TY - JOUR A1 - Anger, Christian A1 - Gebser, Martin A1 - Janhunen, Tomi A1 - Schaub, Torsten H. T1 - What's a head without a body? Y1 - 2006 ER - TY - JOUR A1 - Anger, Christian A1 - Gebser, Martin A1 - Linke, Thomas A1 - Neumann, Andre A1 - Schaub, Torsten H. T1 - The nomore++ approach to answer set solving Y1 - 2005 UR - http://www.cs.uni-potsdam.de/wv/pdfformat/angelinesc05c.pdf ER - TY - JOUR A1 - Anger, Christian A1 - Gebser, Martin A1 - Linke, Thomas A1 - Neumann, Andre A1 - Schaub, Torsten H. T1 - The nomore++ approach to answer set solving Y1 - 2005 UR - http://www.cs.uni-potsdam.de/wv/pdfformat/angelinesc05c.pdf ER - TY - JOUR A1 - Anger, Christian A1 - Gebser, Martin A1 - Schaub, Torsten H. T1 - Approaching the core of unfounded sets Y1 - 2006 UR - http://www.cs.uni-potsdam.de/wv/pdfformat/angesc06a.pdf ER - TY - JOUR A1 - Brain, Martin A1 - Gebser, Martin A1 - Pührer, Jörg A1 - Schaub, Torsten H. A1 - Tompits, Hans A1 - Woltran, Stefan T1 - "That is illogical, Captain!" : the debugging support tool spock for answer-set programs ; system description Y1 - 2007 ER - TY - JOUR A1 - Brain, Martin A1 - Gebser, Martin A1 - Pührer, Jörg A1 - Schaub, Torsten H. A1 - Tompits, Hans A1 - Woltran, Stefan T1 - Debugging ASP programs by means of ASP Y1 - 2007 SN - 978-3-540- 72199-4 ER - TY - JOUR A1 - Dimopoulos, Yannis A1 - Gebser, Martin A1 - Lühne, Patrick A1 - Romero Davila, Javier A1 - Schaub, Torsten H. T1 - plasp 3 BT - Towards Effective ASP Planning JF - Theory and practice of logic programming N2 - We describe the new version of the Planning Domain Definition Language (PDDL)-to-Answer Set Programming (ASP) translator plasp. First, it widens the range of accepted PDDL features. Second, it contains novel planning encodings, some inspired by Satisfiability Testing (SAT) planning and others exploiting ASP features such as well-foundedness. All of them are designed for handling multivalued fluents in order to capture both PDDL as well as SAS planning formats. Third, enabled by multishot ASP solving, it offers advanced planning algorithms also borrowed from SAT planning. As a result, plasp provides us with an ASP-based framework for studying a variety of planning techniques in a uniform setting. Finally, we demonstrate in an empirical analysis that these techniques have a significant impact on the performance of ASP planning. KW - knowledge representation and nonmonotonic reasoning KW - technical notes and rapid communications KW - answer set programming KW - automated planning KW - action and change Y1 - 2019 U6 - https://doi.org/10.1017/S1471068418000583 SN - 1471-0684 SN - 1475-3081 VL - 19 IS - 3 SP - 477 EP - 504 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Gebser, Martin A1 - Gharib, Mona A1 - Mercer, Robert E. A1 - Schaub, Torsten H. T1 - Monotonic answer set programming N2 - Answer set programming (ASP) does not allow for incrementally constructing answer sets or locally validating constructions like proofs by only looking at a part of the given program. In this article, we elaborate upon an alternative approach to ASP that allows for incremental constructions. Our approach draws its basic intuitions from the area of default logics. We investigate the feasibility of the concept of semi-monotonicity known from default logics as a basis of incrementality. On the one hand, every logic program has at least one answer set in our alternative setting, which moreover can be constructed incrementally based on generating rules. On the other hand, the approach may produce answer sets lacking characteristic properties of standard answer sets, such as being a model of the given program. We show how integrity constraints can be used to re-establish such properties, even up to correspondence with standard answer sets. Furthermore, we develop an SLD-like proof procedure for our incremental approach to ASP, which allows for query-oriented computations. Also, we provide a characterization of our definition of answer sets via a modification of Clarks completion. Based on this notion of program completion, we present an algorithm for computing the answer sets of a logic program in our approach. Y1 - 2009 UR - http://logcom.oxfordjournals.org/ U6 - https://doi.org/10.1093/logcom/exn040 SN - 0955-792X ER - TY - JOUR