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Dagstuhl Seminar 05171

Nonmonotonic Reasoning, Answer Set Programming and Constraints

( Apr 24 – Apr 29, 2005 )

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The seminar took place from April 24 to 29, 2005. It was organized by Gerhard Brewka (Univ. Leipzig, DE), Ilkka Niemelä (Helsinki Univ. of Technology, FI), Torsten Schaub (Univ. Potsdam, DE), and Miroslaw Truszczynski (Univ. of Kentucky, US). The seminar was attended by 58 participants from Europe, North America, Asia and Australia.

The technical program consisted of

  • Three invited talks:
    Tomi Janhunen: Translating NLPs into Propositional Theories
    Thomas Eiter: Extending Answer Set Programming for the Semantic Web
    David Mitchell: Progress and Problems in SAT Solving
  • 38 contributed talks given by the participants
  • Panel discussion on the future of the answer-set programming. The panel was mod- erated by Ilkka Niemelä. Marc Denecker, Yannis Dimopoulos, Michael Gelfond and Nicola Leone were panelists.
  • Special session on the benchmarking system asparagus led by Christian Anger and Miroslaw Truszczynski

The technical program of the seminar demonstrated that since our first meeting in Dagstuhl in September 2002, substantial scientific progress has been achieved in several areas:

  • Theory of answer-set programming . Much progress has been obtained in understanding encodings of programs as propositional theories through research on the concepts of completion and loop formula. Logic programming with nested expressions and logic of here-and-there and its relatives solidified their position as fundamental formalisms for the development of the theory of answer-set programming. Other notable developments include ID-logic, which expands classical logic with inductive definitions represented as a logic programs, new results on program equivalence and proof systems for programs with cardinality constraints.
  • Software for answer-set programming . Dlv emerged as an "almost" production- grade package of answer-set programming tools supporting program grounding, answer- set computation and integration with database environments. Several new solvers were introduced: cmodels enhanced to handle disjunctive programs, pbmodels , which uses pseudo-boolean solvers to compute stable models of programs with weight atoms, and nomore++ - a system implementing new branching and propagation techniques. Asparagus, an environment for systematic and objective testing of answer-set solvers has grown and matured significantly since it was first proposed at the Dagstuhl Seminar 02381 in September 2002. Researchers also have been investigating and developing tools for distributed processing of answer-set programs (Platypus project). Finally, the workshop presented research on program development tools supporting static program analysis and debugging.
  • Applications . The seminar demonstrated that answer-set programming becomes a viable software tool in several application domains including: semantic web, data integration, systems of boolean equations, planning, security engineering, social modeling, and qualitative decision theory.
  • Strong connections to propositional satisfiability . It has been clear for quite some time that our field can benefit from closer collaboration with researchers in the SAT community. This seminar had several talks that emphasized that connection, most notably the invited talk by David Mitchell, which will undoubtedly have major impact on the development and implementation of new answer-set programming solvers.

General conclusions from the seminar are very positive. The seminar was dominated by young researchers and students, about 25 of whom delivered presentations. Our community is branching out to related communities of propositional satisfiability and constraint satisfaction, both theory and software development are actively pursued, and there is a strong push towards practical applications.

  • Juan Acosta Guadarrama (TU Clausthal, DE)
  • Christian Anger (Universität Potsdam, DE)
  • Martin Brain (University of Bath, GB) [dblp]
  • Loreto Bravo (Carleton University - Ottawa, CA)
  • Gerhard Brewka (Universität Leipzig, DE) [dblp]
  • Stefania Costantini (University of L'Aquila, IT)
  • Marina De Vos (University of Bath, GB)
  • Marc Denecker (KU Leuven, BE) [dblp]
  • Yannis Dimopoulos (University of Cyprus, CY)
  • Jürgen Dix (TU Clausthal, DE) [dblp]
  • Thomas Eiter (TU Wien, AT) [dblp]
  • Esra Erdem (TU Wien, AT) [dblp]
  • Wolfgang Faber (University of Calabria, IT)
  • Paolo Ferraris (University of Texas - Austin, US)
  • Martin Gebser (Universität Potsdam, DE)
  • Michael Gelfond (Texas Tech University - Lubbock, US)
  • Rafal Grabos (Universität Leipzig, DE)
  • Stijn Heymans (Free University of Brussels, BE)
  • Giovambattista Ianni (TU Wien, AT)
  • Tomi Janhunen (Helsinki University of Technology, FI)
  • Gabriele Kern-Isberner (TU Dortmund, DE) [dblp]
  • Kathrin Konczak (Universität Potsdam, DE)
  • Joohyung Lee (University of Texas - Austin, US)
  • Nicola Leone (University of Calabria, IT) [dblp]
  • Yuliya Lierler (Universität Erlangen-Nürnberg, DE)
  • Marco Maratea (University of Genova, IT)
  • Victor W. Marek (University of Kentucky - Lexington, US)
  • Maarten Marien (KU Leuven, BE)
  • Fabio Massacci (Università di Trento, IT) [dblp]
  • Robert Mercer (University of Western Ontario - London, CA) [dblp]
  • Artur Mikitiuk (Univ. of Texas at Tyler, US)
  • Alessandra Mileo (University of Milan, IT) [dblp]
  • David Mitchell (Simon Fraser University - Burnaby, CA)
  • Rudradeb Mitra (KU Leuven, BE)
  • Pascal Nicolas (Université d'Angers, FR)
  • Ilkka Niemelä (Helsinki University of Technology, FI)
  • Peter Novák (TU Clausthal, DE) [dblp]
  • Emilia Oikarinen (Helsinki University of Technology, FI)
  • Ramon P. Otero (University of La Coruña, ES)
  • David J. Pearce (Universidad Rey Juan Carlos - Madrid, ES) [dblp]
  • Inna Pivkina (New Mexico State University, US)
  • Axel Polleres (Universität Innsbruck, AT) [dblp]
  • Alessandro Provetti (Università di Messina, IT) [dblp]
  • Jeffrey Remmel (University of California - San Diego, US)
  • Orkunt Sabuncu (Middle East Technical University - Ankara, TR)
  • Ken Satoh (National Institute of Informatics - Tokyo, JP) [dblp]
  • Torsten Schaub (Universität Potsdam, DE) [dblp]
  • John Schlipf (University of Cincinnati, US)
  • Tommi Syrjänen (Helsinki University of Technology, FI)
  • Eugenia Ternovska (Simon Fraser University - Burnaby, CA) [dblp]
  • Hans Tompits (TU Wien, AT)
  • Miroslaw Truszczynski (University of Kentucky - Lexington, US) [dblp]
  • Agustin Valverde Ramos (University of Malaga, ES)
  • Davy Van Nieuwenborgh (Free University of Brussels, BE)
  • Joost Vennekens (KU Leuven, BE)
  • Kewen Wang (Griffith University - Brisbane, AU)
  • Stefan Woltran (TU Wien, AT) [dblp]
  • Yuting Zhao (Centro Ricerche FIAT - Trento, IT)