Systems, Proceedings of International Conference on Web Reasoning and Rule Systems, Karlsruhe, Germany (31st October--1st November 2008)},
              year = {2008},
              series = {LCNS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-8}
      }
      

Various query languages for Web and Semantic Web data, both for practical use and as an area of research in the scientific community, have emerged in recent years. At the same time, the broad adoption of the internet where keyword search is used in many applications, e.g. search engines, has familiarized casual users with using keyword queries to retrieve information on the internet. Unlike this easy-to-use querying, traditional query languages require knowledge of the language itself as well as of the data to be queried. Keyword-based query languages for XML and RDF bridge the gap between the two, aiming at enabling simple querying of semi-structured data, which is relevant e.g. in the context of the emerging Semantic Web. This article presents an over view of traditional query languages for XML and RDF, focused on emerging preeminent exemplars in each field, and contrasts these languages with the field of keyword querying for XML and RDF.

      @inproceedings{PMS-FB-2008-7,
              author = {Klara Weiand and Tim Furche and Fran\c{c}ois Bry},
              title = {Quo Vadis, Web Queries},
              booktitle = {Proceedings of International Workshop on Semantic Web Technologies, Belgrade, Serbia (29th--30th September 2008)},
              year = {2008},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-7}
      }
      

In this paper we propose to apply hierarchical graphs to indoor navigation. The intended purpose is to guide humans in large public buildings and assist them in wayfinding. We start by formally defining hierarchical graphs and explaining the particular benefits of this approach. In the main part, we suggest an algorithm to automatically construct such a multi-level hierarchy from floor plans. The algorithm is guided by the idea to exploit domain-specific characteristics of indoor environments. Besides this, two particular problems are addressed: first, how to incorporate three-dimensional elements in the hierarchy, and second, the need for extending the hierarchy at complex geometrical regions with implicit decision points.

      @inproceedings{PMS-FB-2008-6,
              author = {Edgar-Philipp Stoffel and Korbinian Schoder and Hans J\"urgen Ohlbach},
              title = {Applying Hierarchical Graphs to Pedestrian Indoor Navigation},
              booktitle = {Proceedings of 16th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems, Irvine, California (5th--7th November 2008)},
              year = {2008},
              organization = {ACM},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-6}
      }
      

This paper introduces a generic approach to integrating different kinds of geo-referenced sensor measurements along a physical infrastructure. The underlying core ontology is domain-independent and realized using Semantic Web technologies; it can be specialized for different domains. In particular, railway infrastructures are presented as a case study. Using the physical infrastructure as a common spatial reference system constitutes a central point of the integration, which allows to perform reasoning tasks, such as answering network-related queries (involving measurements from both stationary and mobile sensors). A classification of different query types is presented together with the corresponding algorithms.

      @inproceedings{PMS-FB-2008-5,
              author = {Sebastian Mieth and Florian Fuchs and Edgar-Philipp Stoffel and Diana Wei{\ss}},
              title = {Reasoning on Geo-Referenced Sensor Data in Physical Infrastructures},
              booktitle = {Proceedings of the Workshop "Semantic Web meets Geospatial Applications" at the 11th AGILE International Conferende om Geographic Information Science, Girona, Spain (5th--8th May 2008)},
              year = {2008},
              organization = {AGILE},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-5}
      }
      

In this paper, we tackle the challenging problem of guiding pedestrians in buildings. We propose a conceptual model for indoor environments, based only on regions and their boundaries. It needs to be computed just once. Our approach covers different phenomena, in particular irregular, nonconvex regions which are not trivial. Visibility is modelled implicitly and can be determined efficiently. We illustrate by examples how route descriptions can be derived from the model.

      @inproceedings{PMS-FB-2008-4,
              author = {Edgar-Philipp Stoffel and Hans J\"urgen Ohlbach},
              title = {Versatile Route Descriptions for Pedestrian Guidance in Buildings - Conceptual Model and Systematic Method},
              booktitle = {The European Information Society, Proceedings of 11th AGILE International Conferende om Geographic Information Science, Girona, Spain (5th--8th May 2008)},
              year = {2008},
              organization = {AGILE},
              series = {LNGC},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-4}
      }
      

In den letzten Jahren haben soziale Medien enorm an Bedeutung in Gesellschaft und Wirtschaft hinzugewonnen. Fünf Kernkomponenten sozialer Software können derzeit beschrieben werden: Wikis, Blogs, Netzwerke, Tagging und Online-Märkte haben nicht nur ein großes Potenzial, Zusammenarbeit in Technik und Wissenschaft zu unterstützen und zu verbessern, sie bedeuten auch eine große Herausforderung für etablierte Hierarchien und Traditionen der Wissensgenerierung. Der vorliegende Beitrag diskutiert Erfolgsfaktoren sozialer Medien und deren Vorteile sowie bereits bestehende Anwendungen für Technik und Wissenschaft. Als Referenzpunkt dient dabei das Forschungsprojekt KiWi - Knowledge in a Wiki, in dessen Rahmen ein Prototyp eines semantischen Wikis für eine Nutzung in Technik und Wissenschaft entwickelt wird.

      @article{PMS-FB-2008-3,
              author = {Fran\c{c}ois Bry and Jana Herwig},
              title = {Kreidetafel und Lounge 2.0 -- Der Einzug sozialer Medien in Technik und Wissenschaft},
              journal = {IM -- Fachzeitschrift für Information Management und Consulting},
              year = {2008},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-3}
      }
      

This paper describes a project aiming at enhancing social tagging with reasoning and explanations. So as to keep with the ease of use characteristic of social media, simple explanations are required. A working hypothesis of the work reported in this paper is that simple explanations require simple reasoning. The approach to reasoning presented in this paper is minimalist: First, it precludes involved forms of reasoning such as refutation or excluded middle; second, it does not need (structural) induction. It is furthermore pragmatic: it incorporates negation as failure and an ad hoc and primitive form of paraconsistent reasoning. Because reasoning is kept simple, a simple and intuitive approach to explanation based only on proof trees is possible. This paper outlines the approach to both reasoning and explanations. Finally, it discusses more sophisticated explanation concepts, based on a notion of proof factorization, that are deemed necessary in the application context considered.

      @inproceedings{PMS-FB-2008-2,
              author = {Fran\c{c}ois Bry and Jakub Kotowski},
              title = {Towards Reasoning and Explanations for Social Tagging},
              booktitle = {Explanation-aware Computing 2008, Proceedings of 3rd International Workshop on Explanation-aware Computing, Patras, Greece (21st--22nd July 2008)},
              year = {2008},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-2}
      }
      

RDF data is set apart from relational or XML data by its support of rich existential information in the form of blank nodes. Where SQL null values are always scoped over a single statement, blank nodes in RDF can span over any number of statements and thus can be seen as existentially quantified variables. For RDF querying blank node querying is considered in most query languages, but blank node construction, i.e., the introduction of new blank nodes has been mostly ignored (e.g., in Triple) or treated in a very limited form (e.g., in SPARQL). In this paper, we classify three kinds of blank node in RDF query languages and introduce the recursive, rule-based RDF query language RDFLog. RDFLog is the first RDF query languages with full arbitrary quantifier alternation: blank nodes may occur in the scope of all, some, or none of the universal variables of a rule. RDFLog is also aware of important RDF features such as the distinction between blank nodes, literals and URIs or the RDFS vocabulary.

      @inproceedings{PMS-FB-2008-1,
              author = {Fran\c{c}ois Bry and Tim Furche and Clemens Ley and Benedikt Linse and Bruno Marnette},
              title = {RDFLog: It's like Datalog for RDF},
              booktitle = {Proceedings of 22nd Workshop on (Constraint) Logic Programming, Dresden (30th September--1st October 2008)},
              year = {2008},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2008-1}
      }
      

Reactivity, the ability to detect and react to events, is an essential functionality in many information systems. In particular, Web systems such as online marketplaces, adaptive (e.g., recommender) systems, and Web services, react to events such as Web page updates or data posted to a server. This article investigates issues of relevance in designing high-level programming languages dedicated to reactivity on the Web. It presents twelve theses on features desirable for a language of reactive rules tuned to programming event-driven Web and Semantic Web applications.

      @inproceedings{PMS-FB-2007-23,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Twelve Theses on Reactive Rules for the Web},
              booktitle = {Event Processing, Proceedings of Dagstuhl Seminar 07191: Event Processing, Dagstuhl Castle, Germany (6th--11th May 2007)},
              year = {2007},
              number = {07191},
              series = {Dagstuhl Seminar Proceedings},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-23}
      }
      

In the last years, the Semantic Web has significantly gained momentum, and the amount of RDF data on the Web has been increasing exponentially ever since the publication of the RDF recommendation. A great amount of this data is intermingled with HTML and XML at the help of microformats, embedded RDF and RDF/A. To deal with this situation, the W3C has published an editor's draft soliciting a mechanism called GRDDL, an acronym for Gleaning Resource Descriptions From Dialects of Languages to the problem of extracting Semantic Web information from HTML and XML documents. The idea behind GRDLL is to associate an XML document containing embedded RDF information with one or more transformation programs - which the editor's draft proposes to write in XSLT. These transformation programs are specifically written to extract the RDF information from the document. Moreover, the W3C also published a collection of descriptions of use-cases as a motivation for employing the GRDDL method. One of these use-cases is the scheduling of a meeting between friends who publish their calendars either as hcalendar, embedded RDF1, RDFa or RSS 1.0 on their homepages. In a first step, the XSLT-stylesheets associated with the homepages are used for harvesting the RDF information from the homepages, and the resulting RDF graphs are combined in a single RDF model. In a second step, SPARQL is used to query the RDF data and find a date for the meeting that fits in everybody's schedule. Our system implements this use case in two different manners. The first implementation follows the recommendation of the W3C editor's drafts, employing an XSLT processor and a SPARQL[3] implementation (in our case Jena[2]). The second implementation uses Xcerpt[4, 1], a versatile Web and Semantic Web query language for both processing stages. The implementation of these use-cases uncovers difficulties and challenges in the authoring of GRDDL algorithms in XSLT and also in Xcerpt, and highlights advantages and disadvantages of both approaches.

      @inproceedings{PMS-FB-2007-22,
              author = {Fran\c{c}ois Bry and Tim Furche and Alina Hang and Benedikt Linse},
              title = {GRDDLing with Xcerpt: Learn one, get one free!},
              booktitle = {Proceedings of 4th European Semantic Web Conference, Innsbruck, Austria (3rd--7th June 2007)},
              year = {2007},
              organization = {ESSI},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-22}
      }
      

      @incollection{PMS-FB-2007-21,
              author = {Fran\c{c}ois Bry and Tim Furche and Liviu Badea and Christoph Koch and Sebastian Schaffert and Sacha Berger},
              title = {Querying the Web Reconsidered: Design Principles for Versatile Web Query Languages},
              booktitle = {Semantic Web-Based Information Systems: State-of-the-Art Applications},
              publisher = {},
              year = {2007},
              type = {{ unknown }},
              chapter = {8},
              pages = {190--213},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-21}
      }
      

Even with all the progress in Semantic technology, accessing Web data remains a challenging issue with new Web query languages and approaches appearing regularly. Yet most of these languages, including W3C approaches such as XQuery and SPARQL, do little to cope with the explosion of the data size and schemata diversity and richness on the Web. In this paper we propose a straightforward step toward the improvement of this situation that is simple to realize and yet effective: Advanced module systems that make partitioning of (a) the evaluation and (b) the conceptual design of complex Web queries possible. They provide the query programmer with a powerful, but easy to use high-level abstraction for packaging, encapsulating, and reusing conceptually related parts (in our case, rules) of a Web query. The proposed module system combines ease of use thanks to a simple core concept, the partitioning of rules and their consequences in flexible "stores", with ease of deployment thanks to a reduction semantics. We focus on extending the rule-based Semantic Web query language Xcerpt with such a module system though the same approach can be applied to other (rule-based) languages as well.

      @inproceedings{PMS-FB-2007-20,
              author = {Uwe A{\ss}mann and Sacha Berger and Fran\c{c}ois Bry and Tim Furche and Jakob Henriksson and Jendrik Johannes},
              title = {Modular Web Queries --- From Rules to Stores},
              booktitle = {On the Move to Meaningful Internet Systems 2007: OTM 2007 Workshops, Proceedings of International Workshop on Scalable Semantic Web Knowledge Base Systems, Vilamoura, Algarve, Portugal (25th--30th November 2007)},
              year = {2007},
              volume = {4805/2007},
              series = {LCNS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-20}
      }
      

Semantic Wikis bieten im Vergleich zu herkömmlichen Wikis durch die semantische Annotation eine explizite Repräsentation des beinhalteten Wissens. Diese Erweiterung ermöglicht unter anderem die Verwendung von semantischer Suche, automatischer Deduktion und intelligenter Navigation. Als Anwendungen bieten sich diese Systeme besonders für das verteilte Wissensmanagement und Ontologie Engineering an.

      @article{PMS-FB-2007-19,
              author = {Sebastian Schaffert and Fran\c{c}ois Bry and Joachim Baumeister and Malte Kiesel},
              title = {Aktuelles Schlagwort: Semantic Wiki},
              journal = {Informatik Spektrum},
              year = {2007},
              volume = {30},
              number = {6},
              pages = {434--439},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-19}
      }
      

Once upon a time scientists were experts in their field. They knew not only the "hot questions" but also the scientists involved and the various approaches investigated. More important, they were well informed of novel research results. Gone are these favorable times! Hot issues and active research teams emerge with high pace and being informed within days or even hours might be essential for success. Furthermore, no one can any longer keep an eye on the research publications, patents, and other information that might be relevant for one's research. As a consequence, scientists often feel - and in fact they sometimes are - rather unaware of areas that are of prime importance for their research. High diversity, considerable amounts of information and extremely fast communication are key characteristics of today's research - especially in medical biology. An automatic tracking of technical and scientific information is a way to cope with these aspects of today's research. Such a system is made possible by emerging techniques such as "Semantic Web". This article describes the corner stones of such an "Intelligent Information Portal" currently developed at Roche Diagnostics GmbH for scientists in Pharmaceutical Research. The article stresses the salient aspects of the envisioned system and its focus on personalization/adaptation.

      @inproceedings{PMS-FB-2007-18,
              author = {Alex Kohn and Fran\c{c}ois Bry and Stefan Klostermann and Alexander Manta},
              title = {Concepts for an Intelligent Information Portal in Pharmaceutical Research},
              booktitle = {Proceedings of 3rd International Conference on Semantic Technologies, Graz, Austria (5th--7th September 2007)},
              year = {2007},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-18}
      }
      

Abstract This paper takes three important steps towards constraint-based school timetabling: (i) It proposes a constraint model that covers many important requirements of school timetables by means of global constraints. (ii) It proposes a corresponding problem solver that learns from its earlier faults and restarts to escape non-promising parts of the search space. (iii) By reporting a large-scale computational study, it delivers a proof of concept.

      @article{PMS-FB-2007-17,
              author = {Michael Marte},
              title = {Towards Constraint-Based School Timetabling},
              journal = {Annals of Operations Research, Special Issue on Personnel Scheduling and Planning},
              year = {2007},
              volume = {155},
              number = {1},
              pages = {207--225},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-17}
      }
      

An essential feature in practically usable programming languages is the ability to encapsulate functionality in reusable modules. Modules make large scale projects tractable by humans. For Web and Semantic Web programming, many rule-based languages, e.g. XSLT, CSS, Xcerpt, SWRL, SPARQL, and RIF Core, have evolved or are currently evolving. Rules are easy to comprehend and specify, even for non-technical users, e.g. business managers, hence easing the contributions to the Web. Unfortunately, those contributions are arguably doomed to exist in isolation as most rule languages are conceived without modularity, hence without an easy mechanism for integration and reuse. In this paper a generic module system applicable to many rule languages is presented. We demonstrate and apply our generic module system to a Datalog-like rule language, close in spirit to RIF Core. The language is gently introduced along the EU-Rent use case. Using the Reuseware Composition Framework,the module system for a concrete language can be achieved almost for free, if it adheres to the formal notions introduced in this paper.

      @inproceedings{PMS-FB-2007-16,
              author = {Uwe A{\ss}mann and Sacha Berger and Fran\c{c}ois Bry and Tim Furche and Jakob Henriksson and Paula-Lavinia P\u{a}tr\^anjan},
              title = {A Generic Module System for Web Rule Languages: Divide and Rule},
              booktitle = {Advances in Rule Interchange and Applications, Proceedings of International RuleML Symposium on Rule Interchange and Applications, Orlando, Florida, USA (25th--26th October 2007)},
              year = {2007},
              volume = {4824},
              series = {LNCS},
              pages = {63--77},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-16}
      }
      

The field of complex event processing still lacks formal foundations. In particular, event queries require both declarative and operational semantics. We put forward for discussion a proposal towards formal foundations of event queries that aims at making well-known results from database queries applicable to event queries. Declarative semantics of event queries and rules are given as a model theory with accompanying fixpoint theory. Operational semantics are then obtained by translating the considered queries into relational algebra expressions. We show the suitability of relational algebra for the kind of incremental evaluation usually required for event queries. With the aim of generating further discussion of formal foundations in the research community, we reflect openly upon both strengths and weaknesses of the presented approach.

      @inproceedings{PMS-FB-2007-15,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Towards Formal Foundations of Event Queries and Rules},
              booktitle = {Proceedings of the Second Int. Workshop on Event-Driven Architecture, Processing and Systems, Proceedings of 33rd International Conference on Very Large Data Bases, Vienna, Austria (23rd--27th September 2007)},
              year = {2007},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-15}
      }
      

This paper presents a graph-based spatial model which can serve as a reference for guiding pedestrians inside buildings. We describe a systematic approach to construct the model from geometric data. In excess of the well-known topological relations, the model accounts for two important aspects of pedestrian navigation: firstly, visibility within spatial areas and, secondly, generating route descriptions. An algorithm is proposed which partitions spatial regions according to visibility criteria. It can handle simple polygons as encountered in floor plans. The model is structured hierarchically - each of its elements corresponds to a certain domain concept ('room', 'door', 'floor' etc.) and can be annotated with meta information. This is useful for applications in which such information have to be evaluated.

      @inproceedings{PMS-FB-2007-14,
              author = {Edgar-Philipp Stoffel and Bernhard Lorenz and Hans J\"urgen Ohlbach},
              title = {Towards a Semantic Spatial Model for Pedestrian Indoor Navigation},
              booktitle = {Advances in Conceptual Modeling-Foundations and Applications, Proceedings of 26th International Conference on Conceptual Modeling, Auckland, New Zealand (5th--9th November 2007)},
              year = {2007},
              volume = {4802},
              series = {LNCS},
              pages = {328--337},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-14}
      }
      

This articles submits the thesis that visual data modeling and programming languages are conveniently conceived as rendering, or `styling', of conventional, textual languages. Styling has become a widespread technique with the advent of the Web and of the markup language XML. With XML, application data can be modeled after the application logic regardless of the intended rendering. Rendering of XML documents is specified using style sheet languages like CSS. Provided the styling language offers the necessary functionalities, style sheets can similarly specify a visual rendering of modeling and programming languages. The advantages of the approach are manifold: visualization is achieved in a systematic manner, i.e. the same visualization paradigms can be used for several languages; visual languages necessarily come along with textual counterparts; visual languages are much easier to develop than in ad hoc manners. This article first introduces rather limited extensions to the style sheet language CSS that make it amenable to render data modeling and programming languages as visual languages. Then, it demonstrates the approach on a use case, the experimental logic-based Web query and transformation language Xcerpt. Finally, it is argued that the approach is especially amenable to logic-based languages.

      @inproceedings{PMS-FB-2007-13,
              author = {Sacha Berger and Fran\c{c}ois Bry and Tim Furche and Christoph Wieser},
              title = {Visual Languages: A Matter of Style},
              booktitle = {Proceedings of Workshop on Visual Languages and Logic, Coeur d'Alène, Idaho, USA (23rd September 2007)},
              year = {2007},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-13}
      }
      

      @inbook{PMS-FB-2007-12,
              author = {Fran\c{c}ois Bry},
              title = {Die Informatik oder eine Neuerfindung der Sprache},
              chapter = {},
              pages = {pp.163--177},
              publisher = {Wissenschaftliche Buchgesellschaft (WBG)},
              type = {{ unknown }},
              year = {2007},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-12}
      }
      

Queries for composite events typically involve the four complementary dimensions of event data, event composition, relationships between events (esp. temporal and causal), and accumulating events over time windows for negation and aggregation. We consider a datalog-like rule language for expressing such composite event queries and show that their evaluation can be understood as a problem of incrementally evaluating relational algebra expressions. We then show how temporal relationships between events can be utilized to make the evaluation of joins more efficient by avoiding evaluation of certain subexpressions and by making storage of some intermediate results unnecessary.

      @inproceedings{PMS-FB-2007-11,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Temporal Order Optimizations of Incremental Joins for Composite Event Detection},
              booktitle = {Proceedings of Inaugural Int. Conference on Distributed Event-Based Systems, Toronto, Canada (20th--22nd June 2007)},
              year = {2007},
              publisher = {ACM},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-11}
      }
      

      @proceedings{PMS-FB-2007-10,
              title = {Reasoning Web, Third International Summer School 2007},
              year = {2007},
              editor = {Grigoris Antoniou and Uwe A{\ss}mann and Cristina Baroglio and Stefan Decker and Nicola Henze and Paula-Lavinia P\u{a}tr\^anjan and Robert Tolksdorf},
              publisher = {Springer-Verlag},
              volume = {4636},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-10}
      }
      

Rules play an increasingly important role in a variety of Semantic Web applications as well as in traditional IT systems. As a universal medium for publishing information, the Web is envisioned to become the place for publishing, distributing, and exchanging rule-based knowledge. Realizing the importance and the promise of this vision, W3C has created the Rule Interchange Format Working Group (RIF WG) and chartered it to develop an interchange format for rules in alignment with the existing standards in the Semantic Web architecture stack. However, creating a generally accepted interchange format is by no means a trivial task. First, there are different understandings of what a ``rule'' is. Researchers and practitioners distinguish between deduction rules, normative rules, production rules, reactive rules, etc. Second, even within the same category of rules, systems use different (often incompatible) semantics and syntaxes. Third, existing Semantic Web standards, such as RDF and OWL, show incompatibilities with many kinds of rule languages at a conceptual level. This article discusses the role that different kinds of rule languages and systems play on the Web, illustrates the problems and opportunities in exchanging rules through a standardized format, and provides a snapshot of the current work of the W3C RIF WG.