A1 - Gebser, Martin A1 - Gharib, Mona A1 - Schaub, Torsten H. T1 - Incremental answer sets and their computation Y1 - 2007 ER - TY - JOUR A1 - Gebser, Martin A1 - Janhunen, Tomi A1 - Rintanen, Jussi T1 - Declarative encodings of acyclicity properties JF - Journal of logic and computation N2 - Many knowledge representation tasks involve trees or similar structures as abstract datatypes. However, devising compact and efficient declarative representations of such structural properties is non-obvious and can be challenging indeed. In this article, we take a number of acyclicity properties into consideration and investigate various logic-based approaches to encode them. We use answer set programming as the primary representation language but also consider mappings to related formalisms, such as propositional logic, difference logic and linear programming. We study the compactness of encodings and the resulting computational performance on benchmarks involving acyclic or tree structures. KW - acyclicity properties KW - logic-based modeling KW - answer set programming KW - satisfiability Y1 - 2015 U6 - https://doi.org/10.1093/logcom/exv063 SN - 0955-792X SN - 1465-363X VL - 30 IS - 4 SP - 923 EP - 952 PB - Oxford Univ. Press CY - Eynsham, Oxford ER - TY - JOUR A1 - Gebser, Martin A1 - Kaminski, Roland A1 - Kaufmann, Benjamin A1 - Lühne, Patrick A1 - Obermeier, Philipp A1 - Ostrowski, Max A1 - Romero Davila, Javier A1 - Schaub, Torsten H. A1 - Schellhorn, Sebastian A1 - Wanko, Philipp T1 - The Potsdam Answer Set Solving Collection 5.0 JF - Künstliche Intelligenz N2 - The Potsdam answer set solving collection, or Potassco for short, bundles various tools implementing and/or applying answer set programming. The article at hand succeeds an earlier description of the Potassco project published in Gebser et al. (AI Commun 24(2):107-124, 2011). Hence, we concentrate in what follows on the major features of the most recent, fifth generation of the ASP system clingo and highlight some recent resulting application systems. Y1 - 2018 U6 - https://doi.org/10.1007/s13218-018-0528-x SN - 0933-1875 SN - 1610-1987 VL - 32 IS - 2-3 SP - 181 EP - 182 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Gebser, Martin A1 - Kaminski, Roland A1 - Schaub, Torsten H. T1 - Complex optimization in answer set programming JF - Theory and practice of logic programming N2 - Preference handling and optimization are indispensable means for addressing nontrivial applications in Answer Set Programming (ASP). However, their implementation becomes difficult whenever they bring about a significant increase in computational complexity. As a consequence, existing ASP systems do not offer complex optimization capacities, supporting, for instance, inclusion-based minimization or Pareto efficiency. Rather, such complex criteria are typically addressed by resorting to dedicated modeling techniques, like saturation. Unlike the ease of common ASP modeling, however, these techniques are rather involved and hardly usable by ASP laymen. We address this problem by developing a general implementation technique by means of meta-prpogramming, thus reusing existing ASP systems to capture various forms of qualitative preferences among answer sets. In this way, complex preferences and optimization capacities become readily available for ASP applications. KW - Answer Set Programming KW - Preference Handling KW - Complex optimization KW - Meta-Programming Y1 - 2011 U6 - https://doi.org/10.1017/S1471068411000329 SN - 1471-0684 VL - 11 IS - 3 SP - 821 EP - 839 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Gebser, Martin A1 - Kaufmann, Benjamin A1 - Kaminski, Roland A1 - Ostrowski, Max A1 - Schaub, Torsten H. A1 - Schneider, Marius T1 - Potassco the Potsdam answer set solving collection JF - AI communications : AICOM ; the European journal on artificial intelligence N2 - This paper gives an overview of the open source project Potassco, the Potsdam Answer Set Solving Collection, bundling tools for Answer Set Programming developed at the University of Potsdam. KW - Answer set programming KW - declarative problem solving Y1 - 2011 U6 - https://doi.org/10.3233/AIC-2011-0491 SN - 0921-7126 VL - 24 IS - 2 SP - 107 EP - 124 PB - IOS Press CY - Amsterdam ER - TY - JOUR A1 - Gebser, Martin A1 - Kaufmann, Benjamin A1 - Neumann, André A1 - Schaub, Torsten H. T1 - Conflict-driven answer set enumeration Y1 - 2007 SN - 978-3-540- 72199-4 ER - TY - JOUR A1 - Gebser, Martin A1 - Kaufmann, Benjamin A1 - Neumann, André A1 - Schaub, Torsten H. T1 - Conflict-driven answer set solving Y1 - 2007 SN - 978-1-57735-323-2 ER - TY - JOUR A1 - Gebser, Martin A1 - Kaufmann, Benjamin A1 - Neumann, André A1 - Schaub, Torsten H. T1 - Clasp : a conflict-driven answer set solver Y1 - 2007 SN - 978-3-540- 72199-4 ER - TY - JOUR A1 - Gebser, Martin A1 - Kaufmann, Benjamin A1 - Schaub, Torsten H. T1 - Conflict-driven answer set solving: From theory to practice JF - Artificial intelligence N2 - We introduce an approach to computing answer sets of logic programs, based on concepts successfully applied in Satisfiability (SAT) checking. The idea is to view inferences in Answer Set Programming (ASP) as unit propagation on nogoods. This provides us with a uniform constraint-based framework capturing diverse inferences encountered in ASP solving. Moreover, our approach allows us to apply advanced solving techniques from the area of SAT. As a result, we present the first full-fledged algorithmic framework for native conflict-driven ASP solving. Our approach is implemented in the ASP solver clasp that has demonstrated its competitiveness and versatility by winning first places at various solver contests. KW - Answer set programming KW - Logic programming KW - Nonmonotonic reasoning Y1 - 2012 U6 - https://doi.org/10.1016/j.artint.2012.04.001 SN - 0004-3702 VL - 187 IS - 8 SP - 52 EP - 89 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Gebser, Martin A1 - Kaufmann, Benjamin A1 - Schaub, Torsten H. T1 - Multi-threaded ASP solving with clasp JF - Theory and practice of logic programming N2 - We present the new multi-threaded version of the state-of-the-art answer set solver clasp. We detail its component and communication architecture and illustrate how they support the principal functionalities of clasp. Also, we provide some insights into the data representation used for different constraint types handled by clasp. All this is accompanied by an extensive experimental analysis of the major features related to multi-threading in clasp. Y1 - 2012 U6 - https://doi.org/10.1017/S1471068412000166 SN - 1471-0684 VL - 12 IS - 8 SP - 525 EP - 545 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Gebser, Martin A1 - Lee, Joohyung A1 - Lierler, Yuliya T1 - Head-elementary-set-free logic programs Y1 - 2007 SN - 978-3-540- 72199-4 ER - TY - JOUR A1 - Gebser, Martin A1 - Lee, Joohyung A1 - Lierler, Yuliya T1 - On elementary loops of logic programs JF - Theory and practice of logic programming N2 - Using the notion of an elementary loop, Gebser and Schaub (2005. Proceedings of the Eighth International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMR'05), 53-65) refined the theorem on loop formulas attributable to Lin and Zhao (2004) by considering loop formulas of elementary loops only. In this paper, we reformulate the definition of an elementary loop, extend it to disjunctive programs, and study several properties of elementary loops, including how maximal elementary loops are related to minimal unfounded sets. The results provide useful insights into the stable model semantics in terms of elementary loops. For a nondisjunctive program, using a graph-theoretic characterization of an elementary loop, we show that the problem of recognizing an elementary loop is tractable. On the other hand, we also show that the corresponding problem is coNP-complete for a disjunctive program. Based on the notion of an elementary loop, we present the class of Head-Elementary-loop-Free (HEF) programs, which strictly generalizes the class of Head-Cycle-Free (HCF) programs attributable to Ben-Eliyahu and Dechter (1994. Annals of Mathematics and Artificial Intelligence 12, 53-87). Like an Ha: program, an HEF program can be turned into an equivalent nondisjunctive program in polynomial time by shifting head atoms into the body. KW - stable model semantics KW - loop formulas KW - unfounded sets Y1 - 2011 U6 - https://doi.org/10.1017/S1471068411000019 SN - 1471-0684 VL - 11 IS - 2 SP - 953 EP - 988 PB - Cambridge Univ. Press CY - New York ER -