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Loop-separable programs and their first-order definability

ARTIFICIAL INTELLIGENCE 2011年第3-4期175卷 890-913页

作者： Chen, Yin Lin, Fangzhen Zhang, Yan Zhou, Yi S China Normal Univ Dept Comp Sci Guangzhou Guangdong Peoples R China Hong Kong Univ Sci & Technol Dept Comp Sci Kowloon Hong Kong Peoples R China Univ Western Sydney Intelligent Syst Lab Sch Comp & Math Penrith NSW 1797 Australia

An answer set program with variables is first-order definable on finite structures if the set of its finite answer sets can be captured by a first-order sentence. Characterizing classes of programs that are first-order definable on finite structures is theoretically challenging and of practical relevance to answer set programming. In this paper, we identify a non-trivial class of answer set programs called loop-separable programs and show that they are first-order definable on finite structures. (C) 2010 Elsevier B.V. All rights reserved.

关键词： answer set programming First-order definability Knowledge representation Nonmonotonic reasoning

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Magic sets for disjunctive Datalog programs

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ARTIFICIAL INTELLIGENCE 2012年 187卷 156-192页

作者： Alviano, Mario Faber, Wolfgang Greco, Gianluigi Leone, Nicola Univ Calabria Dept Math I-87036 Arcavacata Di Rende Italy

In this paper, a new technique for the optimization of (partially) bound queries over disjunctive Datalog programs with stratified negation is presented. The technique exploits the propagation of query bindings and extends the Magic set optimization technique (originally defined for non-disjunctive programs). An important feature of disjunctive Datalog programs is non-monotonicity, which calls for non-deterministic implementations, such as backtracking search. A distinguishing characteristic of the new method is that the optimization can be exploited also during the non-deterministic phase. In particular, after some assumptions have been made during the computation, parts of the program may become irrelevant to a query under these assumptions. This allows for dynamic pruning of the search space. In contrast, the effect of the previously defined Magic set methods for disjunctive Datalog is limited to the deterministic portion of the process. In this way, the potential performance gain by using the proposed method can be exponential, as could be observed empirically. The correctness of the method is established and proved in a formal way thanks to a strong relationship between Magic sets and unfounded sets that has not been studied in the literature before. This knowledge allows for extending the method and the correctness proof also to programs with stratified negation in a natural way. The proposed method has been implemented in the DLV system and various experiments on synthetic as well as on real-world data have been conducted. The experimental results on synthetic data confirm the utility of Magic sets for disjunctive Datalog, and they highlight the computational gain that may be obtained by the new method with respect to the previously proposed Magic set method for disjunctive Datalog programs. Further experiments on data taken from a real-life application show the benefits of the Magic set method within an application scenario that has received considerable att

关键词： Logic programming Stable models Magic sets answer set programming Data integration

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Hybrid ASP-based Approach to Pattern Mining

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THEORY AND PRACTICE OF LOGIC programming 2019年第4期19卷 505-535页

作者： Paramonov, Sergey Stepanova, Daria Miettinen, Pauli Katholieke Univ Leuven Leuven Belgium Max Planck Inst Informat Saarbrucken Germany

Detecting small sets of relevant patterns from a given data set is a central challenge in data mining The relevance of a pattern is based on user-provided criteria;typically, all patterns that satisfy certain criteria are considered relevant. Rule-based languages like answer set programming (ASP) seem well suited for specifying such criteria in a form of constraints. Although progress has been made, on the one hand, on solving individual mining problems and, on the other hand, developing generic mining systems, the existing methods focus either on scalability or on generality. In this paper, we make steps toward combining local (frequency, size, and cost) and global (various condensed representations like maximal, closed, and skyline) constraints in a generic and efficient way. We present a hybrid approach for itemset, sequence, and graph mining which exploits dedicated highly optimized mining systems to detect frequent patterns and then filters the results using declarative ASP. To further demonstrate the generic nature of our hybrid framework, we apply it to a problem of approximately tiling a database. Experiments on real-world data sets show the effectiveness of the proposed method and computational gains for itemset, sequence, and graph mining, as well as approximate tiling. Under consideration in Theory and Practice of Logic programming.

关键词： answer set programming pattern mining structured mining sequence mining itemset mining graph mining

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Forgetting auxiliary atoms in forks

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ARTIFICIAL INTELLIGENCE 2019年 275卷 575-601页

作者： Aguado, Felicidad Cabalar, Pedro Fandinno, Jorge Pearce, David Perez, Gilberto Vidal, Concepcion Univ A Coruna CITIC Res Ctr La Coruna Spain Toulouse Univ Inst Rech Informat Toulouse Toulouse France Univ Potsdam Potsdam Germany Univ Politecn Madrid Madrid Spain

In this work we tackle the problem of checking strong equivalence of logic programs that may contain local auxiliary atoms, to be removed from their stable models and to be forbidden in any external context. We call this property projective strong equivalence (PSE). It has been recently proved that not any logic program containing auxiliary atoms can be reformulated, under PSE, as another logic program or formula without them - this is known as strongly persistent forgetting. In this paper, we introduce a conservative extension of Equilibrium Logic and its monotonic basis, the logic of Here-and-There, in which we deal with a new connective 'vertical bar' we call fork. We provide a semantic characterisation of PSE for forks and use it to show that, in this extension, it is always possible to forget auxiliary atoms under strong persistence. We further define when the obtained fork is representable as a regular formula. (C) 2019 Elsevier B.V. All rights reserved.