      @incollection{PMS-FB-2007-9,
              author = {Harold Boley and Michael Kifer and Paula-Lavinia P\u{a}tr\^anjan and Axel Polleres},
              title = {Rule Interchange on the Web},
              booktitle = {Reasoning Web, Third International Summer School 2007},
              publisher = {Springer-Verlag},
              year = {2007},
              volume = {4636},
              type = {{ unknown }},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-9}
      }
      

Reactive rules are used for programming rule-based, reactive systems, which have the ability to detect events and respond to them automatically in a timely manner. Such systems are needed on the Web for bridging the gap between the existing, passive Web, where data sources can only be accessed to obtain information, and the dynamic Web, where data sources are enriched with reactive behavior. This paper presents two possible approaches to programming rule-based, reactive systems. They are based on different kinds of reactive rules, namely Event-Condition-Action rules and production rules. Concrete reactive languages of both kinds are used to exemplify these programming paradigms. Finally the similarities and differences between these two paradigms are studied.

      @incollection{PMS-FB-2007-8,
              author = {Bruno Berstel and Philippe Bonnard and Fran\c{c}ois Bry and Michael Eckert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Reactive Rules on the Web},
              booktitle = {Reasoning Web, Third International Summer School 2007},
              publisher = {Springer-Verlag},
              year = {2007},
              volume = {4636},
              type = {{ unknown }},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-8}
      }
      

This survey article introduces into the essential concepts and methods underlying rule-based query languages. It covers four complementary areas: declarative semantics based on adaptations of mathematical logic, operational semantics, complexity and expressive power, and optimisation of query evaluation. The treatment of these areas is foundation-oriented, the foundations having resulted from over four decades of research in the logic programming and database communities on combinations of query languages and rules. These results have later formed the basis for conceiving, improving, and implementing several Web and Semantic Web technologies, in particular query languages such as XQuery or SPARQL for querying relational, XML, and RDF data, and rule languages like the ``Rule Interchange Framework (RIF)'' currently being developed in a working group of the W3C. Coverage of the article is deliberately limited to declarative languages in a classical setting: issues such as query answering in F-Logic or in description logics, or the relationship of query answering to reactive rules and events, are not addressed.

      @incollection{PMS-FB-2007-7,
              author = {Fran\c{c}ois Bry and Norbert Eisinger and Thomas Eiter and Tim Furche and Georg Gottlob and Clemens Ley and Benedikt Linse and Reinhard Pichler and Fang Wei},
              title = {Foundations of Rule-Based Query Answering},
              booktitle = {Reasoning Web, Third International Summer School 2007},
              publisher = {Springer-Verlag},
              year = {2007},
              volume = {4636},
              type = {{ unknown }},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-7}
      }
      

Immer mehr Daten und Dienste stehen auf dem Web zur Verfügung. Eine Reise zu buchen und von einer anderen Webseite Informationen über das Reiseland einzuholen, erfordert heutzutage jedoch noch sehr viel menschliche Interaktion. Ein Grund ist, dass Computer die Bedeutung (Semantik) der Inhalte auf dem Web nicht "verstehen" und damit nicht intelligent kombinieren können. Dies zu ändern ist Ziel der "Semantic Web" Initiative. Das Europäische Exzellenznetzwerk REWERSE ist ein führendes Projekt im Bereich Reasoning (Schließen) auf dem Semantischen Web. REWERSE entwickelt regel-basierte Sprachen und Anwendungen, um (Semantic) Web Daten intelligent zu verarbeiten, zum Beispiel anzufragen oder automatisch Schlüsse zu ziehen. Neben der Forschung fördert REWERSE auch die Semantic Web Ausbildung, den Technologietransfer und ist aktiv im Bereich Standardisierung von Semantic Web Regeltechnologien. REWERSE wird von der Europäischen Kommission und der Schweiz gefördert und vernetzt über 100 Wissenschaftler aus 14 europäischen Ländern.

      @article{PMS-FB-2007-6,
              author = {Fran\c{c}ois Bry and Uta Schwertel},
              title = {Internet intelligenter - Das Europäische Projekt REWERSE entwickelt regelbasierte Technologien für das Semantische Netz},
              journal = {IM - Fachzeitschrift für Information Management & Consulting},
              year = {2007},
              volume = {22},
              number = {1},
              pages = {85--94},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-6}
      }
      

Reactive Web systems, Web services, and Web-based publish/subscribe systems communicate events as XML messages, and in many cases require composite event detection: it is not sufficient to react to single event messages, but events have to be considered in relation to other events that are received over time. Emphasizing language design and formal semantics, we describe the rule-based query language XChangeEQ for detecting composite events. XChangeEQ is designed to completely cover and integrate the four complementary querying dimensions: event data, event composition, temporal relationships, and event accumulation. Semantics are provided as model and fixpoint theories; while this is an established approach for rule languages, it has not been applied for event queries before.

      @techreport{PMS-FB-2007-5,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Rule-Based Composite Event Queries: The Language XChangeEQ and its Semantics (Extended Version with Appendix)},
              institution = {Institute for Informatics, University of Munich},
              year = {2007},
              type = {Research Report},
              number = {PMS-FB-2007-5},
              note = {contains appendix with proofs},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-5}
      }
      

Reactive Web systems, Web services, and Web-based publish/subscribe systems communicate events as XML messages, and in many cases require composite event detection: it is not sufficient to react to single event messages, but events have to be considered in relation to other events that are received over time. Emphasizing language design and formal semantics, we describe the rule-based query language XChangeEQ for detecting composite events. XChangeEQ is designed to completely cover and integrate the four complementary querying dimensions: event data, event composition, temporal relationships, and event accumulation. Semantics are provided as model and fixpoint theories; while this is an established approach for rule languages, it has not been applied for event queries before.

      @inproceedings{PMS-FB-2007-4,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Rule-Based Composite Event Queries: The Language XChangeEQ and its Semantics},
              booktitle = {Proceedings of First International Conference on Web Reasoning and Rule Systems, Innsbruck, Austria (7th--8th June 2007)},
              year = {2007},
              volume = {4524},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-4}
      }
      

Many data sources on the Web evolve: they change their content over time, typically as reactions to events. Such changes often need to be mirrored in data on other Web nodes: updates need to be propagated. To respond to the need for evolution and reactivity both locally and globally, the language XChange has been developed. We demonstrate its applicability in a concrete scenario of distributed Web sites of a scientific community with mutual data dependencies.

      @inproceedings{PMS-FB-2007-3,
              author = {Fran\c{c}ois Bry and Michael Eckert and Hendrik Grallert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Evolution of Distributed Web Data: An Application of the Reactive Language XChange},
              booktitle = {Proceedings of IEEE 23rd International Conference on Data Engeneering, Istanbul, Turkey (15th--20th April 2007)},
              year = {2007},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-3}
      }
      

RDF plays a prominent role in the vision of the Semantic Web and is used in widespread application such as FOAF, Dublin Core and RSS. Besides querying RDF it is also important to reason about RDF data. Therefore it is desirable to have a language which is capable of both reasoning and querying RDF. We propose the RDF query language rdflog, which is based on logic programming. This allows not only to combine querying and reasoning but also to transfer efficient evaluation techniques of logic programming to the evaluation of RDF query languages. In particular we investigate how tabling and magic set evaluation may be used in this context. The semantics of rdflog may be defined in terms of Herbrand models. We investigate whether the evaluation may be made more efficient by considering only non-redundant answers, called lean answers in the RDF context. Implementing the RDFS entailment rules is easily achieved with our approach by adding the RDFS axioms as rules to a query. In contrast to other rule based RDF query languages we also allow the creation of blank nodes in rule heads.

      @inproceedings{PMS-FB-2007-2,
              author = {Fran\c{c}ois Bry and Tim Furche and Clemens Ley and Benedikt Linse},
              title = {RDFLOG---Taming Existence: A Logic-based Query Language for RDF},
              booktitle = {Proceedings of Deduktionstreffen der GI-Fachgruppe Deduktionssysteme, Koblenz, Germany (26th--27th March 2007)},
              year = {2007},
              note = {(Poster)},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-2}
      }
      

Web queries have been and will remain an essential tool for accessing, processing, and, ultimately, reasoning with data on the Web. With the vast data size on the Web and Semantic Web, reducing costs of data transfer and query evaluation for Web queries is crucial. To reduce costs, it is necessary to narrow the data candidates to query, simplify complex queries and reduce intermediate results. This article describes a static approach to optimization of web queries. We introduce a set of rules which achieves the desired optimization by schema and type based query rewriting. The approach consists in using schema information for removing incompleteness (as expressed by `descendant' constructs and disjunctions) from queries. The approach is presented on the query language Xcerpt, though applicable to other query languages like XQuery. The approach is an application of rules in many aspects---query rules are optimized using rewriting rules based on schema or type information specified in grammar rules.

      @inproceedings{PMS-FB-2007-1,
              author = {Sacha Berger and Fran\c{c}ois Bry and Tim Furche and A. J. H\"ausler},
              title = {Completing Queries: Rewriting of Incomplete Web Queries under Schema Constraints},
              booktitle = {Proceedings of First International Conference on Web Reasoning and Rule Systems, Innsbruck, Austria (7th--8th June 2007)},
              year = {2007},
              volume = {4524},
              series = {LNCS},
              note = {(Short paper)},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2007-1}
      }
      

      @proceedings{PMS-FB-2006-34,
              title = {Reasoning Web, Second International Summer School 2006},
              year = {2006},
              editor = {Pedro Barahona and Fran\c{c}ois Bry and Enrico Franconi and Nicola Henze and Ulrike Sattler},
              publisher = {Springer-Verlag},
              volume = {4126},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-34}
      }
      

This article is firstly an introduction into query languages for the Semantic Web, secondly an in-depth comparison of the languages introduced. Only RDF query languages are considered because, as of the writing of this paper, query languages for other Semantic Web data modeling formalisms, especially OWL, are still an open research issue, and only a very small number of, furthermore incomplete, proposals for querying Semantic Web data modeled after other formalisms than RDF exist. The limitation to a few RDF query languages is motivated both by the objective of an in-depth comparison of the languages addressed and by space limitations. During the three years before the writing of this article, more than three dozen proposals for RDF query languages have been published! Not only such a large number, but also the often immature nature of the proposals makes the focus on few, but representative languages a necessary condition for a non-trivial comparison. For this article, the following RDF query languages have been, admittedly subjectively, selected: Firstly, the "relational" or "pattern-based" query languages SPARQL, RQL, TRIPLE, and Xcerpt; secondly the reactive rule query language Algae; thirdly and last the "navigational access" query language Versa. Although subjective, this choice is arguably a good coverage of the diverse language paradigms considered for querying RDF data. It is the authors' hope and expectation, that this comparison will motivate and trigger further similar studies, thus completing the present article and overcoming its limitation.

      @incollection{PMS-FB-2006-33,
              author = {Tim Furche and Benedikt Linse and Fran\c{c}ois Bry and Dimitris Plexousakis and Georg Gottlob},
              title = {RDF Querying: Language Constructs and Evaluation Methods Compared},
              booktitle = {Reasoning Web, Second International Summer School 2006},
              publisher = {},
              year = {2006},
              volume = {4126},
              type = {{ unknown }},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-33}
      }
      

N-ary conjunctive queries, i.e., queries with any number of answer variables, are the formal core of many Web query languages including XSLT, XQuery, SPARQL, and Xcerpt. Despite a considerable body of research on the optimization of such queries over tree-shaped XML data, little attention has been paid so far to efficient access to graph-shaped XML, RDF, or Topic Maps. We propose the first evaluation technique for n-ary conjunctive queries that applies to both tree- and graph-shaped data and retains the same complexity as the best known approaches that are restricted to tree-shaped data only. Furthermore, the approach treats tree and graph-shaped queries uniformly without sacrificing evaluation complexity on the restricted query class. The core of the evaluation technique is based on dynamic programming using a memoization data structure, called "memoization matrix". It can be populated and consumed in different ways. For each of population and consumption, we propose two resp. three algorithms each having their own advantages. The complexity of the algorithms is compared analytically and experimentally.

      @inproceedings{PMS-FB-2006-32,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Andreas Schr\"oder},
              title = {Efficient Evaluation of n-ary Conjunctive Queries over Trees and Graphs},
              booktitle = {Proceedings of 8th International Workshop on Web Information and Data Mining, Arlington, Virginia, USA (10th November 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-32}
      }
      

Semantic web technologies promise to ease the pain of data and system integration in the life sciences. The semantic web consists of standards such as XML for mark-up of contents, RDF for representation of triplets, and OWL to define ontologies. We discuss three approaches for querying semantic web contents and building integrated bioinformatics applications, which allows bioinformaticians to make an informed choice for their data integration needs. Besides already established approach such as XQuery, we compare two novel rule-based approaches, namely Xcerpt - a versatile XML and RDF query language, and Prova - a language for rule-based Java scripting. We demonstrate the core features and limitations of these three approaches through a case study, which comprises an ontology browser, which supports retrieval of protein structure and sequence information for proteins annotated with terms from the ontology.

      @techreport{PMS-FB-2006-31,
              author = {Loïc Royer and Benedict Linse and Thomas W\"achter and Fran\c{c}ois Bry and Michael Schroeder},
              title = {Querying the semantic web: A case study},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-31},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-31}
      }
      

Many data sources on the Web evolve in the sense that they change their content over time, typically as a reaction to some event. Such changes often need to be mirrored in data on other Web nodes: updates need to be propagated. To respond to the need for evolution and reactivity both locally and globally, the language XChange has been developed. In this work, we demonstrate its applicability to a concrete scenario of distributed Web sites of a scientific community with mutual data dependencies.

      @techreport{PMS-FB-2006-30,
              author = {Fran\c{c}ois Bry and Michael Eckert and Hendrik Grallert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Evolution of Distributed Web Data: An Application of the Reactive Language XChange},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-30},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-30}
      }
      

Nowadays events are omnipresent and exchanged as messages over networks. Characteristic for applications involving advanced (or complex) event processing is the need to (1) utilize data contained in the events, (2) detect patterns made up of multiple events (so-called composite events), (3) reason about temporal and causal relationships of events, (4) accumulate events for negation and data aggregation. This article describes a high-level language approach for expressing queries to events. Its foundations are: embedding of a query language for XML and other Web data formats, support for rule-based reasoning, and a complete coverage of the four dimensions mentioned above.

      @inproceedings{PMS-FB-2006-29,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {A High-Level Query Language for Events},
              booktitle = {Proceedings of The First International Workshop on Event-driven Architecture, Processing and Systems (EDA-PS'06) at the 2006 IEEE International Conference on Web Services, Chicago, IL, USA (18th September 2006)},
              year = {2006},
              organization = {IEEE},
              pages = {31--38},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-29}
      }
      

This article describes a particular use of ontologies for visualising maps in a browser window. Geographic data are represented as instances of concepts in an ontology of transportation networks which was designed in close relation to GDF. These data are transformed into SVG, whereas the transformation is specified symbolically as instances of a transformation ontology. This approach is extremely flexible and easily extendible to include all kinds of information in the generated maps. The basic implementation technique is to use classes and instances of ontologies in an intelligent way.

      @inproceedings{PMS-FB-2006-28,
              author = {Frank Ipfelkofer and Bernhard Lorenz and Hans J\"urgen Ohlbach},
              title = {Ontology Driven Visualisation of Maps with SVG - An Example for Semantic Programming},
              booktitle = {Information Visualization, Proceedings of 10th International Conference on Information Visualisation, London, Great Britain (5th--7th July 2006)},
              year = {2006},
              pages = {424--429},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-28}
      }
      

As applications continue to evolve from stand-alone applications in static scenarios to distributed mobile applications which extensively interact with each other and human users in an increasingly dynamic and mobile environment, the context of use becomes ever more important (e.g. time and location, device and user profiles, and other factors). Applications need to have an understanding of the context in form of a comprehensive world model. At the same time as requirements grow, applications have to cope with all kinds of technical restrictions, especially regarding computing power, memory, input/output capabilities, and bandwidth. Powerful infrastructure often cannot be directly accessed and/or made use of in a mobile context in the same way as is possible on a desktop system. Therefore, a suitable world model must be as simple as possible while still offering enough structural depth to carry out geospatial and geotemporal tasks, such as path planning or scheduling appointments. In geospatial modelling two paradigms exist predominantly: qualitative and quantitative. Qualitative methods are closely related to the way humans reason, quantitative methods are more akin to machine reasoning. In this paper we propose a hybrid model which integrates quantitative and qualitative methods in order to facilitate multi-paradigm reasoning, to some extend on incomplete and/or imprecise data. The model is intended for indoor scenarios, such as described in the next section, and is based on a graph structure enriched by meta data. The key idea is to support quantitative information by a qualitative base structure. This paper is a short version of a forthcoming technical report (Lorenz, Ohlbach and Stoffel, 2006).

      @inproceedings{PMS-FB-2006-27,
              author = {Bernhard Lorenz and Hans J\"urgen Ohlbach},
              title = {A Hybrid Model for Indoor Spatial Reasoning},
              booktitle = {Proceedings of First International Workshop on Mobile Geospatial Augmented Reality, Banff, Alberta, Canada (29th--30th May 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-27}
      }
      

This paper serves two purposes. The first purpose is to introduce a new approach for defining point--interval and interval--interval relations for fuzzy time intervals. The basic idea for the interval--interval relations is to extend corresponding point--interval relations to interval--interval relations by averaging (integrating) the point--interval relation over the second interval. The new approach is compared with an existing approach by Nagypal and Motik. The second purpose is to show how these relations can be easily defined with the GeTS language (GeTS stands for GeoTemporal Specifications). This is a typed functional language with a large number of built--in data types and functions for manipulating temporal notions. The definitions of the point--interval and interval--interval relations are therefore given directly in the GeTS language.

      @techreport{PMS-FB-2006-26,
              author = {Hans J\"urgen Ohlbach},
              title = {Relations Between Fuzzy Time Intervals},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-26},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-26}
      }
      

Dieser Vortrag ist den Regelsprachen (oder logischen Sprachen) gewidmet, die zur Verwirklichung des Semantischen Web benötigt werden. Der Vortrag stellt zehn Thesen auf, die nacheinander die folgenden Themen behandeln: 1. Die verschiedenen Arten von Regelsprachen oder logischen Sprachen, die das Semantische Web benötigt. 2. Die Daten, die diese Sprachen bearbeiten, und die Datenverarbeitung, die mit diesen Sprachen ermöglicht oder erleichtert werden sollen. 3. Die Semantik dieser Sprachen. 4. Die Realisierung dieser Sprachen und die Wiedergabe von Programmen in diesen Sprachen.

      @inproceedings{PMS-FB-2006-25,
              author = {Fran\c{c}ois Bry},
              title = {Thesen über Regelsprachen für das semantische Web},
              booktitle = {Proceedings of 18. Workshop Grundlagen von Datenbanken 2006, Wittenberg, Deutschland (6th--9th June 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-25}
      }
      

Diese Vorführung stellt die Anfragesprachen Xcerpt und visXcerpt, siehe http://xcerpt.org vor. Xcerpt ist eine textuelle Anfragesprache, visXcerpt ist eine visuelle Anfragesprache, die als Visualisierung von textuellen Xcerpt-Programmen konzipiert wurde. Xcerpt und visXcerpt sind mit dem Ziel konzipiert worden, innerhalb des selben Anfrageprogramms Daten in den Datenformaten des Webs XML (u.a. HTML) und des Semantischen Webs RDF und Topic Maps anzufragen.

      @inproceedings{PMS-FB-2006-24,
              author = {Sacha Berger and Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Andreas Schr\"oder},
              title = {Vorführung von Xcerpt und visXcerpt, Anfragesprachen für das Web},
              booktitle = {Proceedings of 18. Workshop Grundlagen von Datenbanken 2006, Wittenberg, Germany (6th--9th June 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-24}
      }
      

This paper has been triggered by questions frequently posed by fellow researchers such as: "How for a researcher, or a research team, to get a good Google rank?", "How to make research results visible on the Web?", and "What should scientists publish on the Web?" This paper aims at giving practical answers to these questions understandable without technical knowledge. This paper first argues that the cyberspace is a premier place in todays making of science. Then, it discusses the importance of scientific publishing in the cyberspace. Finally, it describes ways, that in the author's opinion are not unethical, to improve scientific Web pages' Google rankings.

      @techreport{PMS-FB-2006-23,
              author = {Fran\c{c}ois Bry},
              title = {Footprints in Cyberspace -- Research and Researchers' Visibility in the Google Age},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-23},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-23}
      }
      

Event-Condition-Action (ECA) rules offer a flexible, adaptive, and modular approach to realizing business processes. This article discusses the use of ECA rules for describing business processes in an executable manner. It investigates the benefits one hopes to derive from using ECA rules and presents the challenges in realizing business processes. These constitute a list of requirements for an (executable) business process description language, and we take them as a basis to investigate suitability of the concrete ECA rule language XChange in realizing a business process from the EU-Rent Case Study.

      @inproceedings{PMS-FB-2006-22,
              author = {Fran\c{c}ois Bry and Michael Eckert and Paula-Lavinia P\u{a}tr\^anjan and Inna Romanenko},
              title = {Realizing Business Processes with ECA Rules: Benefits, Challenges, Limits},
              booktitle = {Proceedings of 4th Workshop on Principles and Practice of Semantic Web Reasoning, Budva, Montenegro (10th--11th June 2006)},
              year = {2006},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-22}
      }
      

Applications and services that access Web data are becoming increasingly more useful and wide-spread. Current main-stream Web query languages such as XQuery, XSLT, or SPARQL, however, focus only on one of the different data formats available on the Web. In contrast, Xcerpt is a versatile semi-structured query language, i.e., a query language able to access all kinds of Web data such as XML and RDF in the same language reusing common concepts and language constructs. To integrate heterogeneous data and as a foundation for Semantic Web reasoning, Xcerpt also provides rules. Xcerpt has a visual companion language, visXcerpt, that is conceived as a mere rendering of the (textual) query language Xcerpt using a slightly extended CSS. Both languages are demonstrated along a realistic use case integrating XML and RDF data highlighting interesting and unique features. Novel language constructs and optimization techniques are currently under investigation in the Xcerpt project (cf. http://xcerpt.org).

