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A User’s Guide to gringo, clasp, clingo, and iclingo
"... This document provides an introduction to the Answer Set Programming (ASP) tools gringo, clasp, clingo, and iclingo, developed at the University of Potsdam. The first tool, gringo, is a grounder capable of translating logic programs provided by users into equivalent propositional logic programs. Th ..."
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This document provides an introduction to the Answer Set Programming (ASP) tools gringo, clasp, clingo, and iclingo, developed at the University of Potsdam. The first tool, gringo, is a grounder capable of translating logic programs provided by users into equivalent propositional logic programs. The answer sets of such programs can be computed by clasp, which is a solver. The third tool, clingo, integrates the functionalities of gringo and clasp, thus, acting as a monolithic solver for user programs. Finally, iclingo extends clingo by an incremental mode that incorporates both grounding and solving. For one, this document aims at enabling ASP novices to make use of the aforementioned tools. For another, it provides a reference of their features that ASP adepts might be tempted to exploit. Note that this document contains a lot of examples. For convienience no examples have to be typed in by hand instead they can directly be safed to disc by clicking them.
Modularity Aspects of Disjunctive Stable Models
, 2007
"... Practically all programming languages used in software engineering allow to split a program into several modules. For fully declarative and nonmonotonic logic programming languages, however, the modular structure of programs is hard to realise, since the output of an entire program cannot in general ..."
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Cited by 30 (8 self)
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Practically all programming languages used in software engineering allow to split a program into several modules. For fully declarative and nonmonotonic logic programming languages, however, the modular structure of programs is hard to realise, since the output of an entire program cannot in general be composed from the output of its component programs in a direct manner. In this paper, we consider these aspects for the stablemodel semantics of disjunctive logic programs (DLPs). We define the notion of a DLPfunction, where a welldefined input/output interface is provided, and establish a novel module theorem enabling a suitable compositional semantics for modules. The module theorem extends the wellknown splittingset theorem and allows also a generalisation of a shifting technique for splitting shared disjunctive rules among components.
The ConflictDriven Answer Set Solver clasp: Progress Report
"... Abstract. We summarize the salient features of the current version of the answer set solver clasp, focusing on the progress made since version RC4 of clasp. Apart from enhanced preprocessing and searchsupporting techniques, a particular emphasis lies on advanced reasoning modes, such as cautious an ..."
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Abstract. We summarize the salient features of the current version of the answer set solver clasp, focusing on the progress made since version RC4 of clasp. Apart from enhanced preprocessing and searchsupporting techniques, a particular emphasis lies on advanced reasoning modes, such as cautious and brave reasoning, optimization, solution projection, and incremental solving. 1
Detecting Inconsistencies in Large Biological Networks with Answer Set Programming
, 2008
"... We introduce an approach to detecting inconsistencies in large biological networks by using Answer Set Programming. To this end, we build upon a recently proposed notion of consistency between biochemical/genetic reactions and highthroughput profiles of cell activity. We then present an approach ba ..."
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We introduce an approach to detecting inconsistencies in large biological networks by using Answer Set Programming. To this end, we build upon a recently proposed notion of consistency between biochemical/genetic reactions and highthroughput profiles of cell activity. We then present an approach based on Answer Set Programming to check the consistency of largescale data sets. Moreover, we extend this methodology to provide explanations for inconsistencies in the data by determining minimal representations of conflicts. In practice, this can be used to identify unreliable data or to indicate missing reactions.
ConflictDriven Answer Set Solving: From Theory to Practice
, 2012
"... 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 constraintbased framework capt ..."
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Cited by 11 (1 self)
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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 constraintbased 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 fullfledged algorithmic framework for native conflictdriven 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.
On the Implementation of Weight Constraint Rules in ConflictDriven ASP Solvers
"... Abstract. We present the first comprehensive approach to integrating cardinality and weight rules into conflictdriven ASP solving. We begin with a uniform, constraintbased characterization of answer sets in terms of nogoods. This provides the semantic underpinnings of our approach in fixing all ne ..."
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Cited by 7 (4 self)
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Abstract. We present the first comprehensive approach to integrating cardinality and weight rules into conflictdriven ASP solving. We begin with a uniform, constraintbased characterization of answer sets in terms of nogoods. This provides the semantic underpinnings of our approach in fixing all necessary inferences that must be supported by an appropriate implementation. We then provide key algorithms detailing the salient features needed for implementing weight constraint rules. This involves a sophisticated unfounded set checker as well as an extended propagation algorithm along with the underlying data structures. We implemented our techniques within the ASP solver clasp and demonstrate their effectiveness by an experimental evaluation. 1
Computing Loops with at Most One External Support Rule for Disjunctive Logic Programs
"... Abstract. We extend to disjunctive logic programs our previous work on computing loop formulas of loops with at most one external support. We show that for these logic programs, loop formulas of loops with no external support can be computed in polynomial time, and if the given program has no constr ..."
