Answer-set programming (ASP) has become an important paradigm for declarative problem solving in recent years. However, to further improve the usability of answer-set programs, the development of software-engineering ...
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ISBN:
(纸本)9783540721994
Answer-set programming (ASP) has become an important paradigm for declarative problem solving in recent years. However, to further improve the usability of answer-set programs, the development of software-engineering tools is vital. In particular, the area of debugging provides a challenge in boththeoretical and practical terms. this is due to the purely declarative nature of ASP that, on the one hand, calls for solver-independent methodologies and, on the other hand, does not directly apply to tracing techniques. In this paper, we propose a novel methodology, which rests within ASP itself, to sort out errors on the conceptual level. Our method makes use of tagging, where the program to be analyzed is rewritten using dedicated control atoms. this provides a flexible way to specify different types of debugging requests and a first step towards a dedicated (meta level) debugging language.
acthex programs are a convenient tool for connecting stateful external environments to logic programs. In the acthex framework, actual actions on an external environment can be declaratively selected, rearranged, sche...
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ISBN:
(纸本)9783642405648
acthex programs are a convenient tool for connecting stateful external environments to logic programs. In the acthex framework, actual actions on an external environment can be declaratively selected, rearranged, scheduled and then executed depending on intelligence specified in an ASP-based language. We report in this paper about recent improvements of the formal and of the operational acthex programming framework. Besides yielding a significant increase in versatility of the framework, we also present illustrative application showcases and a short evaluation thereof exhibiting computational acthex strengths.
In this paper, we define and investigate the complexity of several nonmonotoniclogics with quantified Boolean formulas as constraints. We give quantified constraint versions of the constraint programming formalism of...
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Answer set programming (ASP) features a rich rule-based modeling language for encoding search problems. While normal rules form the simplest rule type in the language, various forms of extended rules have been introdu...
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ISBN:
(纸本)9783319616605;9783319616599
Answer set programming (ASP) features a rich rule-based modeling language for encoding search problems. While normal rules form the simplest rule type in the language, various forms of extended rules have been introduced in order to ease modeling of complex conditions and constraints. Normalization means replacing such extended rules with identically functioning sets of normal rules. In this system description, we present LP2NORMAL, which is a state-of-the-art normalizer that acts as a filter on ground logic programs produced by grounders, such as gringo. It provides options to translate away choice rules, cardinality rules, and weight rules, and to rewrite optimization statements using comparable techniques. the produced logic programs are suitable inputs to tools that lack support for extended rules, in particular. We give an overview of the normalization techniques currently supported by the tool and summarize its features. Moreover, we discuss the typical application scenarios of normalization, such as when implementing the search for answer sets using a back-end solver without direct support for cardinality constraints or pseudo-Boolean constraints.
Competitive native solvers for Answer Set programming (ASP) perform a backtracking search by assuming the truth of literals. the choice of literals (the heuristic) is fundamental for the performance of these systems. ...
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ISBN:
(纸本)9783540721994
Competitive native solvers for Answer Set programming (ASP) perform a backtracking search by assuming the truth of literals. the choice of literals (the heuristic) is fundamental for the performance of these systems. Most of the efficient ASP systems employ a heuristic based on look-ahead, that is, a literal is tentatively assumed and its heuristic value is based on its deterministic consequences. However, looking ahead is a costly operation, and indeed look-ahead often accounts for the majority of time taken by ASP solvers. For Satisfiability (SAT), a radically different approach, called look-back heuristic, proved to be quite successful: Instead of looking ahead, one uses information gathered during the computation performed so far, thus looking back. In this approach, atoms which have been frequently involved in inconsistencies are preferred. In this paper, we carry over this approach to the framework of disjunctive ASP. We design a number of look-back heuristics exploiting peculiarities of ASP and implement them in the ASP system DLV. We compare their performance on a collection of hard ASP programs both structured and randomly generated. these experiments indicate that a very basic approach works well, outperforming all of the prominent disjunctive ASP systems - DLV (with its traditional heuristic), GnT, and CModels3 - on many of the instances considered.