      @inproceedings{PMS-FB-2006-21,
              author = {Sacha Berger and Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Andreas Schr\"oder},
              title = {Beyond XML and RDF: The Versatile Web Query Language Xcerpt},
              booktitle = {Proceedings of 15th Int'l World Wide Web Conference, Edinburgh, Scotland (23rd--26th May 2006)},
              year = {2006},
              pages = {1053--1054},
              note = {Poster Paper},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-21}
      }
      

Query languages for semi-structured data on the Web in the form of XML or RDF have become an essential part of many applications and services. N-ary conjunctive queries, i.e., queries with any number of answer variables, are the formal core of most Web query languages including XSLT, XQuery, SPARQL, and Xcerpt. Despite a considerable body of research on the optimization of such queries against tree-shaped XML data, little attention has been paid so far to efficient access to graph-shaped XML, RDF, or Topic Maps. We propose a novel evaluation technique for n-ary conjunctive queries that applies to both tree- and graph-shaped data. It has the same complexity as the best known approaches that are restricted to tree-shaped data only. The core of the evaluation technique is a memoization data structure, called "memoization matrix", which holds (intermediary) results. It can be populated and consumed in different ways. For both, population and consumption, we propose two algorithms, each having its own advantages. The complexity of the algorithms is compared analytically and experimentally.

      @techreport{PMS-FB-2006-20,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Andreas Schr\"oder},
              title = {Efficient Evaluation of n-ary Conjunctive Queries over Trees and Graphs},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-20},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-20}
      }
      

As the Semantic Web is gaining momentum, the need for truly versatile query languages becomes increasingly apparent. A Web query language is called versatile if it can access in the same query pro- gram data in different formats (e.g. XML and RDF). Most query lan- guages are not versatile: they have not been specifically designed to cope with both worlds, providing a uniform language and common constructs to query and transform data in various formats. Moreover, most of them do not provide a flexible data model that is powerful enough to nat- urally convey both Semantic Web data formats (especially RDF and Topic Maps) and XML. This article highlights challenges related to the data model and language constructs for querying both standard Web and Semantic Web data with an emphasis on facilitating sophisticated reasoning. It is shown that Xcerpt'ss data model and querying constructs are particularly well-suited for the Semantic Web, but that some adjust- ments of the Xcerpt syntax allow for even more effective and natural querying of RDF and Topic Maps.

      @inproceedings{PMS-FB-2006-19,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse},
              title = {Data Model and Query Constructs for Versatile Web Query Languages: State-of-the-Art and Challenges for Xcerpt},
              booktitle = {Proceedings of 4th Workshop on Principles and Practice of Semantic Web Reasoning, Budva, Montenegro (10th--11th June 2006)},
              year = {2006},
              volume = {4187},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-19}
      }
      

Web query languages promise convenient and efficient access to Web data such as XML, RDF, or Topic Maps. Xcerpt is one such Web query language with strong emphasis on novel high-level constructs for effective and convenient query authoring, particularly tailored to versatile access to data in different Web formats such as XML or RDF. However, so far it lacks an efficient implementation to supplement the convenient language features.AMaχoS is an abstract machine implementation for Xcerpt that aims at efficiency and ease of deployment. It strictly separates compilation and execution of queries: Queries are compiled once to abstract machine code that consists in (1) a code segment with instructions for evaluating each rule and (2) a hint segment that provides the abstract machine with optimization hints derived by the query compilation. This article summarizes the motivation and principles behind AMaχoS and discusses how its current architecture realizes these principles.

      @inproceedings{PMS-FB-2006-18,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse},
              title = {AMaχoS - Abstract Machine for Xcerpt: Architecture and Principles},
              booktitle = {Proceedings of 4th Workshop on Principles and Practice of Semantic Web Reasoning, Budva, Montenegro (10th--11th June 2006)},
              year = {2006},
              volume = {4187},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-18}
      }
      

Access to Web data has become an integral part of many ap- plications and services. In the past, such data has usually been accessed through human-tailored HTML interfaces. Nowadays, rich client inter- faces in desktop applications or, increasingly, in browser-based clients ease data access and allow more complex client processing based on XML or RDF data retrieved through Web service interfaces. Convenient spec- ifications of the data processing on the client and flexible, expressive service interfaces for data access become essential in this context. Web query languages such as XQuery, XSLT, SPARQL, or Xcerpt have been tailored specifically for such a setting: declarative and efficient access and processing of Web data. Xcerpt stands apart among these languages by its versatility, i.e., its ability to access not just one Web format but many. In this demonstration, two aspects of Xcerpt are illustrated in detail: The first part of the demonstration focuses on Xcerpt'ss pattern matching con- structs and rules to enable effective and versatile data access. It uses a concrete practical use case from bibliography management to illustrate these language features. Xcerpt'ss visual companion language visXcerpt is used to provide an intuitive interface to both data and queries. The second part of the demonstration shows recent advancements in Xcerpt's implementation focusing on experimental evaluation of recent complexity results and optimization techniques, as well as scalability over a number of usage scenarios and input sizes.

      @techreport{PMS-FB-2006-17,
              author = {Sacha Berger and Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Andreas Schr\"oder},
              title = {Efficient and Effective Data Access in the Versatile Web Query Language Xcerpt},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-17},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-17}
      }
      

Access to Web data has become an integral part of many applications and services. In the past, such data has usually been accessed through human-tailored HTML interfaces. Nowadays, data is more and more served in (syntactically and semantically) richer data formats such as XML and RDF that can be conveniently accessed and processed with Web query languages. However, ordinary Web query languages such as XQuery, XSLT, and SPARQL focus on a single Web format. Xcerpt goes beyond these languages and provides versatile access to data in different Web formats within the same query. This article highlights Xcerpt's essential principles and features.

      @incollection{PMS-FB-2006-16,
              author = {Sacha Berger and Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Sebastian Schaffert},
              title = {The Web and Semantic Web Query Language Xcerpt},
              booktitle = {AIS SIGSEMIS and OSR Semantic Web Fact Book 2005},
              publisher = {},
              year = {2006},
              type = {{ unknown }},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-16}
      }
      

Applications and services that access Web data are becoming increasingly more useful and wide-spread. Web query languages provide efficient and effective means to access and process data published on the Web. Conventional Web query languages such as XQuery, XSLT, or SPARQL, however, focus only on one of the different data formats used on the Web and provide little to ease the integration of heterogeneous schemata or representations. Xcerpt is a versatile semi-structured query language, i.e., a query language able to access all kinds of Web data such as XML and RDF in the same language reusing common concepts and language constructs. In this article, we demonstrate how Xcerpt's features ease the integration of data sources that are heterogeneous in (a) data format (e.g., XML vs. RDF), (b) schema, and (c) concrete representation (if the schema allows representational variants). The results show that versatile Web query languages form a convenient foundation for data integration scenarios on the Web and suggest further consideration of their use in developing data-centric Web applications.

      @inproceedings{PMS-FB-2006-15,
              author = {Fran\c{c}ois Bry and Tim Furche and Benedikt Linse},
              title = {Let's Mix It: Versatile Access to Web Data in Xcerpt},
              booktitle = {Proceedings of 3rd Workshop on Information Integration on the Web, Edinburgh, Scotland (22nd May 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-15}
      }
      

Access to Web data has become an integral part of many applications and services. In the past, such data has usually been accessed through human-tailored HTML interfaces. Nowadays, rich client interfaces in desktop applications or, increasingly, in browser-based clients ease data access and allow more complex client processing based on XML or RDF data retrieved through Web service interfaces. Convenient specifications of the data processing on the client and flexible, expressive service interfaces for data access become essential in this context. Web query languages such as XQuery, XSLT, SPARQL, or Xcerpt have been tailored specifically for such a setting: declarative and efficient access and processing of Web data. This tutorial introduces, compares, and classifies the most relevant exemplars of Web query languages for XML, RDF, and/or TopicMaps data. Interesting features as well as differences in expressiveness and adequacy are digested along practical and concrete use cases. Emphasis is placed on recent W3C standardization activities, contrasted with alternative approaches from industry and academia.

      @inproceedings{PMS-FB-2006-14,
              author = {James Bailey and Fran\c{c}ois Bry and Tim Furche and Benedikt Linse and Paula-Lavinia P\u{a}tr\^anjan and Sebastian Schaffert},
              title = {Rich Clients need Rich Interfaces: Query Languages for XML and RDF Access on the Web},
              booktitle = {Proceedings of 4th German XML-Tage, Berlin, Germany (25th--27th May 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-14}
      }
      

In this article we propose a hybrid spatial model for indoor environments. The model consists of hierarchically structured graphs with typed edges and nodes. The model is hybrid in the sense that nodes and edges can be labelled with qualitative as well as quantitative information. The graphs support wayfinding and, in addition, provide helpful information for generating human-oriented descriptions of an indoor (and outdoor) path.

      @inproceedings{PMS-FB-2006-13,
              author = {Bernhard Lorenz and Hans J\"urgen Ohlbach and Edgar-Philipp Stoffel},
              title = {A Hybrid Model for Representing Indoor Environments},
              booktitle = {Proceedings of 6th International Symposium on Web and Wireless Geographical Information Systems, Hong Kong, China (4th--5th December 2006)},
              year = {2006},
              series = {LNCS},
              pages = {102--112},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-13}
      }
      

This paper contains a brief overview of the `Geo-Temporal' specification language GeTS. The objects which can be described and manipulated with this language are time points, crisp and fuzzy time intervals and labelled partitionings of the time axis. The partitionings are used to represent periodic temporal notions like months, semesters etc. and also whole calendar systems. GeTS is essentially a typed functional language with a few imperative constructs and many built-ins. GeTS can be used to specify and compute with many different kinds of temporal notions, from simple arithmetic operations on time points up to complex fuzzy relations between fuzzy time intervals. A parser, a compiler and an abstract machine for GeTS is implemented.

      @inproceedings{PMS-FB-2006-12,
              author = {Hans J\"urgen Ohlbach},
              title = {GeTS - A Specification Language for Geo-Temporal Notions},
              booktitle = {Proceedings of 29th Annual German Conference on Artificial Intelligence, Bremen, Germany (14th--19th June 2006)},
              year = {2006},
              pages = {214--228},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-12}
      }
      

The key notion for modelling calendar systems and many other periodic temporal notion is the mathematical concept of a partitioning of the real numbers. A partitioning of R splits the time axis into a sequence of intervals. Basic time units like seconds, minutes, hours, days, weeks, months, years etc. can all be represented as partitionings of R with finite partitions. Besides the basic time units in calendar systems, there are a lot of other temporal notions which can be modelled as partitions: the seasons, the ecclesiastical calendars, financial years, semesters at universities, the sequence of sunrises and sunsets, the sequence of the tides, the sequence of school holidays etc. Almost all systems for modelling periodic temporal notions developed so far identify partitions, granules or whatever they are called, by labels or coordinates which are essentially sequences of integers. In this paper it is show how these integer coordinates as identifiers for partitions can be generalised to `partition access specifiers'. An example for a non-trivial partition access specifier is a path in a tree which represents hierarchically nested partitions. A bus timetable, for example, can be specified this way: '(in very winter, in every week, (in day 0-4, hour 5, minute 20, bus B1, hour 6, minute 20 bus B2 ...), (in day 5-6, hour 8, minute 20 bus B1, ...)), (in every spring ...)...'. A particular `partition access specifiers' is then a sequence of integers '10/1/2/..'. The first integer represents an absolute coordinate (season 10). The other integers represent shifts: 1 week after the start of season 10, 2 days after the start of this week etc. The main data structures and algorithms for these `tree partitionings' are presented in this paper.

      @techreport{PMS-FB-2006-11,
              author = {Hans J\"urgen Ohlbach},
              title = {Periodic Temporal Notions as 'Tree Partitionings'},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-11},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-11}
      }
      

The FuTI--library is a collection of classes and methods for representing and manipulating fuzzy time intervals. Fuzzy time intervals are represented as polygons over integer coordinates. FuTI is an open source C++ library with many advances operations and highly optimised algorithms. Version 1.0 is now available from the URL https://www.pms.ifi.lmu.de/CTTN/FuTI.

      @inproceedings{PMS-FB-2006-10,
              author = {Hans J\"urgen Ohlbach},
              title = {Fuzzy Time Intervals - System Description of the FuTI-Library},
              booktitle = {Proceedings of 4th Workshop on Principles and Practice of Semantic Web Reasoning, Budva, Montenegro (10th--11th June 2006)},
              year = {2006},
              volume = {4187},
              series = {LNCS},
              pages = {257--261},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-10}
      }
      

Styling and formatting of XML documents for various target media is often specified with the Cascading Style Sheet (CSS) language. An appealing feature of CSS is that it specifies formatting instructions using rather simple guarded rules. A limitation of CSS is that it focuses on static formatting rules. As a consequence scripting languages such as ECMA Script are used in practice for dynamic adaptation of formatting. CSS-NG is a novel extension of CSS 3, the newest version of CSS, introducing just a few rules for a dynamic rendering and for markup visualization. This limited extension of CSS 3 turns out to make possible a rather advanced visualization of programs. This article (1) introduces into the extensions of CSS-NG with respect to CSS 3, (2) describes a proof-of-concept prototype implementation of CSS-NG, and (3) demonstrates CSS-NG on Xcerpt query programs.

      @inproceedings{PMS-FB-2006-9,
              author = {Fran\c{c}ois Bry and Christoph Wieser},
              title = {Web Queries with Style: Rendering Xcerpt Programs with CSS-NG},
              booktitle = {Proceedings of 4th Workshop on Principles and Practice of Semantic Web Reasoning, Budva, Montenegro (10th--11th June 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-9}
      }
      

This article proposes a framework to model and reason on what we call multi-calendar appointment scheduling problems. Multicalendar appointment scheduling problems such as planning a phone conference of three persons in France, Tunisia, and Japan refer to various temporal conditions, involving arbitrary calendric types such as months (Islamic months are defined differently from Gregorian months) possibly belonging to different calendars (e.g. the Gregorian calendar and the Islamic calendar). To solve such problems, we suggest a new class of Constraint Satisfaction Problems (CSPs); we call them Multi-Calendar CSPs. In this framework, the constraint variables are identified with finite, convex intervals in some calendric type and time constraints on such variables are expressed in terms of typed finite domain constraints. To solve time constraints which are defined on variables of different calendric types, a novel constraint, called calendar conversion constraint is proposed.

      @inproceedings{PMS-FB-2006-8,
              author = {Stephanie Spranger and Fran\c{c}ois Bry},
              title = {Multi-Calendar Appointment Scheduling: Calendar Modeling and Constraint Reasoning},
              booktitle = {Proceedings of 6th International Conference on the Practice and Theory of Automates Timetabling, Brno, Czech Republic (30th August--1st September 2006)},
              year = {2006},
              pages = {496--501},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-8}
      }
      

Temporal knowledge representation and reasoning is a major research field in Artificial Intelligence, in Database Systems, and in Web and Semantic Web research. The ability to model and process time and calendar data is essential for many applications like appointment scheduling, planning, Web services, temporal and active database systems, adaptive Web applications, and mobile computing applications. This article aims at three complementary goals. First, to provide with a general background in temporal data modeling and reasoning approaches. Second, to serve as an orientation guide for further specific reading. Third, to point to new application fields and research perspective on temporal knowledge representation and reasoning in the Web and Semantic Web.

      @techreport{PMS-FB-2006-7,
              author = {Stephanie Spranger and Fran\c{c}ois Bry},
              title = {Temporal Data Modeling and Reasoning for Information Systems},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-7},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-7}
      }
      

This articles discusses rule languages that are needed for a a full deployment of the SemanticWeb. First, it motivates the need for such languages. Then, it presents ten theses addressing (1) the rule and/or logic languages needed on the Web, (2) data and data processing, (3) semantics, and (4) engineering and rendering issues. Finally, it discusses two options that might be chosen in designing a Rule Interchange Format for the Web.

      @techreport{PMS-FB-2006-6,
              author = {Fran\c{c}ois Bry and Massimo Marchiori},
              title = {Towards a Rule Interchange Language for the Web},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-6},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-6}
      }
      

In this work we demonstrate a particular use of ontologies for visualising maps in a browser window. Geographic data are represented in the OWL data format that corresponds to an ontology of transporation networks which was designed in close relation to the concepts of the Geographic Data Format (GDF). These data are transformed into Scalable Vector Graphics (SVG). The transformation is specified symbolically as instances of a transformation ontology. This approach is extremely flexible and easily extendible to include all kinds of information in the generated maps. The basic implementation technique is to use classes and instances of ontologies in an intelligent way.

      @techreport{PMS-FB-2006-5,
              author = {Frank Ipfelkofer and Bernhard Lorenz and Hans J\"urgen Ohlbach},
              title = {Ontology Driven Visualisation of Maps with SVG -- An Example for Semantic Programming},
              institution = {Institute for Informatics, University of Munich},
              year = {2006},
              type = {Research Report},
              number = {PMS-FB-2006-5},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-5}
      }
      

Reactivity, the ability to detect and react to events, is an essential functionality in many information systems. In particular, Web systems such as online marketplaces, adaptive (e.g., recommender) systems, and Web services, react to events such as Web page updates or data posted to a server. This article investigates issues of relevance in designing high-level programming languages dedicated to reactivity on the Web. It presents twelve theses on features desirable for a language of reactive rules tuned to programming Web and Semantic Web applications.

      @inproceedings{PMS-FB-2006-4,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Twelve Theses on Reactive Rules for the Web},
              booktitle = {Proceedings of Workshop "Reactivity on the Web" at the International Conference on Extending Database Technology, Munich, Germany (31st March 2006)},
              year = {2006},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-4}
      }
      

Reactivity on the Web is an emerging research issue covering: updating data on the Web, exchanging information about events (such as executed updates) between Web sites, and reacting to combinations of such events. Reactivity plays an important role for upcoming Web systems such as online marketplaces, adaptive Web and Semantic Web systems, as well as Web services and Grids. This article introduces the paradigms upon which the high-level language XChange for programming reactive behaviour and distributed applications on the Web relies. Then, it briefly presents the main syntactical constructs of XChange and their declarative and operational semantics.

      @article{PMS-FB-2006-3,
              author = {Fran\c{c}ois Bry and Michael Eckert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Reactivity on the Web: Paradigms and Applications of the Language XChange},
              journal = {Journal of Web Engineering},
              year = {2006},
              volume = {5},
              number = {1},
              pages = {3--24},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-3}
      }
      

Reactivity, the ability to detect events and respond to them automatically through reactive programs, is a key requirement in many present-day information systems. Work on Web Services reflects the need for support of reactivity on a higher abstraction level than just message exchange by HTTP. This article presents the composite event query facilities of the reactive rule-based programming language XChange. Composite events are important in the dynamic world of the Web where applications, or Web Services, that have not been engineered together are composed and have to cooperate by exchanging event messages.

      @inproceedings{PMS-FB-2006-2,
              author = {Fran\c{c}ois Bry and Michael Eckert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Querying Composite Events for Reactivity on the Web},
              booktitle = {Proceedings of International Workshop on XML Research and Applications (XRA) 15 Jan 2006, in conjunction with Asia-Pacific Web Conference, Harbin, China (16th--18th January 2006)},
              year = {2006},
              volume = {3842},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-2}
      }
      

This paper presents a demonstration of Xcerpt and visXcerpt [PMS-FB-2003-6, PMS-FB-2003-2], a textual and a visual query language for both, standard Web as well as Semantic Web applications. Xcerpt and visXcerpt are based upon a few unconventional principles: (1) Xcerpt and visXcerpt are query languages tuned to querying all kind of Web and Semantic Web data, i.e. arbitrary XML documents, (2) Xcerpt and visXcerpt are capable of (simple) inferences as encountered with database views and Semantic Web reasoning, and (3) visXcerpt has been conceived as a mere rendering (using a slightly extended CSS) of the (textual) query language Xcerpt [PMS-FB-2004-7] (cf. http://xcerpt.org).

      @inproceedings{PMS-FB-2006-1,
              author = {Sacha Berger and Fran\c{c}ois Bry and Tim Furche},
              title = {Xcerpt and visXcerpt: Integrating Web Querying},
              booktitle = {Proceedings of Programming Language Technologies for XML, Charleston, South Carolina (14th January 2006)},
              year = {2006},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2006-1}
      }
      

This articles is a structured bibliography on theorem provers, approaches to theorem proving, and theorem proving applications inspired from Satchmo, the model generation theorem prover developed in the mid 80es of the 20th century at ECRC, the European Computer- Industry Research Centre. Note that the bibliography given in this article is not exhaustive.

      @techreport{PMS-FB-2005-45,
              author = {Fran\c{c}ois Bry and Rainer Manthey},
              title = {Variations on a Theme: A Bibliography on Approaches to Theorem Proving Inspired From Satchmo},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-45},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-45}
      }
      

Abstracts Collection of the Workshop and Dagstuhl Seminar 05371 "Principles and Practices of Semantic Web Reasoning (PPSWR 2005)".

      @inproceedings{PMS-FB-2005-44,
              author = {Fran\c{c}ois Bry and Fran\c{c}ois Fages and Massimo Marchiori and Hans J\"urgen Ohlbach (eds.)},
              title = {Abstracts Collection of the Workshop and Dagstuhl Seminar 05371 "Principles and Practices of Semantic Web Reasoning (PPSWR 2005)"},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, Dagstuhl Castle, Germany (11th--16th September 2005)},
              year = {2005},
              volume = {LNCS 3703},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-44}
      }
      

This articles discusses the logic, or logic-based, languages required for a full deployment of the Semantic Web. It presents ten theses addressing the kinds of logic languages needed, data and data processing, semantics, and engineering and rendering issues. The views reported about in this article have been presented at the W3C Workshop on Rule Languages for Interoperability (27-28 April 2005, Washington, D.C., USA, http://www.w3.org/2004/12/rules-ws/).