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Abstract. We extend to disjunctive logic programs our previous work on computing loop formulas of loops with at most one external support. We show that for these logic programs, loop formulas of loops with no external support can be computed in polynomial time, and if the given program has no constraints, an iterative procedure based on these formulas, the program completion, and unit propagation computes the least fixed point of a simplification operator used by DLV. We also relate loops with no external supports to the unfounded sets and the wellfounded semantics of disjunctive logic programs by Wang and Zhou. However, the problem of computing loop formulas of loops with at most one external support rule is NPhard for disjunctive logic programs. We thus propose a polynomial algorithm for computing some of these loop formulas, and show experimentally that this polynomial approximation algorithm can be effective in practice. 1
Exploiting Unfounded Sets for HEXProgram Evaluation
 13th European Conference on Logics in Artificial Intelligence (JELIA 2012), September 2628, 2012
"... Abstract. HEX programs extend logic programs with external computations through external atoms, whose answer sets are the minimal models of the FaberLeonePfeiferreduct. As already reasoning from Horn programs with nonmonotonic external atoms of polynomial complexity is on the second level of the ..."
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Abstract. HEX programs extend logic programs with external computations through external atoms, whose answer sets are the minimal models of the FaberLeonePfeiferreduct. As already reasoning from Horn programs with nonmonotonic external atoms of polynomial complexity is on the second level of the polynomial hierarchy, answer set checking needs special attention; simply computing reducts and searching for smaller models does not scale well. We thus extend an approach based on unfounded sets to HEX and integrate it in a Conflict Driven Clause Learning framework for HEX program evaluation. It reduces the check to a search for unfounded sets, which is more efficiently implemented as a SAT problem. We give a basic encoding for HEX and show optimizations by additional clauses. Experiments show that the new approach significantly decreases runtime.
ComplexitySensitive Decision Procedures for Abstract Argumentation
, 2012
"... Abstract argumentation frameworks (AFs) provide the basis for various reasoning problems in the areas of Knowledge Representation and Artificial Intelligence. Efficient evaluation of AFs has thus been identified as an important research challenge. So far, implemented systems for evaluating AFs have ..."
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Abstract argumentation frameworks (AFs) provide the basis for various reasoning problems in the areas of Knowledge Representation and Artificial Intelligence. Efficient evaluation of AFs has thus been identified as an important research challenge. So far, implemented systems for evaluating AFs have either followed a straightforward reductionbased approach or been limited to certain tractable classes of AFs. In this work, we present a generic approach for reasoning over AFs, based on the novel concept of complexitysensitivity. Establishing the theoretical foundations of this approach, we derive several new complexity results for preferred, semistable and stage semantics which complement the current complexity landscape for abstract argumentation, providing further understanding on the sources of intractability of AF reasoning problems. The introduced generic framework exploits decision procedures for problems of lower complexity whenever possible. This allows, in particular, instantiations of the generic framework via harnessing in an iterative way current sophisticated Boolean satisfiability (SAT) solver technology for solving the considered AF reasoning problems. First experimental results show that the SATbased instantiation of our novel approach outperforms existing systems.
The BioASP Library: ASP Solutions for Systems Biology
"... Abstract—Today’s molecular biology is confronted with enormous amounts of data, generated by new highthroughput technologies, along with an increasing number of biological models available over web repositories. This poses new challenges for bioinformatics to invent methods coping with incompletene ..."
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Abstract—Today’s molecular biology is confronted with enormous amounts of data, generated by new highthroughput technologies, along with an increasing number of biological models available over web repositories. This poses new challenges for bioinformatics to invent methods coping with incompleteness, heterogeneity, and mutual inconsistency of data and models. To this end, we built the library BioASP, providing a framework for analyzing biological data and models with Answer Set Programming (ASP). Due to the expressive modeling language, the inherent tolerance of incomplete knowledge, and efficient solving engines, ASP has proven to be an excellent tool for solving a variety of biological questions. The BioASP library implements methods for analyzing metabolic and gene regulatory networks, consistency checking, diagnosing, and repairing biological data and models. In particular, it allows for computing predictions and generating hypotheses about required expansions of biological models. To accomplish this, expert knowledge of both the biological application and the ASP paradigm needs to be combined. In fact, the functionalities provided by the BioASP library exploit technical knowhow of modeling (biological) problems in ASP and gearing ASP solvers ’ parameters to them. Often, such bestpractice technology is the result of an exhaustive series of tests. The BioASP library integrates our practical experience and offers them via easytouse Python functions, thus enabling ASP nonexperts to solve biological questions with ASP. I.