To ensure a close relation between the answer sets of a program and those of its ground version, some answer set solvers deal with variables by requiring a safety condition on program rules. If we go beyond the syntax...
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ISBN:
(纸本)9783642042379
To ensure a close relation between the answer sets of a program and those of its ground version, some answer set solvers deal with variables by requiring a safety condition on program rules. If we go beyond the syntax of disjunctive programs, for instance by allowing rules with nested expressions, or perhaps even arbitrary first-order formulas, new definitions of safety are required. In this paper we consider a new concept of safety for formulas in quantified equilibrium logic where answer sets can be defined for arbitrary first-order formulas. the new concept captures and generalises two recently proposed safety definitions: that of Lee, Lifschitz and Palla (2008) as well as that of Bria, Faber and Leone (2008). We Study the main metalogical properties of safe formulas.
Prioritized logic programs (PLPs) have a mechanism of representing priority knowledge in logic programs. the declarative semantics of a PLP is given as preferred answer sets which are used for representing nonmonotoni...
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ISBN:
(数字)9783540398134
ISBN:
(纸本)3540201017
Prioritized logic programs (PLPs) have a mechanism of representing priority knowledge in logic programs. the declarative semantics of a PLP is given as preferred answer sets which are used for representing nonmonotonicreasoning as well as preference abduction. From the computational viewpoint, however, its implementation issues have little been studied and no sound procedure is known for computing preferred answer sets of PLPs. In this paper, we present a sound and complete procedure to compute all preferred answer sets of a PLP in answer set programming. the procedure is based on a program transformation from a PLP to a logic program and is realized on top of any procedure for answer set programming. the proposed technique also extends PLPs to handle dynamic preference and we address its application to legal reasoning.
In this paper we study the relation between the two main extensions of Answer Set programming with temporal modal operators: Temporal Equilibrium logic (TEL) and Temporal Answer Sets (TAS). On the one hand, TEL is a c...
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ISBN:
(纸本)9783642405648
In this paper we study the relation between the two main extensions of Answer Set programming with temporal modal operators: Temporal Equilibrium logic (TEL) and Temporal Answer Sets (TAS). On the one hand, TEL is a complete non-monotonic logicthat results from the combination of Linear-time Temporal logic (LTL) with Equilibrium logic. On the other hand, TAS is based on a richer modal approach, Dynamic LTL (DLTL), whereas its non-monotonic part relies on a reduct-based definition for a particular limited syntax. To integrate both approaches, we propose a Dynamic Linear-time extension of Equilibrium logic (DTEL) that allows accommodating both TEL and TAS as particular cases. With respect to TEL, DTEL incorporates more expressiveness thanks to the addition of dynamic logic operators, whereas with respect to TAS, DTEL provides a complete non-monotonic semantics applicable to arbitrary theories. In the paper, we identify cases in which both formalisms coincide and explain how this relation can be exploited for adapting existing TEL and TAS computation methods to the general case of DTEL.
In answer-set programming (ASP), many notions of program equivalence have been introduced and formally analysed. A particular line of research in this direction aims at studying conditions under which certain syntacti...
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ISBN:
(纸本)9783642042379
In answer-set programming (ASP), many notions of program equivalence have been introduced and formally analysed. A particular line of research in this direction aims at studying conditions under which certain syntactic constructs can be eliminated from programs preserving some given equivalence relation. In this paper, we continue this endeavour introducing novel conditions under which disjunction and negation can be eliminated from answer-set programs under relativised strong equivalence with projection. this notion is a generalisation of the usual strong-equivalence relation, as introduced by Lifschitz. Pearce, and Valverde, by allowing parametrisable context and Output alphabets, which is an important feature in view of practical programming techniques like the use of local variables and modules. We provide model-theoretic conditions that hold for a disjunctive logic program P precisely when there is a program Q, equivalent to P under our considered notion, Such that Q is either positive, normal, or Horn, respectively. Moreover, we outline how such a Q, called a casting of P, can be obtained, and consider complexity issues.
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