      @inproceedings{PMS-FB-2005-43,
              author = {Fran\c{c}ois Bry and Massimo Marchiori},
              title = {Ten Theses on Logic Languages for the Semantic Web},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, Dagstuhl Castle, Germany (11th--16th September 2005)},
              year = {2005},
              volume = {LNCS 3703},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-43}
      }
      

Due to the Semantic Web's decentralised and distributed management, contradictory information is and will remain frequent. However, classical reasoning systems fail to work properly in the presence of inconsistencies, because they implicitly or explicitly assume the ex contradictione quod libet (ECQL) principle stating that anything follows from contradictory premises. Paraconsistent reasoning challenges this ECQL principle. Stressing practical cases of reasoning on the Web, this position paper first argues that paraconsistent reasoning is likely to become a key issue for successful deployment of the Semantic Web. Then, it briefly introduces the main approaches to date to paraconsistent reasoning.

      @inproceedings{PMS-FB-2005-42,
              author = {Sebastian Schaffert and Fran\c{c}ois Bry and Philippe Besnard and Hendrik Decker and Stefan Decker and Carlos F. Enguix and Andreas Herzig},
              title = {Position Paper: Paraconsistent Reasoning for the Semantic Web},
              booktitle = {Uncertainty Reasoning for the Semantic Web, Proceedings of Workshop Uncertainty Reasoning for the semantic Web at the International Semantic Web, Galway, Ireland (7th November 2005)},
              year = {2005},
              pages = {104--105},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-42}
      }
      

This article discusses forms of reasoning (beyond ontology reasoning), and reasoning languages (beyond ontology languages), that are needed for a full deployment of the Semantic Web. We first outline a motivating application scenario, then discuss the logic languages needed on the Semantic Web and related issues. The views reported about in this article underly and have been developed within the EU research project REWERSE (REasoning on the WEb with Rules and SEmantics, cf. http://rewerse.net).

      @inproceedings{PMS-FB-2005-41,
              author = {Fran\c{c}ois Bry and Massimo Marchioni},
              title = {Reasoning on the Web: Beyond Ontology Languages and Reasoners},
              booktitle = {Proceedings of European Workshop on the Integration of Knowledge, Semantics and Digital Media Technology, London, U.K (30th November--1st December 2005)},
              year = {2005},
              organization = {The Institution of Electrical Engineers, IEE},
              pages = {317--321},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-41}
      }
      

This article introduces XChange, a rule-based reactive language for the (Semantic) Web. Stressing application scenarios, it first argues that high-level reactive languages are needed for both Web and Semantic Web applications. Then, it discusses technologies and paradigms relevant to high-level reactive languages for the (Semantic) Web.

      @inproceedings{PMS-FB-2005-40,
              author = {James Bailey and Fran\c{c}ois Bry and Michael Eckert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Flavours of XChange, a Rule-Based Reactive Language for the (Semantic) Web},
              booktitle = {Proceedings of International Conference on Rules and Rule Markup Languages for the Semantic Web, Galway, Ireland (10th--12th November 2005)},
              year = {2005},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-40}
      }
      

      @inproceedings{PMS-FB-2005-39,
              author = {Sacha Berger and Emmanuel Coquery and W{\l}odzimierz Drabent and Artur Wilk},
              title = {Descriptive Typing Rules for Xcerpt},
              booktitle = {Proceedings of Third Workshop on Principles and Practice of Semantic Web Reasoning, Dagstuhl, Germany (11th--16th September 2005)},
              year = {2005},
              organization = {REWERSE},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-39}
      }
      

      @inproceedings{PMS-FB-2005-38,
              author = {Tim Furche and Fran\c{c}ois Bry and Oliver Bolzer},
              title = {Marriages of Convenience: Triples and Graphs, RDF and XML},
              booktitle = {Proceedings of the Third International Workshop on Principles and Practice of Semantic Web Reasoning 2005, Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, Dagstuhl Castle, Germany (11th--16th September 2005)},
              year = {2005},
              volume = {LNCS 3703},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-38}
      }
      

This article introduces XChange, a rule-based reactive language for the Web. Stressing application scenarios, it first argues that high-level reactive languages are needed for bothWeb and SemanticWeb applications. Then, it discusses technologies and paradigms relevant to high-level reactive languages for the (Semantic) Web. Finally, it presents the Event-Condition-Action rules of XChange.

      @techreport{PMS-FB-2005-37,
              author = {James Bailey and Fran\c{c}ois Bry and Michael Eckert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Flavours of XChange, a Rule-Based Reactive Language for the (Semantic) Web},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-37},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-37}
      }
      

This article introduces a preliminary declarative semantics for a subset of the language Xcerpt (so-called grouping-stratifiable programs) in form of a classical (Tarski style) model theory, adapted to the specific requirements of Xcerpt s constructs (e.g. the various aspects of incompleteness in query terms, grouping constructs in rule heads, etc.). Most importantly, the model theory uses term simulation as a replacement for term equality to handle incomplete term specifications, and an extended notion of substitutions in order to properly convey the semantics of grouping constructs. Based upon this model theory, a fixpoint semantics is also described, leading to a first notion of forward chaining evaluation of Xcerpt programs.

      @techreport{PMS-FB-2005-36,
              author = {Sebastian Schaffert and Fran\c{c}ois Bry and Tim Furche},
              title = {Initial draft of a possible declarative semantics for the language},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-36},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-36}
      }
      

Reactivity on the Web is an emerging research issue covering: updating data on the Web, exchanging information about events (such as executed updates) between Web sites, and reacting to combinations of such events. Reactivity plays an important role for upcoming Web systems such as online marketplaces, adaptive, Semantic Web systems as well as Web services and Grids. After motivating the need for reactivity on the Web through an application scenario, this article introduces the paradigms upon which the high-level language XChange for programming reactive behaviour and distributed applications on the Web relies. Then, it brie y presents the main syntactical constructs of XChange. Finally, it sketches the implementation of a reactive Web-based application in XChange.

      @inproceedings{PMS-FB-2005-35,
              author = {Fran\c{c}ois Bry and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Reactivity on the Web: Paradigms and Applications of the Language XCHANGE},
              booktitle = {Proceedings of ACM Symposium on Applied Computing, Santa Fe, New Mexico, USA (13th--17th March 2005)},
              year = {2005},
              pages = {1645--1649},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-35}
      }
      

Reactivity, the ability to detect simple and composite events and respond in a timely manner, is an essential requirement in many present-day information systems. With the emergence of new, dynamic Web applications, reactivity on the Web is receiving increasing attention. Reactive Web-based systems need to detect and react not only to simple events but also to complex, real-life situations. This paper introduces XChange, a language for programming reactive behaviour on the Web, emphasising the querying of event data and detection of composite events.

      @techreport{PMS-FB-2005-34,
              author = {James Bailey and Fran\c{c}ois Bry and Michael Eckert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Reactivity on the Web: Event Queries in XChange},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-34},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-34}
      }
      

This document presents a structure of the field of the Semantic Web emerging from the information on Semantic Web-relevant courses collected in the REWERSE deliverable E-D1 and a list of introductory courses addressing a majority of topics identified in this structure. A brief description of each of the courses is given and the names of the REWERSE members who committed themselves to develop learning materials for inclusion into the VISWE repository (called VISWER). The materials are to be used at the 2005 REWERSE Summer School.

      @techreport{PMS-FB-2005-33,
              author = {Jan Maluszynski and J\"org Diederich and Norbert Eisinger and Artur Wilk},
              title = {REWERSE graduate courses: a preliminary list},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-33},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-33}
      }
      

This report presents a set of use cases for evolution and reactivity for data in the Web and Semantic Web. This set is organized around three different case study scenarios, each of them is related to one of the three different areas of application within Rewerse. Namely, the scenarios are: "The REWERSE Information System and Portal", closely related to the work of A3 Personalised Information Systems; "Organizing Travels", that may be related to the work of A1 Events, Time, and Locations; "Updates and evolution in bioinformatics data sources" related to the work of A2 -Towards a Bioinformatics Web.

      @techreport{PMS-FB-2005-32,
              author = {Jos\'{e} J\'{u}lio Alferes and Mikael Berndtsson and Fran\c{c}ois Bry and Michael Eckert and Nicola Henze and Wolfgang May and Paula-Lavinia P\u{a}tr\^anjan and Michael Schroeder},
              title = {Use-cases on evolution},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-32},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-32}
      }
      

The Semantic Web is an endeavour aiming at enhancing Web data with meta-data and data processing, as well as processing methods specifying the `meaning' of such data and allowing Web-based systems to take advantage of `intelligent' reasoning capabilities. The representation of the meaning of data essentially requires the development of a world model. Ontologies, for example, are logical descriptions of world models. In this paper we investigate what it means to develop a world model for `geospatial' data that can be used for semantic web applications. Different aspects are analysed and a proposal for a concrete architecture is developed. The architecture takes into account that geospatial data (road maps etc.) are usually owned by companies and only accessible through their interfaces. The article also argues that, to complement standard, general purpose, logic-based data modelling and reasoning methods, as e.g.\ offered by RDF and OWL and reasoners for these languages, location reasoning is best tackled using graphs for data modelling and well-established algorithms for reasoning. Hence, the article illustrates, for the practical case of location reasoning for providing guidance, the thesis that, on the Semantic Web, `theory reasoning' is a desirable complement to `standard reasoning'.

      @inproceedings{PMS-FB-2005-31,
              author = {Fran\c{c}ois Bry and Bernhard Lorenz and Hans J\"urgen Ohlbach and Mike Rosner},
              title = {A Geospatial World Model for the Semantic Web},
              booktitle = {Proceedings of Third Workshop on Principles and Practice of Semantic Web Reasoning, Dagstuhl, Germany (11th--16th September 2005)},
              year = {2005},
              organization = {INRIA},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-31}
      }
      

Accessing and querying geographical data in a uniform way has becomeeasier in recent years. Emerging standards like WFS turn the web into a geospatial web services enabled place. Mediation architectures like VirGIS overcome syntactical and semantical heterogeneity between several distributed sources. On mobile devices, however, this kind of solution is not suitable, due to limitations, mostly regarding bandwidth, computation power, and available storage space. The aim of this paper is to present a solution for providing powerful reasoning mechanisms accessible from mobile applications and involving data from several heterogeneous sources. By adapting contents to time and location, mobile web information systems can not only increase the value and suitability of the service itself, but can substantially reduce the amount of data delivered to users. Because many problems pertain to infrastructures and transportation i general and to way finding in particular, one cornerstone of the architecture is higher level reasoning on graph networks with the Multi-Paradigm Location Language MPLL. A mediation architecture is used as a ``graph provider'' in order to transfer the load of computation to the best suited component -- graph construction and transformation for example being heavy on resources. Reasoning in general can be conducted either near the ``source'' or near the end user, depending on the specific use case. The concepts underlying the proposal described in this paper are illustrated by a typical and concrete scenario for web applications.

      @techreport{PMS-FB-2005-30,
              author = {Fran\c{c}ois Bry and Francois-Marie Colonna and Bernhard Lorenz},
              title = {Multi-Paradigm Reasoning for Access to Heterogeneous GIS},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-30},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-30}
      }
      

The CTTN-system is a computer program which provides advanced processing or temporal notions. The basic data structures of the CTTN-system are time points, crisp and fuzzy time intervals, labelled partitionings of the time line, durations, and calendar systems. The labelled partitionings are used to model periodic temporal notions, quite regular ones like years, months etc., partially regular ones like timetables, but also very irregular ones like, for example, dates of a conference series. These data structures can be used in the temporal speci cation language GeTS (GeoTemporal Speci cations). GeTS is a functional specification and programming language with a number of built-in constructs for specifying customized temporal notions. CTTN is implemented as a Web server and as a C++ library. This paper gives a short overview over the current state of the system and its components.

      @inproceedings{PMS-FB-2005-29,
              author = {Hans J\"urgen Ohlbach},
              title = {Computational Treatment of Temporal Notions The CTTN-System},
              booktitle = {Proceedings of Third Workshop on Principles and Practice of Semantic Web Reasoning, Dagstuhl, Germany (11th--16th September 2005)},
              year = {2005},
              organization = {INRIA},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-29}
      }
      

This document describes the `Geo-Temporal' specification language GeTS. The objects which can be described and manipulated with this language are time points, crisp and fuzzy time intervals and labelled partitionings of the time axis. The partitionings are used to represent periodic temporal notions like months, semesters etc. GeTS is essentially a typed functional language with a few imperative constructs. GeTS can be used to specify and compute with many different kinds of temporal notions, from simple arithmetic operations on time points up to complex fuzzy relations between fuzzy time intervals. The syntax of GeTS together with an operational semantics is described. A parser, a compiler and an abstract machine for GeTS is implemented. The application programming interface for GeTS is documented in the appendix.

      @inproceedings{PMS-FB-2005-28,
              author = {Hans J\"urgen Ohlbach},
              title = {GeTS - A Specification Language for Geo-Temporal Notions},
              booktitle = {KI 2006: Advances in Artificial Intelligence, Proceedings of 29th Annual German Conference on AI, Bremen, Germany (14th--17th June 2006)},
              year = {2005},
              volume = {4314},
              series = {Lecture Notes in Artificial Intelligence},
              pages = {214--228},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-28}
      }
      

The key notion for modelling calendar systems and many other periodic temporal notion is the mathematical concept of a partitioning of the real numbers. A partitioning of R splits the time axis into a sequence of intervals. Basic time units like seconds, minutes, hours, days, weeks, months, years etc. can all be represented by partitionings of R with finite partitions. Besides the basic time units in calendar systems, there are a lot of other temporal notions which can be modelled as partitions: the seasons, the ecclesiastical calendars, financial years, semesters at universities, the sequence of sunrises and sunsets, the sequence of the tides, the sequence of school holidays etc. In this paper a formalization of periodic temporal notions by means of labelled partitionings of R is presented. The formalism is implemented as the C++ library PartLib (Partitioning Library). The interface to PartLib is presented in the appendix.

      @techreport{PMS-FB-2005-27,
              author = {Hans J\"urgen Ohlbach},
              title = {Modelling Periodic Temporal Notions by Labelled Partitionings of the Real Numbers - The PartLib Library},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-27},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-27}
      }
      

The FuTI-library is a collection of classes and methods for representing and manipulating fuzzy time intervals. The report consists of three parts. The mathematical theory is described in the first part. The concrete representation of fuzzy time intervals as polygons, together with the algorithms for operating on these polygons is presented in the second part. Finally, the third part contains a short description of the application interface. FuTI is an open source C++ library.

      @techreport{PMS-FB-2005-26,
              author = {Hans J\"urgen Ohlbach},
              title = {Fuzzy Time Intervals - The FuTI-Library},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-26},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-26}
      }
      

      @proceedings{PMS-FB-2005-25,
              title = {Reasoning Web, First International Summer School 2005},
              year = {2005},
              editor = {Norbert Eisinger and Jan Maluszynski},
              publisher = {Springer-Verlag},
              volume = {3564},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-25}
      }
      

Since reactivity and evolution are tightly connected, use cases containing both aspects were collected in a single document, instead of compiling them in separate documents.

      @techreport{PMS-FB-2005-24,
              author = {Jos\'{e} J\'{u}lio Alferes and Mikael Berndtsson and Fran\c{c}ois Bry and Michael Eckert and Nicola Henze and Wolfgang May and Paula-Lavinia P\u{a}tr\^anjan and Michael Schroeder},
              title = {Use-cases on reactivity},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-24},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-24}
      }
      

For determining requirements and constructs appropriate for a Web query language, or in fact any language, use cases are of essence. The W3C has published two sets of use cases for XML and RDF query languages. In this article, solutions for these use cases are presented using Xcerpt. a novel Web and Semantic Web query language that combines access to standard Web data such as XML documents with access to Semantic Web metadata such as RDF resource descriptions with reasoning abilities and rules familiar from logicprogramming. To the best knowledge of the authors, this is the first in depth study of how to solve use cases for accessing XML and RDF in a single language: Integrated access to data and metadata has been recognized by industry and academia as one of the key challenges in data processing for the next decade. This article is a contribution towards addressing this challenge by demonstrating along practical and recognized use cases the usefulness of reasoning abilities, rules, and semistructured query languages for accessing both data (XML) and metadata (RDF).

      @techreport{PMS-FB-2005-23,
              author = {Oliver Bolzer and Fran\c{c}ois Bry and Tim Furche and Sebastian Kraus and Sebastian Schaffert},
              title = {Development of Use Cases, Part I},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-23},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-23}
      }
      

Hyperlinks are an essential feature of the World Wide Web, highly responsible for its success. XLink improves on HTML's linking capabilities in several ways. In particular, links after XLink can be "out-of-line" (i.e., not defined at a link source) and collected in (possibly several) linkbases, which considerably ease building complex link structures. Regarding its architecture as a distributed and open system, the Web differs significantly from traditional hypermedia systems. Modeling of link structures and processing of linkbases under the Web's "open world linking" require rethinking the traditional approaches. This, unfortunately, has been rather neglected in the design of XLink. Adding a notion of "interface" to XLink, as suggested in this work, can considerably improve modeling of link structures. When a link structure is traversed, the relevant linkbase(s) might become ambiguous. We suggest three linkbase management modes governing the binding of a linkbase to a document to resolve this ambiguity.

      @inproceedings{PMS-FB-2005-22,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Processing Link Structures and Linkbases in the Web`s Open World Linking},
              booktitle = {Proceedings of Sixteenth ACM Conference on Hypertext and Hypermedia, Salzburg, Austria (6th--9th September 2005)},
              year = {2005},
              pages = {135--144},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-22}
      }
      

Abstract. Time and calendars play an important role in databases, on the Semantic Web, as well as in mobile computing. Temporal data and calendars require (specific) modeling and processing tools. CaTTS is a type language for calendar de nitions using which one can model and process temporal and calendric data. CaTTS is based on a "theory reasoning" approach for efficiency reasons. This article addresses type checking temporal and calendric data and constraints. A thesis underlying CaTTS is that types and type checking are as useful and desir- able with calendric data types as with other data types. Types enable (meaningful) annotation of data. Type checking enhances efficiency and consistency of programming and modeling languages like database and Web query languages.

      @techreport{PMS-FB-2005-21,
              author = {Fran\c{c}ois Bry and Frank-Andr\'{e} Rie{\ss} and Stephanie Spranger},
              title = {A Type Language for Calendars},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-21},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-21}
      }
      

Abstract. Time and calendars play an important role in databases, on the Semantic Web, as well as in mobile computing. Temporal data and calendars require (specific) modeling and processing tools. CaTTS is a type language for calendar de nitions using which one can model and process temporal and calendric data. CaTTS is based on a "theory reasoning" approach for efficiency reasons. This article addresses type checking temporal and calendric data and constraints. A thesis underlying CaTTS is that types and type checking are as useful and desir- able with calendric data types as with other data types. Types enable (meaningful) annotation of data. Type checking enhances effciency and consistency of programming and modeling languages like database and Web query languages.

      @techreport{PMS-FB-2005-20,
              author = {Fran\c{c}ois Bry and Frank-Andr\'{e} Rie{\ss} and Stephanie Spranger},
              title = {A Type Language for Calendars},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-20},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-20}
      }
      

This article introduces a programming language approach to modelling spatio-temporal data using calendars and topologies specified as types. Calendric and topologic data appearing in Web applications are most often rather complex, sometimes involving different calendars and/or topologies. The basic principle is to model spatio-temporal data by means of predicate subtyping. This principle is used to define calendric and topologic data types representing granularities as well as conversions between those data types. A thesis underlying this work is that calendars and topologies are more conveniently expressed with dedicated language constructs and that calendar and topology data are more effciently processed with dedicated reasoning methods than with general purpose "axiomatic reasoning" of e.g. ontology languages or theorem provers.

      @inproceedings{PMS-FB-2005-19,
              author = {Fran\c{c}ois Bry and Bernhard Lorenz and Stephanie Spranger},
              title = {Calendars and Topologies as Types - A Programming Language Approach to Modelling Mobile Applications},
              booktitle = {Proceedings of 9th International Conference on Knowledge-Based Intelligent Information & Engineering System, Melbourne, Australia (14th--16th September 2005)},
              year = {2005},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-19}
      }
      

Calendric and temporal data are omnipresent in countless Web and Semantic Web applications and Web services. Calendric and temporal data are probably more than any other data a subject to interpretation, in almost any case depending on some cultural, legal, professional, and/or locational context. On the current Web, calendric and temporal data can hardly be interpreted by computers. This article contributes to the Semantic Web, an endeavor aiming at enhancing the current Web with well-defined meaning and to enable computers to meaningfully process data. The contribution is a reasoner for calendric and temporal data. This reasoner is part of CaTTS, a type language for calendar definitions. The reasoner is based on a "theory reasoning" approach using constraint solving techniques. This reasoner complements general purpose "axiomatic reasoning" approaches for the Semantic Web as widely used with ontology languages like OWL or RDF.

      @techreport{PMS-FB-2005-18,
              author = {Fran\c{c}ois Bry and Frank-Andr\'{e} Rie{\ss} and Stephanie Spranger},
              title = {A Reasoner for Calendric and Temporal Data},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-18},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-18}
      }
      

Calendric and temporal data are omnipresent in countless Web and Semantic Web applications and Web services. Calendric and temporal data are probably more than any other data a subject to interpretation, in almost any case depending on some cultural, legal, professional, and/or locational context. On the current Web, calendric and temporal data can hardly be interpreted by computers. This article contributes to the Semantic Web, an endeavor aiming at enhancing the current Web with well-defined meaning and to enable computers to meaningfully process data. The contribution is a reasoner for calendric and temporal data. This reasoner is part of CaTTS, a type language for calendar definitions. The reasoner is based on a "theory reasoning" approach using constraint solving techniques. This reasoner complements general purpose "axiomatic reasoning" approaches for the Semantic Web as widely used with ontology languages like OWL or RDF.

      @techreport{PMS-FB-2005-17,
              author = {Fran\c{c}ois Bry and Frank-Andr\'{e} Rie{\ss} and Stephanie Spranger},
              title = {A Reasoner for Calendric and Temporal Data},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-17},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-17}
      }
      

Query and transformation languages such as XPath, XQuery and XSLT have evolved to standard development tools for Web applications. Arguably those languages are not fully suited for Semantic Web applications. The query and transformation languages Xcerpt and visXcerpt have been conceived with both standard Web and Semantic Web applications in mind. They are twin languages both based on the same paradigms and principles. Xcerpt realizes these paradigms and principles textually, visXcerpt visually. A mixed standardWeb and SemanticWeb application scenario implemented in Xcerpt and visXcerpt is presented. Xcerpt and visXcerpt are ongoing research projects; prototypic implementations of the languages are available.

      @inproceedings{PMS-FB-2005-16,
              author = {Sacha Berger and Fran\c{c}ois Bry and Oliver Bolzer and Tim Furche and Sebastian Schaffert and Christoph Wieser},
              title = {Querying the standard and Semantic Web using Xcerpt and visXcerpt},
              booktitle = {Proceedings of European Semantic Web Conference, Heraklion, Crete, Greece (29th May--1st June 2005)},
              year = {2005},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-16}
      }
      

Ontologies, which are structured, hierarchical vocabularies, are widely used in molecular biology to annotate sequence and structure data. One such ontology, the GeneOntology, contains some 18000 terms on biological processes, molecular function, and cellular components. GeneOntology is available as flat file, in web formats such as XML and RDF, and as database. Using these formats we compare three different reasoners to query the GeneOntology. Prolog is the classical logic programming approach to reason over the ontology, Prova is a rule-based Java scripting language, and Xcerpt a query language for XML and RDF. We conclude by discussing the strengths and weaknesses of the three approaches.

      @inproceedings{PMS-FB-2005-15,
              author = {Andreas Doms and Tim Furche and Albert Burger and Michael Schroeder},
              title = {How to Query the GeneOntology},
              booktitle = {Proceedings of Symposium on Knowledge Representation in Bioinformatics, Espoo, Finland (17th June 2005)},
              year = {2005},
              pages = {47--50},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-15}
      }
      

A number of techniques have been developed to facilitate powerful data retrieval on the Web and Semantic Web. Three categories of Web query languages can be distinguished, according to the format of the data they can retrieve: XML, RDF and Topic Maps. This article introduces the spectrum of languages falling into these categories and summarises their salient aspects. The languages are introduced using common sample data and query types. Key aspects of the query languages considered are stressed in a conclusion.

      @incollection{PMS-FB-2005-14,
              author = {James Bailey and Fran\c{c}ois Bry and Tim Furche and Sebastian Schaffert},
              title = {Web and Semantic Web Query Languages: A Survey},
              booktitle = {Reasoning Web, First International Summer School 2005},
              publisher = {Springer-Verlag},
              year = {2005},
              volume = {3564},
              type = {{ unknown }},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-14}
      }
      

The integral processing of data and metadata is starting to get recognized as a central challenge for the next decade (e.g. in Pat Selinger s ICDE 2005 Keynote) not only as part of realizing the Semantic Web vision, but also on a smaller scale as part of the next generation of desktop data management (cf. Apple s Spotlight and Microsoft s WinFS). In this article, we focus on metadata represented in the W3C s RDF formalism. We illustrate first steps towards integrating access to RDF metadata and access to standard Web data in XML format. For this, two XML views over RDF data are expressed in the query language Xcerpt and discussed. These views illustrate two di erent approaches for integrating RDF metadata processing and current data processing techniques.

      @inproceedings{PMS-FB-2005-13,
              author = {Tim Furche and Fran\c{c}ois Bry and Oliver Bolzer},
              title = {XML Perspectives on RDF Querying: Towards integrated Access to Data and Metadata on the Web},
              booktitle = {Proceedings of 17. Workshop über Grundlagen von Datenbanken, W\"orlitz, Germany (17th--20th May 2005)},
              year = {2005},
              organization = {GI},
              pages = {43--47},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-13}
      }
      

This article reports on a research project investigating the following two complementary issues: (1) improving how the structure of XML and HTML can be specified, (2) using structure specification (of XML and HTML documents) for static type checking of Web (and Semantic Web) query programs. The first step towards this goal is to provide a schema language like DTD, XML Schema or Relax-NG with better support of graph structured data.

      @inproceedings{PMS-FB-2005-12,
              author = {Sacha Berger and Fran\c{c}ois Bry},
              title = {Towards static type checking of Web query language},
              booktitle = {Proceedings of 17. Workshop über Grundlagen von Datenbanken, W\"orlitz, Germany (17th--20th May 2005)},
              year = {2005},
              organization = {GI},
              pages = {28--32},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-12}
      }
      

Current XML differencing applications usually try to find a minimal sequence of edit operations that transform one XML document to another XML docum ent (the so-called "edit script"). In our conviction, this approach often produces increments that are unintuitive for human readers and do not reflect the actual changes. We therefore propose in this article a different approach trying to maximise the retained structure instead of minimising the edit sequence. Structure is thereby not limited to the usual tree structure of XML - any kind of structural relations can be considered (like parent-child, ancestor-descendant, sibling, document order). In our opinion, this approach is very flexible and able to adapt to the user's requirements. It produces more readable results while still retaining a reasonably small edit sequence.

      @inproceedings{PMS-FB-2005-11,
              author = {Erich Schubert and Sebastian Schaffert and Fran\c{c}ois Bry},
              title = {Structure-Preserving Difference Search for XML Documents},
              booktitle = {Proceedings of Extreme Markup Languages 2005, Montr\'{e}al, Qu\'{e}bec, Canada (1st--5th August 2005)},
              year = {2005},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-11}
      }
      

This article presents an approach to context-aware services for "smart buildings" based on Web and Semantic Web techniques. The services striven for are first described, then their realization using Web and Semantic Web services is explained. Finally, advantages of the approach are stressed.

      @inproceedings{PMS-FB-2005-10,
              author = {Fran\c{c}ois Bry and Takashi Hattori and Kaoru Hiramatsu and Takeshi Okadome and Christoph Wieser and Tatsumi Yamada},
              title = {Context Modeling in OWL for Smart Building Services},
              booktitle = {Proceedings of 17. Workshop über Grundlagen von Datenbanken, W\"orlitz, Germany (17th--20th May 2005)},
              year = {2005},
              organization = {GI},
              pages = {38--42},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-10}
      }
      

Hyperlinks are an essential feature of the World Wide Web, highly responsible for its success. XLink improves on HTML's linking capabilities in several ways. In particular, links after XLink can be "out-of-line" (i.e., not defined at a link source) and collected in (possibly several) linkbases, which considerably ease building complex link structures. Modeling of link structures and processing of linkbases under the Web's "open world linking" are aspects neglected by XLink. Adding a notion of "interface" to XLink, as suggested in this work, considerably improves modeling of link structures. When a link structure is traversed, the relevant linkbase(s) might become ambiguous. We suggest three linkbase management modes governing the binding of a linkbase to a document to resolve this ambiguity.

      @inproceedings{PMS-FB-2005-9,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Processing Link Structures and Linkbases on the Web},
              booktitle = {Proceedings of 14th International World Wide Web Conference, Chiba, Japan (10th--14th May 2005)},
              year = {2005},
              organization = {W3C},
              pages = {1030--1031},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-9}
      }
      

Reactivity on the Web is an emerging issue. The capability to automatically react to events (such as updates to Web resources) is essential for both Web services and Semantic Web systems. Such systems need to have the capability to detect and react to complex, real life situations. This presentation gives flavours of the high-level language XChange, for programming reactive behaviour on the Web.

      @inproceedings{PMS-FB-2005-8,
              author = {James Bailey and Fran\c{c}ois Bry and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Composite Event Queries for Reactivity on the Web},
              booktitle = {Proceedings of 14th International World Wide Web Conference, Chiba, Japan (10th--14th May 2005)},
              year = {2005},
              organization = {W3C},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-8}
      }
      

This articles discusses the logic, or logic-based, languages required for a full deployment of the Semantic Web. It presents ten theses addressing (1) the kinds of logic languages needed, (2) data and data processing, (3) semantics, and (4) engineering and rendering issues.

      @inproceedings{PMS-FB-2005-7,
              author = {Fran\c{c}ois Bry and Massimo Marchiori},
              title = {Ten Theses on Logic Languages for the Semantic Web},
              booktitle = {Proceedings of W3C Workshop on Rule Languages for Interoperability, Washington D.C., USA (27th--28th April 2005)},
              year = {2005},
              organization = {W3C},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-7}
      }
      

Personalisierte Software zielt darauf ab, implementierte Funktionalität aufgrund der Anforderungen der individuellen Endanwender zu optimieren: Im Idealfall sollte personalisierte Software den Anwendern als direkt für ihre persönlichen Bedürfnisse und Anforderungen entwickelt erscheinen. Der Endanwender rückt damit nicht nur beim Entwurf der Software in den Mittelpunkt, sondern insbesondere beim Laufzeitverhalten: Erst die Berücksichtigung der zur Laufzeit aktuellen, möglicherweise komplexen Anforderungen und Bedürfnisse eines Benutzers bestimmen das letztendlicheVerhalten der Software.

      @techreport{PMS-FB-2005-6,
              author = {Fran\c{c}ois Bry and Nicola Henze},
              title = {Personalisierung},
              institution = {Institute for Informatics, University of Munich},
              year = {2005},
              type = {Research Report},
              number = {PMS-FB-2005-6, 3},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-6}
      }
      

Data referring to cultural calendars such as the widespread Gregorian dates but also dates after the Chinese, Hebrew, or Islamic calendars as well as data referring to professional calendars like fiscal years or teaching terms are omnipresent on the Web. Formalisms such as XML Schema have acknowledged this by offering a rather extensive set of Gregorian dates and times as basic data types. This article introduces into CaTTS, the Calendar and Time Type System. CaTTS goes far beyond predefined date and time types after the Gregorian calendar as supported by XML Schema. CaTTS first gives rise to declaratively specify more or less complex cultural or professional calendars including specificities such as leap seconds, leap years, and time zones. CaTTS further offers a tool for the static type checking (of data typed after calendar(s) defined in CaTTS). CaTTS finally offers a language for declaratively expressing and a solver for efficiently solving temporal constraints (referring to calendar(s) expressed in CaTTS). CaTTS complements data modeling and reasoning methods designed for generic Semantic Web applications such as RDF or OWL with methods specific to the particular application domain of calendars and time.

      @inproceedings{PMS-FB-2005-5,
              author = {Fran\c{c}ois Bry and Frank-Andr\'{e} Rie{\ss} and Stephanie Spranger},
              title = {CaTTS: Calendar Types and Constraints for Web Applications},
              booktitle = {Proceedings of 14th International World Wide Web Conference, Chiba, Japan (10th--14th May 2005)},
              year = {2005},
              organization = {W3C},
              pages = {702--711},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-5}
      }
      

Calendar data such as dates are probably more than any other data domain a subject to interpretation. Calendars are human abstractions of the physical flow of time predominately depending on culture, especially religion and history. They allow for measuring time in di erent units like day, week, working day, and also teaching term. The vision of the Semantic Web is to enrich the current Web with well-defined meanings and to enable computers to meaningfully process such data. This paper contributes to the Semantic Web vision with a generic modeling language called CaTTS. Using CaTTS, one can easily define arbitrary calendars. The language provides with CaTTS-TDL, a tool to define calendars and CaTTSFDL, a tool to define calendar data, in particular dates to give calendar data well-defined meanings. Furthermore, CaTTS provides a way to enable computers to meaningfully process the calendar data. Thus, CaTTS brings important cultural artefacts, the calendars, on the (Semantic) Web.

      @inproceedings{PMS-FB-2005-4,
              author = {Fran\c{c}ois Bry and Jutta Hau{\ss}er and Frank-Andr\'{e} Rie{\ss} and Stephanie Spranger},
              title = {Cultural Calendars for Programming and Querying},
              booktitle = {Proceedings of 1st Forum on the Promotion of European and Japanese Culture in Cyber-Societies and Virtual Reality, Laval, France (18th--19th April 2005)},
              year = {2005},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-4}
      }
      

A decade of experience with research proposals as well as standardized query languages for the conventional Web and the recent emergence of query languages for the Semantic Web call for a reconsideration of design principles for Web and Semantic Web query languages. This article first argues that a new generation of versatile Web query languages is needed for solving the challenges posed by the changing Web: We call versatile those query languages able to cope with both Web and Semantic Web data expressed in any (Web or Semantic Web) markup language. This article further suggests that (well-known) referential transparency and (novel) answer-closedness are essential features of versatile query languages. Indeed, they allow queries to be considered like forms and answers like form-fillings in the spirit of the "query-by-example" paradigm. This article finally suggests that the decentralized and heterogeneous nature of the Web requires incomplete data specifications (or "incomplete queries") and incomplete data selections (or "incomplete answers"): the form-like query can be specified without precise knowledge of the queried data and answers can be restricted to contain only an excerpt of the queried data.

      @article{PMS-FB-2005-3,
              author = {Fran\c{c}ois Bry and Tim Furche and Liviu Badea and Christoph Koch and Sebastian Schaffert and Sacha Berger},
              title = {Querying the Web Reconsidered: Design Principles for Versatile Web Query Languages},
              journal = {Journal of Semantic Web and Information Systems (IJSWIS)},
              year = {2005},
              volume = {1},
              number = {2},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-3}
      }
      

Reactivity on the Web is an emerging issue. It is essential for upcoming Web systems such as online market-places,adaptive, Semantic Web systems as well as Web servicesadaptiv, and Grids. This article first introduces the paradigms upon which the high-level language XChange for programming reactive behaviour and distributed applications on the Web relies. Then, it briefly presents the main syntactical constructs of XChange. Finally, it sketches the implementation in XChange of a reactive Web-based application.

      @inproceedings{PMS-FB-2005-2,
              author = {Fran\c{c}ois Bry and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Reactivity on the Web: Paradigms and Applications of the Language XChange},
              booktitle = {Proceedings of 20th Annual ACM Symposium on Applied Computing, Santa Fe (New Mexico), USA (13th--17th March 2005)},
              year = {2005},
              organization = {ACM},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-2}
      }
      

Data streams are an emerging technology for data dissemination in cases where the data throughput or size make it unfeasible to rely on the conventional approach based on storing the data before processing it. Areas where data streams are applied include monitoring of scientific data (astronomy, meteorology), control data (traffic, logistics, networks), and financial data (bank transactions). SPEX evaluates XPath queries against XML data streams. SPEX is built upon formal frameworks for (1) rewriting XPath queries into equivalent XPath queries without reverse axes and (2) correct query evaluation with polynomial complexity using networks of pushdown transducers.

      @inproceedings{PMS-FB-2005-1,
              author = {Fran\c{c}ois Bry and Fatih Coşkun and Serap Durmaz and Tim Furche and Dan Olteanu and Markus Spannagel},
              title = {The XML Stream Query Processor SPEX},
              booktitle = {Proceedings of 21st International Conference on Data Engineering, Tokyo, Japan (5th--8th April 2005)},
              year = {2005},
              organization = {IEEE},
              pages = {1120--1121},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2005-1}
      }
      

      @inproceedings{PMS-FB-2004-37,
              author = {Michael Marte},
              title = {Towards Constraint-Based School Timetabling},
              booktitle = {Proceedings of the Workshop on Modelling and Solving Problems with Constraints, Proceedings of 16th European Conference on Artificial Intelligence, Valencia, Spain (22nd--27th August 2004)},
              year = {2004},
              pages = {140--156},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-37}
      }
      

This deliverable contains a detailed description of the bottom layers of the WebCal system for representing and manipulating `geotemporal' information. The basic components are the FuTIRe library for representing fuzzy temporal intervals, the PartLib library for representing periodic temporal notions, and the mixed function layer, which deals with operations involving temporal intervals and periodic temporal notions. A first approach for representing named entities is described in the last chapter of this deliverable. These ideas are the basis for a knowledge representation system with, so far, 2000 entries of named entities.

      @techreport{PMS-FB-2004-36,
              author = {Hans J\"urgen Ohlbach and Klaus Schulz and Felix Weigel},
              title = {Geotemporal Reasoning: Basic Theory},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-36},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-36}
      }
      

      @inproceedings{PMS-FB-2004-35,
              author = {},
              title = {Principles and Practice of Semantic Web Reasoning},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, St. Malo, France (6th--10th September 2004)},
              year = {2004},
              editor = {Hans J\"urgen Ohlbach and Sebastian Schaffert},
              volume = {3208},
              organization = {REWERSE},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-35}
      }
      

      @inproceedings{PMS-FB-2004-34,
              author = {Hans J\"urgen Ohlbach},
              title = {Calendrical calculations with time partitionings and fuzzy time intervals},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, St. Malo, France (6th--10th September 2004)},
              year = {2004},
              volume = {3208},
              organization = {REWERSE},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-34}
      }
      

This paper serves two purposes. The first purpose is to introduce a new approach for defining point-interval and interval-interval relations for fuzzy time intervals. The basic idea for the interval-interval relations is to extend corresponding point-interval relations to interval-interval relations by averaging (integrating) the point-interval relation over the second interval. The new approach is compared with an existing approach by Nagyp al and Motik. The second purpose is to show how these relations can be easily de ned with the GeTS language (GeTS stands for GeoTemporal Specifications). This is a typed functional language with a large number of built{in data types and functions for manipulating temporal notions. The definitions of the point-interval and interval-interval relations are therefore given directly in the GeTS language. This report is an extended version of a paper presented at TIME 04.

      @inproceedings{PMS-FB-2004-33,
              author = {Hans J\"urgen Ohlbach},
              title = {Relations between fuzzy time intervals},
              booktitle = {Proceedings of 11th International Symposium on TEMPORAL REPRESENTATION AND REASONING, Tatihoui, Normandie, France (1st--3rd July 2004)},
              year = {2004},
              organization = {greyc},
              pages = {44--51},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-33}
      }
      

      @inproceedings{PMS-FB-2004-32,
              author = {Hans J\"urgen Ohlbach},
              title = {The role of labelled partitionings for modelling periodic temporal notions},
              booktitle = {Proceedings of 11th International Symposium on TEMPORAL REPRESENTATION AND REASONING, Tatihoui, Normandie, France (1st--3rd July 2004)},
              year = {2004},
              organization = {greyc},
              pages = {60--63},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-32}
      }
      

This document describes Reasoning Web 2005, the first REWERSE Summer School. The summer school proceedings [Maluszynski and Eisinger, 2005] published in the Lecture Notes in Computer Science series by Springer-Verlag, is an appendix to this document and forms an essential part of it.

      @techreport{PMS-FB-2004-31,
              author = {Norbert Eisinger and Jan Maluszynski},
              title = {Spring or Summer School I},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-31},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-31}
      }
      

A widely acknowledged obstacle for realizing the vision of the Semantic Web is the inability of many current Semantic Web approaches to cope with data available in such diverging representation formalisms as XML, RDF, or Topic Maps. A common query language is the first step to allow transparent access to data in any of these formats. To further the understanding of the requirements and approaches proposed for query languages in the conventional as well as the Semantic Web, this report surveys a large number of query languages for accessing XML, RDF, or Topic Maps. This is the first systematic survey to consider query languages from all these areas. From the detailed survey of these query languages, a common classification scheme is derived that is useful for understanding and di erentiating languages within and among all three areas.

      @techreport{PMS-FB-2004-30,
              author = {Tim Furche and Fran\c{c}ois Bry and Sebastian Schaffert and Renzo Orsini and Ian Horrocks and Michael Krauss and Oliver Bolzer},
              title = {Survey over Existing Query and Transformation Languages},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-30},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-30}
      }
      

This report starts by, in Chapter 1, outlining aspects of querying and updating resources on the Web and on the Semantic Web, including the development of query and update languages to be carried out within the Rewerse project. From this outline, it becomes clear that several existing research areas and topics are of interest for this work in REWERSE. In the remainder of this report we further present state of the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs; in Chapter 4 event-condition-action rules, both in the context of active database systems and in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks.

      @techreport{PMS-FB-2004-29,
              author = {Jos\'{e} J\'{u}lio Alferes and James Bailey and Mikael Berndtsson and Fran\c{c}ois Bry and Jens Dietrich and Alexander Kozlenkov and Wolfgang May and Paula-Lavinia P\u{a}tr\^anjan and Alexandre Pinto and Michael Schroeder and Gerd Wagner},
              title = {State-of-the-art on evolution and reactivity},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-29},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-29}
      }
      

This report identifies those design principles for a (possibly new) query and transformation language for the Web supporting inference that are considered essential. Based upon these design principles an initial strawman is selected. Scenarios for querying the Semantic Web illustrate the design principles and their reflection in the initial strawman, i.e., a first draft of the query language to be designed and implemented by the REWERSE working group I4.

      @techreport{PMS-FB-2004-28,
              author = {Fran\c{c}ois Bry and Tim Furche and Liviu Badea and Christoph Koch and Sebastian Schaffert and Sacha Berger},
              title = {Identification of Design Principles},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-28},
              note = {REWERSE Deliverable},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-28}
      }
      

      @article{PMS-FB-2004-27,
              author = {Grigoris Antoniou and Matteo Baldoni and Cristina Baroglio and Robert Baumgartner and Fran\c{c}ois Bry and Thomas Eiter and Nicola Henze and Marcus Herzog and Wolfgang May and Viviana Patti and Roman Schindlauer and Hans Tompits and Sebastian Schaffert},
              title = {Reasoning Methods for Personalization on the Semantic Web},
              journal = {Annals of Mathematics, Computing & Teleinformatics},
              year = {2004},
              volume = {2},
              number = {1},
              pages = {1--24},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-27}
      }
      

Reactivity on the Web is an emerging issue. The capability to automatically react to events (such as updates to Web resources) is essential for both Web services and Semantic Web systems. Such systems need to have the capability to detect and react to complex, real life situations. This paper introduces the high-level language XChange, for programming reactive behaviour on the Web, emphasising the capability of the language to express complex situations that occur on the Web by means of composite event queries.

      @inproceedings{PMS-FB-2004-26,
              author = {James Bailey and Fran\c{c}ois Bry and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Composite Event Queries for Reactivity on the Web},
              booktitle = {Proceedings of 14th International World Wide Web Conference, Chiba, Japan (11th--14th May 2005)},
              year = {2004},
              organization = {W3C},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-26}
      }
      

Hypertext links are an essential feature of the World Wide Web. Undoubtedly, much of the Web's success is due to HTML's linking capability. XML links, as specified in the XLink recommendation, improve on HTML's links in several ways. In particular, links after XLink can be "out-of-line" (i.e. not defined at a link source) and collected in (possibly several) linkbases. Linkbases considerably ease modeling complex link structures as encountered in context-adaptive systems (e.g. teaching systems), versatile information systems (e.g. eCommerce catalogs), and Web interfaces to systems of all kinds (e.g. eGovernment or banking interfaces). This article is devoted to two neglected aspects of XML links: the modeling of link structures and the processing of linkbases. It first shows how the modeling of link structures can be considerably improved by adding a notion of "interface" to XLink. Then, it shows that the relevant linkbase(s) might become ambiguous as a link structure is traversed. Three complementary modes for the binding of a linkbase to document(s) are proposed -- "transient", "permanent", and "temporary" -- as well as an algorithm for processing these bindings under the "open world linking" of the Web. Three usage scenarios are presented to demonstrate that with the approach proposed in this article the relevant linkbases are never ambiguous and the variety of behaviors required by Web applications can nicely be achieved. Finally, the relevance of XLink and the proposed linking modes to the Semantic Web is discussed.

      @techreport{PMS-FB-2004-25,
              author = {Fran\c{c}ois Bry and Michael Eckert},
              title = {Processing Link Structures and Linkbases on the Web and its Relevance to the Semantic Web},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-25},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-25}
      }
      

Data referring to cultural calendars such as the widespread Gregorian dates but also dates after the Chinese, Hebrew, or Islamic calendars as well as data referring to professional calendars like scal years or teaching terms are omnipresent on the Web. Formalisms such as XML Schema have acknowledged this by o ering a rather extensive set of Gregorian dates and times as basic data types. This article introduces into CaTTS, the Calendar and Time Type System. CaTTS goes far beyond prede ned date and time types after the Gregorian calendar as supported by XML Schema. CaTTS first gives rise to declaratively specify more or less complex cultural or professional calendars including special cities such as leap seconds, leap years, and time zones. CaTTS further as leap seconds, leap years, and time zones. CaTTS further offers a tool for the static type checking (of data typed after calendar(s) defined in CaTTS). CaTTS finally offers a language for declaratively expressing and a solver for efficiently solving temporal constraints (referring to calendar(s) expressed in CaTTS). CaTTS complements data modeling and reasoning methods designed for generic Semantic Web applications such as RDF or OWL with methods specific to the particular application domain of calendars and time.

      @inproceedings{PMS-FB-2004-24,
              author = {Fran\c{c}ois Bry and Frank-Andr\'{e} Rie{\ss} and Stephanie Spranger},
              title = {CaTTS: Calendar Types and Constraints for Web Applications},
              booktitle = {Proceedings of 14th International World Wide Web Conference, Chiba, Japan (11th--14th May 2005)},
              year = {2004},
              organization = {W3C},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-24}
      }
      

Query and transformation languages such as XPath, XQuery and XSLT have evolved to standard development tools for Web applications. Arguably those languages are not fully suited for Semantic Web applications. The query and transformation languages Xcerpt and visXcerpt have been conceived with both standard Web and Semantic Web applications in mind. They are twin languages both based on the same paradigms and principles. Xcerpt realizes these paradigms and principles textually, visXcerpt visually. A mixed standard Web and Semantic Web application scenario implemented in Xcerpt and visXcerpt is presented. Xcerpt and visXcerpt are ongoing research projects; prototypic implementations of the languages are available.

      @inproceedings{PMS-FB-2004-23,
              author = {Sacha Berger and Fran\c{c}ois Bry and Oliver Bolzer and Tim Furche and Sebastian Schaffert and Christoph Wieser},
              title = {Xcerpt and visXcerpt: Twin Query Languages for the Semantic Web},
              booktitle = {Proceedings of 3rd International Semantic Web Conference, Hiroshima, Japan (7th--11th November 2004)},
              year = {2004},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-23}
      }
      

"Grid-Computing", ein Mitte der 90er Jahre eingeführter Begriff [2,1], bezeichnet eine Architektur für verteilte Systeme, die auf dem World Wide Web aufbaut und die Web-Vision erweitert. Mit dem Grid-Computing werden die Ressourcen einer Gemeinschaft, einer sogenannten virtuellen Organisation (siehe unten), integriert. Die Hoffnung ist, dass hierdurch rechen- und/oder datenintensiven Aufgaben, die eine einzelne Organisation nicht lösen kann, handhabbar werden. Ein Grid bezeichnet eine nach dem Grid-Computing-Ansatz aufgebaute Rechner-, Netzwerk- und Software-Infrastruktur zur Teilung von Ressourcen mit dem Ziel, die Aufgaben einer virtuellen Organisation zu erledigen. Zu Beginn war die Möglichkeit, ungenutzte CPU-Ressourcen an anderen Stellen für die eigenen Aufgaben einzusetzen, die wesentlich treibende Kraft für erste Experimente. Internet-Computing-Projekte wie SETI@Home, distributed.net u.a., bei denen die unbenutzten Rechenzyklen von weltweit verteilten privaten PCs verwendet werden, illustrieren das Potential des Grid-Computing. Die heutigen Grid-Konzepte und die ersten -Prototypen gehen weit über diese Anfänge hinaus. Sie versprechen die transparente Bereitstellung von Diensten unabhängig von der räumlichen Nähe. Es wird erwartet, dass das Grid-Computing die Nutzung von Rechnern und Rechnernetzen so grundlegend verändern wird, wie das Web den Datenaustausch bereits verändert hat.

      @techreport{PMS-FB-2004-22,
              author = {Fran\c{c}ois Bry and Wolfgang E. Nagel and Michael Schroeder},
              title = {Grid-Computing},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-22, 6},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-22}
      }
      

      @inproceedings{PMS-FB-2004-21,
              author = {Rolf Backofen and Mike Badea and Pedro Barahona and Liviu Badea and Fran\c{c}ois Bry and Gihan Dawelbait and Andreas Doms and Fran\c{c}ois Fages and Carole Goble and Andreas Henschel and Anca Hotaran and Bingding Huang and Ludwig Krippahl and Patrick Lambrix and Werner Nutt and Michael Schroeder and Sylvain Soliman and Sebastian Will},
              title = {Poster: Towards a semantic web for bioinformatics},
              booktitle = {Proceedings of Bioinformatics 2004, Link\"oping, Sweden (3rd--6th June 2004)},
              year = {2004},
              organization = {SocBIN - Society for Bioinformatics in the Nordic countries},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-21}
      }
      

"For the semantic web to function, computers must have access to [...] sets of inference rules that they conduct automated reasoning." Tim Berners-Lee, James Hendle, and Ora Lassila. The Semantic Web, Scientific American, May 2001. REWERSE is a research Network of Excellence on "Reasoning on the Web" which is funded by the European Commission and Switzerland within the Sixth Framework Programme (FP6) under contract number 506779. REWERSE is funded as part of the IST strategic objective "Semantic-based knowledge systems". REWERSE started on 1st March 2004 and will run for four years. The EC and Switzerland will support REWERSE with more than 5 million Euro.

      @article{PMS-FB-2004-20,
              author = {Fran\c{c}ois Bry and Uta Schwertel},
              title = {REWERSE - Reasoning on the Web},
              journal = {AgentLink News},
              year = {2004},
              number = {15},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-20}
      }
      

Reasoning on the Web is gaining in importance because of emerging Web applications such as context-adaptive Web systems (e.g. eLearning, recommender, personalised (multi-)media, and mobile information systems), Web service retrieval and composition, and Semantic Web applications of all kinds. A central issue is combining automated reasoning methods with Web languages, especially with Web query, schema, and update languages. This article reports on prototypes of various kinds combining different forms of reasoning with Web languages. The languages presented here have been conceived for both, conventional Web and Semantic Web data, assuming that future Web applications will require to freely combine data of both kinds.

      @inproceedings{PMS-FB-2004-19,
              author = {Sacha Berger and Fran\c{c}ois Bry and Bernhard Lorenz and Hans J\"urgen Ohlbach and Paula-Lavinia P\u{a}tr\^anjan and Sebastian Schaffert and Uta Schwertel and Stephanie Spranger},
              title = {Reasoning on the Web: Language Prototypes and Perspectives},
              booktitle = {Proceedings of European Workshop on the Integration of Knowledge, Semantics and Digital Media Technology, London, U.K (25th--26th November 2004)},
              year = {2004},
              organization = {The Institution of Electrical Engineers, IEE},
              pages = {157--164},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-19}
      }
      

      @proceedings{PMS-FB-2004-18,
              title = {Principles and Practice of Semantic Web Reasoning (PPSWR04)},
              year = {2004},
              editor = {Hans J\"urgen Ohlbach and Sebastian Schaffert},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-18}
      }
      

This paper presents a demonstration of visXcerpt, a visual query language for both, standard Web as well as Semantic Web applications.

      @inproceedings{PMS-FB-2004-17,
              author = {Sacha Berger and Fran\c{c}ois Bry and Christoph Wieser},
              title = {Visual Querying for the Semantic Web},
              booktitle = {Proceedings of 23rd International Conference on Conceptual Modeling, Shanghai, China (8th--12th November 2004)},
              year = {2004},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-17}
      }
      

This paper discusses subtyping of tree-structured data encountered on the Web, e.g. XML and HTML data. Our long range objective is to de ne a type system for Web and/or Semantic Web query languages amenable to static type checking. We propose a type formalism motivated by XML Schema and accommodating two concepts of subtyping: inclusion subtyping (corresponding to XML Schema notion of type restriction) and extension subtyping (motivated by XML Schema's type extension). We present algorithms for checking both kinds of subtyping. The algorithms are polynomial if certain conditions are imposed on the type de nitions; the conditions seem natural and not too restrictive.

      @inproceedings{PMS-FB-2004-16,
              author = {Fran\c{c}ois Bry and W{\l}odzimierz Drabent and Jan Maluszynski},
              title = {On Subtyping of Tree-structured Data A Polynomial Approach},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, St. Malo, France (6th--10th September 2004)},
              year = {2004},
              organization = {REWERSE},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-16}
      }
      

This paper outlines aspects of querying and updating resources on the Web and on the Semantic Web, including the development of query and update languages in course of the Rewerse project. When considering updates and communication of updates between autonomous sources, reactive behavior plays an important role such that an event language is required. This article provides a systematic outline of the intended research steps towards handling reactivity and evolution on the Web.

      @inproceedings{PMS-FB-2004-15,
              author = {Wolfgang May and Jos\'{e} J\'{u}lio Alferes and Fran\c{c}ois Bry},
              title = {Towards generic query, update, and event languages for the Semantic Web},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, St. Malo, France (6th--10th September 2004)},
              year = {2004},
              organization = {REWERSE},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-15}
      }
      

Time is omnipresent on the (Semantic) Web. However, for- malism like XML, XML Schema, RDF, OWL and (Semantic) Web query languages have, if any, only very limited notions of temporal data types and temporal theories built-in. Recently, the development of Web Ser- vices for temporal operations has begun. In this article, we describe a connection, possibly the rst one, between such Web Services and Web formalisms: A proposal of a type system for temporal and calendric data, called multi-calendar temporal type system seamlessly integrated into a host (query) language. The type system's associated type checking meth- ods are beyond the scope of this article. For proof-of-concept purposes, the Web and Semantic Web query language Xcerpt has been chosen.

      @inproceedings{PMS-FB-2004-14,
              author = {Fran\c{c}ois Bry and Stephanie Spranger},
              title = {Towards a Multi-Calendar Temporal Type System for (Semantic) Web Query Languages},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, St. Malo, France (6th--10th September 2004)},
              year = {2004},
              organization = {REWERSE},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-14}
      }
      

To make use of data represented on the Semantic Web, it is necessary to provide languages for Web data retrieval and evolution. This article introduces into the (conventional and Semantic) Web query language Xcerpt and the event and update language XChange, and shows how their deductive capabilities make them well suited for querying, changing and reasoning with data on both the conventional and the Semantic Web. To this aim, small application scenarios are introduced.

      @inproceedings{PMS-FB-2004-13,
              author = {Fran\c{c}ois Bry and Tim Furche and Paula-Lavinia P\u{a}tr\^anjan and Sebastian Schaffert},
              title = {Data Retrieval and Evolution on the (Semantic) Web: A Deductive Approach},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, St. Malo, France (6th--10th September 2004)},
              year = {2004},
              organization = {REWERSE},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-13}
      }
      

This article reports on the XML retrieval system has been developed at the University of Munich last five years. In a typical session with X2, the user browses a structural summary of the XML database in select interesting elements and keywords occurring documents. Using this intermediate result, queries combining structure and textual references are composed semiautomatically. After query evaluation, the full set of answers presented in a visual and structured way. X2 largely exploits structure found in documents, queries and answers new interactive visualization and exploration techniques support mixed IR and database-oriented querying, bridging the gap between these three views on the data to retrieved. Another salient characteristic of X2 which distinguishes it from other visual query systems for XML is that various degrees of detailedness in the presentation answers, as well as techniques for dynamically reordering grouping retrieved elements once the complete answer been computed.

      @article{PMS-FB-2004-12,
              author = {Holger Meuss and Klaus U. Schulz and Felix Weigel and Simone Leonardi and Fran\c{c}ois Bry},
              title = {Visual Exploration and Retrieval of XML Document Collections with the Generic System X²},
              journal = {Journal on Digital Libraries, Special Issue on "Information Visualization Interfaces for Retrieval and Analysis"},
              year = {2004},
              volume = {4},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-12}
      }
      

The Semantic Web is an endeavor aiming at enriching the existing Web with meta-data and data processing so as to allow computer systems to actually reason with the data instead of merely rendering it. To this aim, it is necessary to be able to query and update data and meta-data. Existing Semantic Web query languages (like DQL2) are special purpose, i.e. they are designed for querying and reasoning with special representations like OWL or RDF, but are not capable of processing generic Web data. On the other hand, the language Xcerpt is a general purpose language that can query any kind of XML data and at the same time, being based on logic programming, provides advanced reasoning capabilities. It could thus serve to implement a wide range of different reasoning formalisms. Likewise, the maintenance and evolution of data on the (Semantic) Web is necessary: the Web is a living organism whose dynamic character requires languages for specifying its evolution. This requirement regards not only updating data from Web resources, but also the propagation of changes on the Web. These issues have not received much attention so far, existing update languages and reactive languages developed for XML data offer the possibility to execute just simple update operations and, moreover, important features needed for propagation of updates on the Web are still missing. The language XChange builds upon the query language Xcerpt and provides advanced, Web-specific capabilities, such as propagation of changes on the Web (change) and event-based communications between Web sites (exchange).

      @inproceedings{PMS-FB-2004-11,
              author = {Fran\c{c}ois Bry and Paula-Lavinia P\u{a}tr\^anjan and Sebastian Schaffert},
              title = {Xcerpt and XChange: Logic Programming Languages for Querying and Evolution on the Web},
              booktitle = {Proceedings of 19th International Conference on Logic Programming, St. Malo, France (6th--10th September 2004)},
              year = {2004},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-11}
      }
      

In this article, two deductive languages are introduced: the language Xcerpt, for querying data and reasoning with data on the (Semantic) Web, and the language XChange, for evolution and reactivity on the (Semantic) Web. A small application scenario is given as a motivation for these languages.

      @inproceedings{PMS-FB-2004-10,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert and Paula-Lavinia P\u{a}tr\^anjan},
              title = {Xcerpt and XChange: Deductive Languages for Data Retrieval and Evolution on the Web},
              booktitle = {Proceedings of Workshop on Semantic Web Services and Dynamic Networks, Ulm, Germany (22nd--24th September 2004)},
              year = {2004},
              organization = {GI},
              publisher = {Gesellschaft für Informatik (GI)},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-10}
      }
      

RÉSUMÉ: Les langages d'interrogation du Web comme XPath, XQuery et XSLT sont devenus des outils communs de réalisation d'applications Web. Cet article motive puis présente deux nouveaux langages d'interrogation expérimentaux pour le Web: Xcerpt et visXcerpt (cf. http://xcerpt.org). Ces deux langages reposent sur les mêmes principes. Un des aspects essentiel de ces langages est qu'ils sont déductifs: il s'appuient sur une notion d'unification semblable à, bien que différente de l'unification des systèmes de preuve automatique et de la programmation logique ainsi que sur une notion d'inférence semblable à celle de la programmation logique et aux vues du langage SQL d'interrogation de bases de données relationnelles. visXcerpt est un langage visuel qui réalise et présente d'une manière originale les constructions textuelles de Xcerpt. Xcerpt et visXcerpt visent à faciliter le développement d'applications du Web Sémantique. L'objectif de cet article est d'introduire aux aspects essentiels de Xcerpt et visXcerpt. ABSTRACT: Web Query languages like XPath, XQuery and XSLT are widely accepted tools for the development of Web applications today. This article presents and motivates two new and experimental query languages for the Web: Xcerpt and visXcerpt (see http://xcerpt.org). Both languages are based on the same principles. They are deductive languages, which is one of their central aspects: they use a sort of unification similar to the unification used in logic programming and deduction systems, as well as an inference mechanism similar to that of logic programming and to SQL views in databases. visXcerpt is a visual query language which provides a visual realization of Xcerpt's textual constructs. Xcerpt's and visXcerpt's main goal is to ease the development of applications for the Semantic Web applications. This article introduces the essential aspects of Xcerpt and visXcerpt.

      @inproceedings{PMS-FB-2004-9,
              author = {Sacha Berger and Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {Xcerpt et visXcerpt : Langages déductifs d'interrogation du Web},
              booktitle = {Proceedings of Treiziemes Journées Francophones de Programmation en Logique et Programmation par Contraintes, Angers, France (21st--23rd June 2004)},
              year = {2004},
              organization = {INRIA},
              pages = {183 ff},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-9}
      }
      

Anfragesprachen für XML-Daten sind heutzutage wesentliche Werkzeuge in der Entwicklung von Webanwendungen. Die am weitesten verbreiteten Sprachen sind XQuery und XSLT, die beide auf der pfadbasierten Selektionssprache XPath aufbauen. Dieser Vortrag gibt einen Einblick in eine neue Anfragesprache namens Xcerpt, die statt des pfadbasierten Ansatzes Anfragepattern verwendet, welche eine deklarativere Spezifikation von Anfragen erlauben. Xcerpt ist ausserdem eine deduktive, regelbasierte Sprache, die auch die Verknüpfung von mehreren Regeln (Chaining) und Rekursion ermöglicht. Eine Xcerpt-Regel kann damit auch als Abstraktion der Ausgangsdaten verstanden werden, ähnlich zu Views in relationalen Datenbanken. Auf Xcerpt aufbauend wird ausserdem die visuelle Anfragesprache visXcerpt vorgestellt. Aufgrund des patternbasierten Ansatzes von Xcerpt können in visXcerpt Anfragen auf einfache Weise visuell dargestellt und bearbeitet werden. Das Ziel beider Anfragesprachen ist es, die Entwicklung von Anwendungen insbesondere für das "Semantic Web" zu vereinfachen: Anfänger können mit Hilfe von visXcerpt Anfragen schnell und intuitiv formulieren und Fortgeschrittenen hilft die Deklarativität von Xcerpt bei der Gliederung komplexer Programme.

      @inproceedings{PMS-FB-2004-8,
              author = {Sacha Berger and Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {Xcerpt und visXcerpt: deduktive Anfragesprachen für das Web},
              booktitle = {Proceedings of 16. Workshop Grundlagen von Datenbanken, Monheim am Rhein, Germany (1st--4th June 2004)},
              year = {2004},
              organization = {GI},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-8}
      }
      

This article gives a practical introduction into the language Xcerpt, guided by many examples for illustrating language constructs and usage. Xcerpt is a rule-based, declarative query and transformation language for XML data. In Xcerpt, queries and the (re-)structuring of answer (also called "constructions") are expressed in terms of patterns instead of path navigations (like in XSLT and XQuery). Pattern queries are evaluated against XML documents using a non-standard form of unification (called "simulation unification" PMS-FB-2002-19). Furthermore, Xcerpt supports so-called rule chaining (with recursion), which makes it suitable even for complex query programs. Due to its foundations in logic programming, Xcerpt can also serve to implement reasoning algorithms for the Semantic Web.

      @inproceedings{PMS-FB-2004-7,
              author = {Sebastian Schaffert and Fran\c{c}ois Bry},
              title = {Querying the Web Reconsidered: A Practical Introduction to Xcerpt},
              booktitle = {Proceedings of Extreme Markup Languages 2004, Montreal, Quebec, Canada (2nd--6th August 2004)},
              year = {2004},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-7}
      }
      

Rooted in electronic publishing, XML is now widely used for modelling and storing structured text documents. Especially in the WWW, retrieval of XM L documents is most useful in combination with a relevance-based ranking of the query result. Index structures with ranking support are therefore needed for fast access to relevant parts of large document collections. This paper proposes a classification scheme for both XML ranking models and index structures, allowing to determine which index suits which ranking model. An analysis reveals that ranking parameters related to both the content and structure of the da ta are poorly supported by most known XML indices. The IR-CADG index, owing to its tight integration of content and structure, supports various XML ranking models in a very efficient retrieval process. Experiments show that it outperforms separate content/structure indexing by more than two orders of magnitude for large corpora of several hundred MB.

      @inproceedings{PMS-FB-2004-6,
              author = {Felix Weigel and Holger Meuss and Klaus U. Schulz and Fran\c{c}ois Bry},
              title = {Content and Structure in Indexing and Ranking XML},
              booktitle = {Proceedings of Seventh International Workshop on the Web and Databases, Paris, France (17th--18th June 2004)},
              year = {2004},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-6}
      }
      

Xcerpt is a declarative, pattern-based query and transformation language for the Web with deductive capabilities. In contrast to Web query languages like XQuery and XSLT, Xcerpt relies on concepts and techniques from logic programming and automated theorem proving such as declarative query patterns and rule chaining. Xcerpt can also be used for querying Web metadata, like OWL or RDF data, and reasoning on such metadata. In contrast to specific languages for OWL and RDF, however, Xcerpt is a general purpose query, transformation, and reasoning language, i.e. it can be used for reasoning not only with Web metadata but also with plain Web data. Salient aspects of Xcerpt are its nonstandard query patterns for retrieving incompletely specified data and its unusual grouping constructs some and all that significantly depart from the standard approaches in logic programming or automated theorem proving. Xcerpt relies on a new, assymmetric unification, called simulation unification for evaluating query patterns that incompletely specify data. Furthermore, Xcerpt does not rely on meta reasoning for expressing and processing grouping constructs corresponding to Prolog`s metalevel predicates setof and bagof. This article gives a brief overview over challenges of applying logic programming techniques to Web querying. In particular it suggests two different approaches for treating the meta-level grouping constructs all and some in a proof calculus formalising the operational semantics of Xcerpt.

      @inproceedings{PMS-FB-2004-5,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert and Andreas Schr\"oder},
              title = {A contribution to the Semantics of Xcerpt, a Web Query and Transformation Language},
              booktitle = {Applications of Declarative Programming and Knowledge Management, Proceedings of 15th International Conference on Applications of Declarative Programming and Knowledge Management, INAP 2004, and 18th Workshop on Logic Programming, Potsdam, Germany (14th--16th March 2004)},
              year = {2004},
              volume = {3392},
              organization = {GLP, GI},
              pages = {258--268},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-5}
      }
      

The FuTIRe library is a collection of classes and methods for representing and manipulating fuzzy time intervals and relations between them. Time intervals like `tonight', which are usually not very precise, can be modeled as fuzzy sets. But this causes the problem that the relations between points and intervals and between two intervals, which are usually very trivial, become very complex when the intervals are fuzzy sets. Moreover, there are many di erent possibilities to de ne such relations. In FuTIRe it is not only possible to represent fuzzy time intervals, but one can de ne customized fuzzy point-interval and interval-interval relations. These relations can even yield fuzzy values when the intervals are in fact crisp. As an example for an application, consider a database with, say, a cinema timetable, and you query the timetable `give me all performances ending before midnight'. The usual `before' relation will exclude the performances ending a second after midnight. With the fuzzy before relation in FuTIRe you can get instead of a sharp drop to 0 at midnight decreasing fuzzy values after midnight, and these can be used to order the results of the query. FuTIRe is an open source C++ library.

      @techreport{PMS-FB-2004-4,
              author = {Hans J\"urgen Ohlbach},
              title = {Fuzzy Time Intervals and Relations - The FuTIRe Library},
              institution = {Institute for Informatics, University of Munich},
              year = {2004},
              type = {Research Report},
              number = {PMS-FB-2004-4},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-4}
      }
      

Xcerpt is a declarative, pattern-based query and transformation language for the Web with deductive capabilities. In contrast to Web query languages like XQuery and XSLT, Xcerpt relies on concepts and techniques from logic programming and automated theorem proving such as declarative query patterns and rule chaining. Xcerpt can also be used for querying Web metadata, like OWL or RDF data, and reasoning on such metadata. In contrast to specific languages for OWL and RDF, however, Xcerpt is a general purpose query, transformation, and reasoning language, i.e. it can be used for reasoning not only with Web metadata but also with plain Web data. Salient aspects of Xcerpt are its nonstandard query patterns for retrieving incompletely specified data and its unusual grouping constructs some and all that significantly depart from the standard approaches in logic programming or automated theorem proving. Xcerpt relies on a new, assymmetric unification, called simulation unification for evaluating query patterns that incompletely specify data. Furthermore, Xcerpt does not rely on meta reasoning for expressing and processing grouping constructs corresponding to Prolog`s metalevel predicates setof and bagof. This article gives a brief overview over challenges of applying logic programming techniques to Web querying. In particular it suggests two different approaches for treating the meta-level grouping constructs all and some in a proof calculus formalising the operational semantics of Xcerpt.

      @article{PMS-FB-2004-3,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert and Andreas Schr\"oder},
              title = {A contribution to the Semantics of Xcerpt, a Web Query and Transformation Language},
              journal = {},
              year = {2004},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-3}
      }
      

Unter einem "Datenstrom" versteht man kontinuierlich übersandte Datensätze, deren Größe, Menge sowie schnelles Aufkommen verbieten, sie vor der Verarbeitung zu speichern. Die bisherige Forschung hat in erster Linie zum Ziel, Verfahren zu entwickeln, die es erlauben, ohne Verzögerung des Datenflusses (1) einen Strom auf das Vorkommen von bestimmten Daten zu uberwachen und (2) die Daten aus einem Strom zu analysieren. Dieser Artikel dient als kurze Einführung über Merkmale und aktuelle Forschungsergebnisse der Datenströmenanfrage und -analyse.

      @article{PMS-FB-2004-2,
              author = {Fran\c{c}ois Bry and Tim Furche and Dan Olteanu},
              title = {Datenströme},
              journal = {Informatik Spektrum},
              year = {2004},
              volume = {27},
              number = {2},
              pages = {168--171},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-2}
      }
      

Data streams might be preferable to data stored in memory in contexts where the data is too large or volatile, or a standard approach to data processing based on data parsing and/or storing is too time or space consuming. Emerging applications such as publish-subscribe systems, data monitoring in sensor networks, financial and traffic monitoring, and routing of MPEG-7 call for querying data streams. In many such applications, XML streams are arguably more appropriate than flat data streams, for XML data is record-like, though not precluding multiple occurrences of fields with the same name. Evaluating selection queries against XML streams is especially challenging because XML data is structured (like records) and might have unbounded size. This paper proposes an efficient single-pass evaluator of XPath queries against XML data streams unbounded (possibly infinite) in size. The evaluator is based on networks of independent deterministic pushdown transducers and it is especially suitable for implementation on devices with low-memory and simple logic as used, e.g., in mobile computing.

      @inproceedings{PMS-FB-2004-1,
              author = {Dan Olteanu and Tim Furche and Fran\c{c}ois Bry},
              title = {An Efficient Single-Pass Query Evaluator for XML Data Streams},
              booktitle = {Data Streams Track, Proceedings of 19th Annual ACM Symposium on Applied Computing, Nicosia, Cyprus (14th--17th March 2004)},
              year = {2004},
              organization = {ACM},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2004-1}
      }
      

Bioinformatics or computational biology, i.e. the application of mathematical and computer science methods to solving problems in molecular biology that require large scale data, computation, and analysis, is a research area currently receiving a considerable attention. Databases play an essential role in molecular biology and consequently in bioinformatics. molecular biology data are often relatively cheap to produce, leading to a proliferation of databases: the number of bioinformatics databases accessible worldwide probably lies between 500 and 1.000. Not only molecular biology data, but also molecular biology literature and literature references are stored in databases. Bioinformatics databases are often very large (e.g. the sequence database GenBank contains more than 4 106 nucleotide sequences) and in general grows rapidly (e.g. about 8000 abstracts are added every month to the literature database PubMed). Bioinformatics databases are heterogeneous in their data, in their data modeling paradigms, in their management systems, and in the data analysis tools they supports. Furthermore, bioinformatics databases are often implemented, queried, updated, and managed using methods rarely applied for other databases. This presentation aims at introducing in current bioinformatics databases, stressing their aspects departing from conventional databases.

      @inproceedings{PMS-FB-2003-17,
              author = {Fran\c{c}ois Bry and Peer Kr\"oger},
              title = {Bioinformatics Databases: State of the Art and Research Perspectives},
              booktitle = {Proceedings of 7th East European Conference on Advances in Databases and Information Systems, Dresden, Germany (3rd--6th September 2003)},
              year = {2003},
              volume = {2798},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-17}
      }
      

      @proceedings{PMS-FB-2003-16,
              title = {Principles and Practice of Semantic Web Reasoning},
              year = {2003},
              editor = {Fran\c{c}ois Bry and Nicola Henze and Jan Maluszynski},
              publisher = {Springer-Verlag},
              volume = {2901},
              series = {LNCS},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-16}
      }
      

Querying of XML streams is receiving much attention due to its growing range of applications from traffic monitoring to routing of media streams. Existing approaches to querying XML streams consider restricted query language fragments, in most cases with exponential worst-case complexity in the size of the query. This paper investigates the complexity of the SPEX evaluation method. The combined complexity of this method is shown to be polynomial in the size of the data and the query. Extensive experimental evaluation with a prototype confirm the theoretical complexity results.

      @inproceedings{PMS-FB-2003-15,
              author = {Dan Olteanu and Tim Furche and Fran\c{c}ois Bry},
              title = {Evaluating Complex Queries against XML streams with Polynomial Combined Complexity},
              booktitle = {Proceedings of 21st Annual British National Conference on Databases, Edinburgh, United Kingdom (7th--9th July 2004)},
              year = {2003},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-15}
      }
      

XML is well-suited for modelling structured data with textual content. However, most indexing approaches perform structure and content matching independently, combining the retrieved path and keyword occurrences in a third step. This paper shows that retrieval in XML documents can be accelerated significantly by processing text and structure simultaneously during all retrieval phases. To this end, the Content-Aware DataGuide (CADG) enhances the wellknown DataGuide with (1) simultaneous keyword and path matching and (2) a precomputed content/structure join. Extensive experiments prove the CADG to be 50-90% faster than the DataGuide for various sorts of query and document, including difficult cases such as poorly structured queries and recursive document paths. A new query classification scheme identifies precise query characteristics with a predominant influence on the performance of the individual indices. The experiments show that the CADG is applicable to many real-world applications, in particular large collections of heterogeneously structured XML documents.

      @techreport{PMS-FB-2003-14,
              author = {Felix Weigel and Holger Meuss and Fran\c{c}ois Bry and Klaus U. Schulz},
              title = {Content-Aware DataGuides for Indexing Large Collections of XML Documents},
              institution = {Institute for Informatics, University of Munich},
              year = {2003},
              type = {Research Report},
              number = {PMS-FB-2003-14},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-14}
      }
      

Not only since the advent of XML, many applications call for e client structured document retrieval, challenging both Information Retrieval (IR) and database (DB) research. Most approaches combining indexing techniques from either field still separate path and content matching, merging the hits in an expensive join. This paper shows that retrieval is significantly accelerated by processing text and structure simultaneously. The Content-Aware DataGuide (CADG) interleaves IR and DB indexing techniques to minimize path matching and suppress joins at query time, also saving needless I/O operations during retrieval. Extensive experiments prove the CADG to outperform the DataGuide [9,12] by a factor 3 to 150 on average. For structurally unselective queries, it is 400 times faster than the DataGuide. The best results were achieved on large collections of heterogeneously structured textual documents.

      @inproceedings{PMS-FB-2003-13,
              author = {Felix Weigel and Holger Meuss and Fran\c{c}ois Bry and Klaus U. Schulz},
              title = {Content-Aware DataGuides: Interleaving IR and DB Indexing Techniques for Efficient Retrieval of Textual XML Data},
              booktitle = {Proceedings of European Conference on Information Retrieval Research, Sunderland, U.K. (5th--7th April 2004)},
              year = {2003},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-13}
      }
      

Collaborative categorization is an emerging direction for research and innovative applications. Arguably, collaborative categorization on the Web is an especially promising emerging form of collaborative Web systems because of both, the widespread use of the conventional Web and the emergence of the Semantic Web providing with more semantic information on Web data. This paper discusses this issue and proposes two approaches: collaborative categorization via category merging and collaborative categorization proper. The main advantage of the first approach is that it can be rather easily realized and implemented using existing systems such as Web browsers and mail clients. A prototype system for collaborative Web usage that uses category merging for collaborative categorization is described and the results of field experiments using it are reported. The second approach, called collaborative categorization proper, however, is more general and scales better. The data structure and user interface aspects of an approach to collaborative categorization proper are discussed.

      @techreport{PMS-FB-2003-12,
              author = {Fran\c{c}ois Bry and Holger Wagner},
              title = {Collaborative Categorization on the Web: Approach, Prototype, and Experience Report},
              institution = {Institute for Informatics, University of Munich},
              year = {2003},
              type = {Research Report},
              number = {PMS-FB-2003-12},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-12}
      }
      

Adaptive web applications combine data retrieval on the web with reasoning so as to generate context dependent contents. The data is retrieved either as content or as context specifications. Content data is, for example, fragments of a textbook or e-commerce catalogue, whereas context data is, for example, a user model or a device profile. Current adaptive web applications are often implemented using ad hoc and heterogeneous techniques. This paper describes a novel approach called XML Document Adaptation Queries (XDAQ) requiring less heterogeneous software components. The approach is based on using a web query language for data retrieval (content as well as context) and on a novel generic formalism to express adaptation. The approach is generic in the sense that it is applicable with all web query and transformation languages, for example with XQuery and XSLT.

      @inproceedings{PMS-FB-2003-11,
              author = {Michael Kraus and Fran\c{c}ois Bry and Kazuhiro Kitagawa},
              title = {XML Document Adaptation Queries (XDAQ): An Approach to Adaptation Reasoning Using Web Query Languages},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, Mumbai, India (9th--13th December 2003)},
              year = {2003},
              volume = {2901},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-11}
      }
      

Reasoning on time and location is receiving increasing attention on the Web due to emerging fields like Web adaptation, mobile computing, and the Semantic Web. Web applications in these elds often refer to rather complex temporal, calendric, and location information. Unfortunately, today's Web languages and formalisms have merely primitive temporal and location data types and temporal and location reasoning capabilities { if any. This article reports on work in progress aiming at integrating temporal and locational reasoning into XML query and transformation operations. We analyze the problem and propose a concrete architecture. A prototype of the temporal reasoner, the Web- Cal system has already been realized.

      @inproceedings{PMS-FB-2003-10,
              author = {Fran\c{c}ois Bry and Bernhard Lorenz and Hans J\"urgen Ohlbach and Stephanie Spranger},
              title = {On Reasoning on Time and Location on the Web},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, Mumbai, India (9th--13th December 2003)},
              year = {2003},
              volume = {2901},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-10}
      }
      

      @proceedings{PMS-FB-2003-9,
              title = {Proceedings of 10th International Workshop on `Knowledge Representation meets Databases' (KRDB2003)},
              year = {2003},
              editor = {Fran\c{c}ois Bry and Carsten Lutz and Ulrike Sattler and Mareike Schoop},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-9}
      }
      

In this paper, we present a framework for automatic generation of CHR solvers given the logical specification of the constraints. This approach takes advantage of the power of tabled resolution for constraint logic programming, in order to check the validity of the rules. Compared to previous work, where different methods for automatic generation of constraint solvers have been proposed, our approach enables the generation of more expressive rules (even recursive and splitting rules) that can be used directly as CHR solvers.

      @article{PMS-FB-2003-8,
              author = {Slim Abdennadher and Thom Fr\"uhwirth},
              title = {Automatic Generation of CHR Constraint Solvers},
              journal = {Special Issue of Theory and Practice of Logic Programming on Constraint Handling Rules},
              year = {2003},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-8}
      }
      

One lesson learned from practical constraint solving applications is that constraints are often heterogeneous. Solving such constraints requires a collaboration of constraint solvers. In this paper, we introduce a methodology for the tight integration of CHR constraint programs into one such program. CHR is a high-level rule-based language for writing constraint solvers and reasoning systems. A constraint solver is well-behaved if it is terminating and confluent. When merging constraint solvers, this property may be lost. Based on previous results on CHR program analysis and transformation we show how to utilize completion to regain well-behavedness. We identify a class of solvers whose union is always confluent and we show that for preserving termination such a class is hard to find. The merged and completed constraint solvers may contain redundant rules. Utilizing the notion of operational equivalence, which is decidable for well-behaved CHR programs, we present a method to detect redundant rules in a CHR program.

      @inproceedings{PMS-FB-2003-7,
              author = {Slim Abdennadher and Thom Fr\"uhwirth},
              title = {Integration and Optimization of Rule-based Constraint Solvers},
              booktitle = {Proceedings of International Symposium on Logic-based Program Synthesis and Transformation, Uppsala, Sweden (25th August 2003--27th August 2002)},
              year = {2003},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-7}
      }
      

As XML is increasingly being used to represent information on the Web, query and reasoning languages for such data are needed. This article argues that in contrast to the navigational approach taken in particular by XPath and XQuery, a positional approach as used in the language Xcerpt is better suited for a straightforward visual representation. The constructs of the pattern- and rule-based query language Xcerpt are introduced and it is shown how the visual representation visXcerpt renders these constructs to form a visual query language for XML.

      @inproceedings{PMS-FB-2003-6,
              author = {Sacha Berger and Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {A Visual Language for Web Querying and Reasoning},
              booktitle = {Proceedings of Workshop on Principles and Practice of Semantic Web Reasoning, Mumbai, India (9th--13th December 2003)},
              year = {2003},
              volume = {2901},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-6}
      }
      

Reasoning on the Web is receiving an increasing attention because of emerging fields such as Web adaption and Semantic Web. Indeed, the advanced functionalities striven for in these fields call for reasoning capabilities. Reasoning on the Web, however, is usually done using existing techniques rarely fitting the Web. As a consequence, additional data processing like data conversion from Web formats (e.g. XML or HTML) into some other formats (e.g. classical logic terms and formulas) is often needed and aspects of the Web (e.g. its inherent inconsistency) are neglected. This article first gives requirements for an entailment tuned to reasoning on the Web. Then, it describes how classical logic's entailment can be modified so as to enforce these requirements. Finally, it discusses how the proposed entailment can be used in applying logic programming to reasoning on the Web.

      @inproceedings{PMS-FB-2003-5,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {An Entailment Relation for Reasoning on the Web},
              booktitle = {Proceedings of Rules and Rule Markup Languages for the Semantic Web, Sanibel Island (Florida), USA (20th October 2003)},
              year = {2003},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-5}
      }
      

The area of software applications for teaching (teaching applications for short), whether for distance teaching or for traditional presence teaching, is characterized by a multitude of different requirements and expectations. A corresponding multitude of different teaching applications have been and continue to be implemented, most of them sharing parts of their functionalities that tend to be re-implemented over and over again. The paper argues that a compositional approach based on web services would overcome this deficiency quite naturally. The paper classifies the services that need to be implemented by teaching applications and proposes an open architecture based on web services for information interchange, integration, and interoperability among existing teaching applications.

      @inproceedings{PMS-FB-2003-4,
              author = {Fran\c{c}ois Bry and Norbert Eisinger and Georg Schneemayer},
              title = {Web Services for Teaching: A Case Study},
              booktitle = {Proceedings of First International Conference on Web Services, Las Vegas, USA (23rd--26th June 2003)},
              year = {2003},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-4}
      }
      

This paper reports on enriching a (logic-based) query and transformation language for the Web, called Xcerpt, with temporal constructs and temporal reasoning capabilities. Advanced Web applications often refer to temporal data, especially to time points, complex time intervals, and durations. Salient to many advanced Web applications is that they often refer to various calendars. However, current Web languages and formalisms have rather primitive temporal constructs and temporal data processing capabilities - if any. The focus of the project this paper reports on is not to specify yet another temporal logic and/or calculus. Instead, it is to select from existing temporal logics and calculi a coherent set of concepts and processing primitives to be added to a Web query and transformation language.

      @inproceedings{PMS-FB-2003-3,
              author = {Fran\c{c}ois Bry and Stephanie Spranger},
              title = {Temporal Constructs for a Web Language},
              booktitle = {Proceedings of 4th Workshop on Interval Temporal Logics and Duration Calculi, Vienna, Austria (25th--29th August 2003)},
              year = {2003},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-3}
      }
      

Xcerpt is an experimental pattern-based query and transformation language for XML and semistructured data. Xcerpt uses patterns both for binding variables in query expressions and for reassembling the variables (bound to data items in query expressions) in so-called construct terms. Based on Xcerpt, a visual query language called visXcerpt has been conceived and prototypically implemented. Most interestingly, the pattern-based approach to query and transformation languages for XML and semistructured data appears to be especially well suited for a visual (or graphical) language.

      @inproceedings{PMS-FB-2003-2,
              author = {Sacha Berger and Fran\c{c}ois Bry and Sebastian Schaffert and Christoph Wieser},
              title = {Xcerpt and visXcerpt: From Pattern-Based to Visual Querying of XML and Semistructured Data},
              booktitle = {Proceedings of 29th International Conference on Very Large Data Bases, Berlin, Germany (9th--12th September 2003)},
              year = {2003},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-2}
      }
      

Query and transformation languages developed since the mid 90es for XML and semistructured data -- e.g. XQuery, the precursors of XQuery, and XSLT -- built upon a path-oriented node selection: A node in a data item is specified in terms of a root-to-node path in the manner of the file selection languages of operating systems. Constructs from regular expressions such as *, +, ?, and "wildcards" give rise to a flexible node retrieval from incompletely specified data items. This paper investigates an alternative approach to querying XML and semistructured data. A metaphor for this approach views queries as patterns, answers as data items matching the queries. Formally, an answer to a query is defined as a simulation of an instance of the query in a database item. A basic query language is introduced and it is given a compositional semantics. Recent results on an operational semantics are outlined.

      @inproceedings{PMS-FB-2003-1,
              author = {Sacha Berger and Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {Pattern Queries for XML and Semistructured Data},
              booktitle = {Proceedings of 17. Workshop Logische Programmierung, Dresden, Germany (11th--13th December 2002)},
              year = {2003},
              organization = {GLP, GI},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2003-1}
      }
      

The growing importance of XML as a data interchange standard demands languages for data querying and transformation. Since the mid 90es, several such languages have been proposed that are inspired from functional languages (such as XSLT) and/or database query languages (such as XQuery). This paper addresses applying logic programming concepts and techniques to designing a declarative, rule-based query and transformation language for XML and semistructured data. The paper first introduces issues specific to XML and semistructured data such as the necessity of flexible "query terms" and of "construct terms". Then, it is argued that logic programming concepts are particularly appropriate for a declarative query and transformation language for XML and semistructured data. Finally, a new form of unification, called "simulation unification", is proposed for answering "query terms", and it is illustrated on examples.

      @inproceedings{PMS-FB-2002-19,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {Towards a Declarative Query and Transformation Language for XML and Semistructured Data: Simulation Unification},
              booktitle = {Proceedings of International Conference on Logic Programming, Copenhagen, Denmark (29th July--1st August 2002)},
              year = {2002},
              volume = {2401},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-19}
      }
      

A simple extension is proposed for enhancing HTML and XML with adaptation. It consists in using the path selectors of style sheet languages such as CSS and XSLT for expressing content and navigation adaptation. The needed extensions to a path selector language are minimal, a few additional constructs suffice. The processor of the language can be kept almost unchanged, no new algorithms are needed. Furthermore, it is proposed to use XML for expressing user model data like browsing history, browsing environment (such as device, time, etc.), and application data (such as user performances on exercises).

      @inproceedings{PMS-FB-2002-18,
              author = {Fran\c{c}ois Bry and Michael Kraus},
              title = {Adaptive Hypermedia made simple using HTML/XML Style Sheet Selectors},
              booktitle = {Proceedings of 2nd Int. Conf. on Adaptive Hypermedia and Adaptive Web Based Systems, Malaga, Spain (29th--31st May 2002)},
              year = {2002},
              pages = {427--475},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-18}
      }
      

In he past decade, there has been a lot of in interest in phase transitions within artificial intelligence, and more recently, in machine learning and inductive logic programming. We investigate phase transitions in learning k-term DNF boolean formulae, a practically relevant class of concepts. We do no only show that here exist phase transitions, but also characterize and locate these phase transitions using the parameters k, the number of positive and negative examples, and the number of boolean variables. Subsequently, we investigate stochastic local search (SLS) for k-term DNF learning. We compare several variants that first reduce k-term DNF to SAT and then apply well-known SLS algorithms, such as GSAT and WalkSAT. Our experiments indicate that WalkSAT is able o solve the largest fraction of hard problem instances.

      @inproceedings{PMS-FB-2002-17,
              author = {Ulrich R\"uckert and Stefan Kramer and Luc De Raedt},
              title = {Phase Transitions and Stochastic Local Search in k-Term DNF Learning},
              booktitle = {Proceedings of 13th European Conference on Machine Learning, Helsinki, Finland (19th--23rd August 2002)},
              year = {2002},
              volume = {2430},
              series = {LNCS},
              pages = {43--63},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-17}
      }
      

This paper describes X² (eXploring XML data), a system for efficiently querying XML data and visually exploring answer sets, with a special focus on the novel user interface for interaction with the query result. The process of querying XML documents is performed interactively and in a completely graphical manner. Special attention was paid to simplicity of the user interface: In a first step the user submits a query to the system and gets the result presented in the form of a Complete Answer Aggregate (CAA). CAAs visually (re)present the answer space in a compact form and thus provide a good overview over the set of all answers. They offer a rich variety of presentation modes and exploration techniques which are used in the second step to interactively explore the answer space.

      @inproceedings{PMS-FB-2002-16,
              author = {Holger Meuss and Klaus U. Schulz and Fran\c{c}ois Bry},
              title = {Visual Querying and Exploration of Large Answers in XML Databases with X²: A Demonstration},
              booktitle = {Proceedings of 19th International Conference on Data Engineering, Bangalore, India (5th--8th March 2003)},
              year = {2002},
              organization = {IEEE},
              pages = {777--779},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-16}
      }
      

A general approach to implement propagation and simplification of constraints consists of applying rules over these constraints. However, a difficulty that arises frequently when writing a constraint solver is to determine the constraint propagation algorithm. In this paper, we propose a method for generating propagation and simplification rules for constraints over finite domains defined extensionally by e.g. a truth table or their tuples. The generation of rules is performed in two steps. First, propagation rules are generated. Propagation rules do not rewrite constraints but add new ones. Thus, the constraint store may contain superfluous constraints. Removing these constraints not only allows saving of space but also decreases the cost of constraint solving. Constraints can be removed using simplification rules. Thus, in a second step some propagation rules are transformed into simplification rules. Furthermore, we show that our approach performs well on various examples, including Boolean constraints, multi-valued logic, and Allen's qualitative approach to temporal logic. Moreover, an application taken from the field of digital circuit design shows that our approach is of practical use.

      @article{PMS-FB-2002-15,
              author = {Slim Abdennadher and Christophe Rigotti},
              title = {Automatic Generation of Rule-Based Constraint Solvers over Finite Domains},
              journal = {ACM Transactions on Computational Logic (TOCL)},
              year = {2002},
              note = {to appear},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-15}
      }
      

Die Bioinformatik kann als Anwendung von Informatikmethoden zur Untersuchung von Problemen der Molekularbiologie definiert werden, die auf sehr große Datenmengen beruhen und einer umfangreichen Datenanalyse bedürfen. Folglich spielen Datenbanken in der Bioinformatik eine zentrale Rolle. Die Bioinformatik-Datenbanken haben interessante Merkmale, die in herkömmlichen Datenbanken selten vorkommen. Insbesondere zeigen Datenbanken mit unterschiedlichen Molekularbiologie-Daten einheitliche Merkmale.

      @article{PMS-FB-2002-14,
              author = {Fran\c{c}ois Bry and Peer Kr\"oger},
              title = {Aktuelles Schlagwort: Datenbanken in der Bioinformatik},
              journal = {Informatik Spektrum},
              year = {2002},
              volume = {25},
              number = {5},
              pages = {359--362},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-14}
      }
      

A general approach to implement propagation and simplification of constraints consists of applying rules over these constraints. However, a difficulty that arises frequently when writing a constraint solver is to determine the constraint propagation algorithm. In previous work, different methods for automatic generation of rule-based solvers for constraints defined over finite domains have been proposed. In this paper, we present a method for generating rule-based solvers for constraint predicates defined by means of a constraint logic program, even when the constraint domain is infinite.

      @article{PMS-FB-2002-13,
              author = {Slim Abdennadher and Christophe Rigotti},
              title = {Automatic Generation of Rule-Based Solvers for Intentionally Defined Constraints},
              journal = {International Journal on Artificial Intelligence Tools},
              year = {2002},
              volume = {11},
              number = {2},
              pages = {283--302},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-13}
      }
      

This paper is devoted to a streamed and progressive evaluation of regular path expressions for XML based on pushdown transducer networks. An evaluation model called SPEX is described which focuses on regular path expressions with qualifiers, as XPath proposes. The SPEX approach enjoys the following attractive features. The translation of a regular path expression with qualifiers into a transducer network takes a time linear in the size of the input expression. The evaluation can be performed in one pass over the data stream. The memory space needed for an evaluation is at most quadratic in the document depth. The computational power needed by each transducer of a SPEX network is within the 1-DPDT class. Experiments with a prototype implementation points to a very good efficiency of the approach.

      @inproceedings{PMS-FB-2002-12,
              author = {Dan Olteanu and Tobias Kiesling and Fran\c{c}ois Bry},
              title = {An Evaluation of Regular Path Expressions with Qualifiers against XML Streams},
              booktitle = {Proceedings of 19th International Conference on Data Engineering, Bangalore, India (5th--8th March 2003)},
              year = {2002},
              organization = {IEEE},
              pages = {702--704},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-12}
      }
      

This articles introduces into Xcerpt, a rule-based query and transformation language for XML. First, the design principles of Xcerpt are given. Then, the essential construct of Xcerpt are explained and illustrated on examples: "query terms", i.e. patterns using which Xcerpt queries are posed, "construct terms", i.e. pattern re-assembling the data selected in a query term into a new data item, and "construct-query rule" linking queries with construct terms. Then, Xcerpt and XQuery are compared on examples and the advantages of Xcerpt are discussed. Finally, an outlook into Xcerpt's declarative and procedural semantics as well as into Xcerpt's features currently developed are given.

      @inproceedings{PMS-FB-2002-11,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {A Gentle Introduction into Xcerpt, a Rule-based Query and Transformation Language for XML},
              booktitle = {Proceedings of International Workshop on Rule Markup Languages for Business Rules on the Semantic Web, Sardinia, Italy (14th June 2002)},
              year = {2002},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-11}
      }
      

One lesson learned from practical applications is that constraints are often heterogeneous. Solving such constraints requires a collaboration of constraint solvers. In this paper, we introduce a methodology for the tight integration of CHR constraint solver programs into one such program. CHR is a high-level rule-based language for writing constraint solvers and reasoning systems. A constraint solver is well-behaved if it is terminating and confluent. When merging constraint solvers, this property may be lost. Based on previous results on CHR program analysis and transformation we show how to utilize completion to regain well-behavedness. We identify a class of solvers whose union is always confluent and we show that for preserving termination such a class is hard to find. The merged and completed constraint solvers may contain redundant rules. Utilizing the notion of operational equivalence, which is decidable for well-behaved CHR programs, we present a method to detect redundant rules in a CHR program.

      @inproceedings{PMS-FB-2002-10,
              author = {Slim Abdennadher and Thom Fr\"uhwirth},
              title = {Using Program Analysis for Integration and Optimization of Rule-based Constraint Solvers},
              booktitle = {Proceedings of Onzièmes Journées Francophones de Programmation Logique et Programmation par Contraintes, Nice, France (27th--29th May 2002)},
              year = {2002},
              organization = {INRIA},
              pages = {257--271},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-10}
      }
      

Most existing libraries providing constraint facilities are embedded in the logic programming language, Prolog, or in the object-oriented language, C++. Recently, some proposals have been made to integrate constraint handling in Java. The goal of this work is to provide a new constraint library for Java, called JACK. It consists of a high-level language for writing constraint solvers, a generic search engine and a tool to visualize the simplification and propagation of constraints.

      @article{PMS-FB-2002-9,
              author = {Slim Abdennadher and Ekkerhard Kr\"amer and Matthias Saft and Matthias Schmauss},
              title = {JACK: A Java Constraint Kit},
              journal = {Electronic Notes in Theoretical Computer Science},
              year = {2002},
              volume = {64},
              pages = {1--17},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-9}
      }
      

Computational Biology or Bioinformatics has been defined as the application of mathematical and Computer Science methods to solving problems in Molecular Biology that require large scale data, computation, and analysis \cite{clu96}. As expected, Molecular Biology databases play an essential role in Computational Biology research and development. This paper introduces into current Molecular Biology databases, stressing data modeling, data acquisition, data retrieval, and the integration of Molecular Biology data from different sources. This paper is primarily intended for an audience of computer scientists with a limited background in Biology.

      @article{PMS-FB-2002-8,
              author = {Fran\c{c}ois Bry and Peer Kr\"oger},
              title = {A Computational Biology Database Digest: Data, Data Analysis, and Data Management},
              journal = {Distributed and Parallel Databases},
              year = {2002},
              volume = {13},
              number = {1},
              pages = {7--42},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-8}
      }
      

Most query and transformation languages developed since the mid 90es for XML and semistructured data -- e.g. XQuery, the precursors of XQuery, and XSLT -- build upon a path-oriented node selection: A node in a data item is specified in terms of a root-to-node path in the manner of the file selection languages of operating systems. Constructs inspired from the regular expression constructs *, +, ?, and "wildcards" give rise to a flexible node retrieval from incompletely specified data items. This paper further introduces into Xcerpt, a query and transformation language further developing an alternative approach to querying XML and semistructured data first introduced with the language UnQL. A metaphor for this approach views queries as patterns, answers as data items matching the queries. Formally, an answer to a query is defined as a simulation of an instance of the query in a data item.

      @inproceedings{PMS-FB-2002-7,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {The XML Query Language Xcerpt: Design Principles, Examples, and Semantics},
              booktitle = {Web, Web-Services, and Database Systems, Proceedings of 2nd Annual International Workshop "Web and Databases", Erfurt, Germany (9th--10th October 2002)},
              year = {2002},
              volume = {2593},
              organization = {German Informatics Society (GI)},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-7}
      }
      

While the World Wide Web (WWW or Web) is steadily expanding, electronic books (eBooks) remain a niche market. In this article, it is first postulated that (1) specialized contents and device independence can make Web based eBooks compete with paper prints, and that (2) adaptive features that can be implemented by client-side computing are relevant for eBooks, while more complex forms of adaptation requiring server-side computations are not. Then, enhancements of the WWW standards (specifically of XML, XHTML, of the style-sheet languages CSS and XSL, and of the linking language XLink) are proposed for a better support of client-side adaptation and device independent content modeling are proposed. Finally, advanced browsing functionalities desirable for eBooks as well as their implementation in the WWW context are described.

      @article{PMS-FB-2002-6,
              author = {Fran\c{c}ois Bry and Michael Kraus},
              title = {Perspectives for Electronic Books in the World Wide Web Age},
              journal = {The Electronic Library},
              year = {2002},
              volume = {20},
              number = {4},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-6}
      }
      

Query and transformation languages developed since the mid 90es for XML and semistructured data -- e.g. XQuery, the precursors of XQuery, and XSLT -- built upon a path-oriented node selection: A node in a data item is specified in terms of a root-to-node path in the manner of the file selection languages of operating systems. Constructs from regular expressions such as *, +, ?, and "wildcards" give rise to a flexible node retrieval from incompletely specified data items. This paper investigates an alternative approach to querying XML and semistructured data. A metaphor for this approach views queries as patterns, answers as data items matching the queries. Formally, an answer to a query is defined as a simulation of an instance of the query in a database item. A basic query language is introduced and it is given a compositional semantics. Recent results on an operational semantics are outlined.

      @techreport{PMS-FB-2002-5,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {Pattern Queries for XML and Semistructured Data},
              institution = {Institute for Informatics, University of Munich},
              year = {2002},
              type = {Research Report},
              number = {PMS-FB-2002-5},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-5}
      }
      

The location path language XPath is of particular importance for XML applications since it is a core component of many XML processing standards such as XSLT or XQuery. In this paper, based on axis symmetry of XPath, equivalences of XPath 1.0 location paths involving ``reverse axes'', such as ancestor and preceding, are established. These equivalences are used as rewriting rules in an algorithm for transforming location paths with reverse axes into equivalent reverse-axis-free ones. Location paths without reverse axes as generated by the presented rewriting algorithm enable efficient SAX-like streamed data processing of XPath.

      @inproceedings{PMS-FB-2002-4,
              author = {Dan Olteanu and Holger Meuss and Tim Furche and Fran\c{c}ois Bry},
              title = {XPath: Looking Forward},
              booktitle = {Proceedings of Workshop on XML-Based Data Management at EDBT 2002, Prague, Czech Republic (24th--28th March 2002)},
              year = {2002},
              volume = {2490},
              series = {LNCS},
              publisher = {Springer-Verlag},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-4}
      }
      

Context adaptation of web contents is nowadays necessary because of the various devices used (especially mobile phones and PDA) and the advanced applications (such as contextual web services) the market is seeking for. Adaptation of web contents to various devices (such as standard size screens vs. PDA) and adaptation to various contexts (such as user profile, time, or location) do not differ in the techniques they require. In the following, proposals are made for enhancing existing standards with adaptation capabilities that consist in minimal conservative changes of the existing standards.

      @inproceedings{PMS-FB-2002-3,
              author = {Fran\c{c}ois Bry and Michael Kraus},
              title = {Position Paper: Style Sheets for Context Adaptation},
              booktitle = {Proceedings of W3C Workshop on Delivery Context, Sophia-Antipolis, France (4th--5th March 2002)},
              year = {2002},
              organization = {W3C/INRIA},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-3}
      }
      

The growing importance of XML as a data interchange standard demands languages for data querying and transformation. Since the mid 90es, several such languages have been proposed that are inspired from functional languages (such as XSLT) and/or database query languages (such as XQuery). This paper addresses applying logic programming concepts and techniques to designing a declarative, rule-based query and transformation language for XML and semistructured data. The paper first introduces issues specific to XML and semistructured data such as the necessity of flexible "query terms" and of "construct terms". Then, it is argued that logic programming concepts are particularly appropriate for a declarative query and transformation language for XML and semistructured data. Finally, a new form of unification, called "simulation unification", is proposed for answering "query terms", and it is illustrated on examples.

      @techreport{PMS-FB-2002-2,
              author = {Fran\c{c}ois Bry and Sebastian Schaffert},
              title = {Towards a Declarative Query and Transformation Language for XML and Semistructured Data: Simulation Unification},
              institution = {Institute for Informatics, University of Munich},
              year = {2002},
              type = {Research Report},
              number = {PMS-FB-2002-2},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-2}
      }
      

A simple extension is proposed for enhancing HTML and XML with adaptation. It consists in using the path selectors of style sheet languages such as CSS and XSLT for expressing content and navigation adaptation. The needed extensions to a path selector language are minimal, a few additional constructs suffice. The processor of the language can be kept almost unchanged, no new algorithms are needed. Furthermore, it is proposed to use XML for expressing user model data like browsing history, browsing environment (such as device, time, etc.), and application data (such as user performances on exercises).

      @techreport{PMS-FB-2002-1,
              author = {Fran\c{c}ois Bry and Michael Kraus},
              title = {Adaptive Hypermedia made simple using HTML/XML Style Sheet Selectors},
              institution = {Institute for Informatics, University of Munich},
              year = {2002},
              type = {Research Report},
              number = {PMS-FB-2002-1},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2002-1}
      }
      

Constraint-based programming languages enjoy both elegant theoretical properties and practical success. As it runs, a constraint-based program successively generates pieces of partial information called constraints. The constraint solver has the task to collect, combine, and simplify the constraints, and detect their inconsistency. Intuitively, constraints represent elementary relationships between variables and values, for example equality or some order relationships. Clearly, the abilities and quality of the constraint solver play an essential role in constraint-based programming. In the beginning, constraint solving was "hard-wired" in a built-in constraint solver written in a low-level language, termed the "black-box" approach. While efficient, this approach makes it hard to modify a solver or build a solver over a new domain, let alone reason about and analyze it. As the behavior of the solver can neither be inspected by the user nor explained by the computer, debugging of constraint-based programs is hard. Also, one lesson learned from practical applications is that constraints are often heterogeneous and application specific. Several proposals have been made to allow more flexibility and customization of constraint solvers, often termed "glass-box" approaches. The most far-reaching proposal is the rule-based formalism. In this approach, the constraint propagation is achieved by repeated application of rules. This work aims at covering all aspects of rule-based constraint programming. Going from theory to practice, we will present some analysis and debugging methods for rule-based constraint solvers. Then, we will present a new research area, where users for whom writing constraint solvers remains a hard task have the possibility to do it automatically. The paper then describes an implementation of a Java Constraint Kit consisting of a rule-based language for writing constraint solvers and a generic search engine to solve combinatorial problems. Then, we show how to extend a specific rule-based constraint language to become a general purpose language without losing the extra features supporting efficient constraint solving, e.g. committed choice and matching. Finally, we introduce two applications that benefit from using a rule-based constraint language for writing constraint solvers.

      @phdthesis{PMS-DISS-2001-1,
              author = {Slim Abdennadher},
              title = {Rule-based Constraint Programming: Theory and Practice},
              school = {Institute of Computer Science, LMU, Munich},
              year = {2001},
              note = {Habilitation Thesis, Insitute for Informatics, University of Munich},
              type = {{Habilitationsschrift/habilitation thesis}},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-DISS-2001-1}
      }
      

We are interested in investigating the confluence properties of cooperating constraint solvers. To this end, we model solvers as reductions that transform constraint networks, we define the notion of insensitivity to a superset relation, and show that, if each solver of a given set of solvers is insensitive to the same terminating superset relation, then any combination of these solvers is confluent. By means of this modular approach, we study the relationship between confluence and maintaining certain levels of local consistency and we demonstrate the confluence of a solver for a global finite-domain constraint that consists of several reductions.

      @techreport{PMS-FB-2001-18,
              author = {Michael Marte},
              title = {A Modular Approach To Proving Confluence},
              institution = {Institute for Informatics, University of Munich},
              year = {2001},
              type = {Research Report},
              number = {PMS-FB-2001-18},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2001-18}
      }
      

The location path language XPath is of particular importance for XML applications since it is a core component of many XML processing standards such as XSLT or XQuery. In this paper, based on axis symmetry of XPath, equivalences of XPath 1.0 location paths involving ``reverse axes'', such as ancestor and preceding, are established. These equivalences are used as rewriting rules in an algorithm for transforming location paths with reverse axes into equivalent reverse-axis-free ones. Location paths without reverse axes as generated by the presented rewriting algorithm enable efficient SAX-like streamed data processing of XPath.

      @techreport{PMS-FB-2001-17,
              author = {Dan Olteanu and Holger Meuss and Tim Furche and Fran\c{c}ois Bry},
              title = {XPath: Looking Forward},
              institution = {Institute for Informatics, University of Munich},
              year = {2001},
              type = {Research Report},
              number = {PMS-FB-2001-17},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2001-17}
      }
      

The location path language XPath is of particular importance for XML applications since it is a core component of many XML processing standards such as XSLT or XQuery. In this paper, based on axis symmetry of XPath, equivalences of XPath 1.0 location paths involving ``reverse axes'', such as ancestor and preceding, are established. These equivalences are used as rewriting rules in an algorithm for transforming location paths with reverse axes into equivalent reverse-axis-free ones. Location paths without reverse axes as generated by the presented rewriting algorithm enable efficient SAX-like streamed data processing of XPath.

      @inproceedings{PMS-FB-2001-16,
              author = {Dan Olteanu and Holger Meuss and Tim Furche and Fran\c{c}ois Bry},
              title = {Symmetry in XPath},
              booktitle = {Proceedings of Seminar on Rule Markup Techniques, no. 02061, Schloss Dagstuhl, Germany (7th February 2002)},
              year = {2001},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2001-16}
      }
      

A difficulty that arises frequently when writing a constraint solver is to determine the constraint propagation and simplification algorithm. In previous work, different methods for automatic generation of propagation rules and simplification rules for constraints defined over finite domains have been proposed. In this paper, we present a method for generating rule-based solvers for constraint predicates defined by means of a constraint logic program, even when the constraint domain is infinite. This approach can be seen as a concrete step towards Inductive Constraint Solving.

      @inproceedings{PMS-FB-2001-15,
              author = {Slim Abdennadher and Christophe Rigotti},
              title = {Towards Inductive Constraint Solving},
              booktitle = {Proceedings of Seventh International Conference on Principles and Practice of Constraint Programming, Paphos, Cyprus (26th November--1st December 2001)},
              year = {2001},
              url = {https://www.pms.ifi.lmu.de/publikationen/#PMS-FB-2001-15}
      }