关键词： answer set programming Non-monotonic reasoning Equilibrium logic Denotational semantics Forgetting Strong equivalence

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An Application of ASP Theories of Intentions to Understanding Restaurant Scenarios: Insights and Narrative Corpus

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THEORY AND PRACTICE OF LOGIC programming 2020年第2期20卷 273-293页

作者： Zhang, Qinglin Benton, Chris Inclezan, Daniela Miami Univ Coll Engn & Comp Oxford OH 45056 USA

This paper presents a practical application of answer set programming to the understanding of narratives about restaurants. While this task was investigated in depth by Erik Mueller,exceptionalscenarios remained a serious challenge for his script-based story comprehension system. We present a methodology that remedies this issue by modeling characters in a restaurant episode asintentional agents. We focus especially on the refinement of certain components of this methodology in order to increase coverage and performance. We present a restaurant story corpus that we created to design and evaluate our methodology.

关键词： answer set programming natural language understanding intentional agents

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Problem Decomposition and Multi-shot ASP Solving for Job-shop Scheduling

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THEORY AND PRACTICE OF LOGIC programming 2022年第4期22卷 623-639页

作者： El-Kholany, Mohammed M. S. Gebser, Martin Schekotihin, Konstantin Univ Klagenfurt Klagenfurt Austria Cairo Univ Cairo Egypt Graz Univ Technol Graz Austria

Scheduling methods are important for effective production and logistics management, where tasks need to be allocated and performed with limited resources. In particular, the Job-shop Scheduling Problem (JSP) is a well known and challenging combinatorial optimization problem in which tasks sharing a machine are to be arranged in a sequence such that encompassing jobs can be completed as early as possible. Given that already moderately sized JSP instances can be highly combinatorial, and neither optimal schedules nor the runtime to termination of complete optimization methods is known, efficient approaches to approximate good-quality schedules are of interest. In this paper, we propose problem decomposition into time windows whose operations can be successively scheduled and optimized by means of multi-shot answer set programming (ASP) solving. From a computational perspective, decomposition aims to split highly complex scheduling tasks into better manageable subproblems with a balanced number of operations so that good-quality or even optimal partial solutions can be reliably found in a small fraction of runtime. Regarding the feasibility and quality of solutions, problem decomposition must respect the precedence of operations within their jobs and partial schedules optimized by time windows should yield better global solutions than obtainable in similar runtime on the entire instance. We devise and investigate a variety of decomposition strategies in terms of the number and size of time windows as well as heuristics for choosing their operations. Moreover, we incorporate time window overlapping and compression techniques into the iterative scheduling process to counteract window-wise optimization limitations restricted to partial schedules. Our experiments on JSP benchmark sets of several sizes show that successive optimization by multi-shot ASP solving leads to substantially better schedules within the runtime limit than global optimization on the full problem, whe

关键词： job-shop scheduling problem answer set programming problem decomposition

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An ASP-based Solution to the Chemotherapy Treatment Scheduling problem

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THEORY AND PRACTICE OF LOGIC programming 2021年第6期21卷 835-851页

作者： Dodaro, Carmine Galata, Giuseppe Grioni, Andrea Maratea, Marco Mochi, Marco Porro, Ivan Univ Calabria Calabria Italy SurgiQ Srl Genoa Italy San Martino Hosp Genoa Italy Univ Genoa Genoa Italy

The problem of scheduling chemotherapy treatments in oncology clinics is a complex problem, given that the solution has to satisfy (as much as possible) several requirements such as the cyclic nature of chemotherapy treatment plans, maintaining a constant number of patients, and the availability of resources, for example, treatment time, nurses, and drugs. At the same time, realizing a satisfying schedule is of upmost importance for obtaining the best health outcomes. In this paper we first consider a specific instance of the problem which is employed in the San Martino Hospital in Genova, Italy, and present a solution to the problem based on answer set programming (ASP). Then, we enrich the problem and the related ASP encoding considering further features often employed in other hospitals, desirable also in S. Martino, and/or considered in related papers. Results of an experimental analysis, conducted on the real data provided by the San Martino Hospital, show that ASP is an effective solving methodology also for this important scheduling problem.

关键词： healthcare chemotherapy treatment scheduling answer set programming

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An ASP approach for the valves positioning optimization in a water distribution system

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JOURNAL OF LOGIC AND COMPUTATION 2015年第6期25卷 1351-1369页

作者： Gavanelli, Marco Nonato, Maddalena Peano, Andrea Univ Ferrara EnDiF I-44122 Ferrara Italy

Positioning of valves is a real-life issue in Water Distribution System (WDS) design and, currently, it is usually addressed by hydraulic engineers either by hand or by means of genetic algorithms, that give no assurance of optimality. Since a given valves placement identifies a sectorization of the WDS in several isolable portions, the valves positioning problem can be seen as a variant of the well known graph partitioning problem, which is a hard combinatorial problem. Cattafi et al. (2011, TPLP, 11, 731-747) showed recently that Computational Logic can provide technologies and techniques that can be exploited to model and achieve the optimal partition of the water network (i.e. the optimal positioning of valves). In particular, the authors tackled the optimization of the valves positioning through a two player game model, giving a Constraint Logic programming formalization to solve it effectively. The aim of this article, instead, is to investigate the potential of answer set programming in this practical application;evaluation is in terms both of language expressivity and solving efficiency. Results are discussed for different ASP models and a comparison with the CLP(FD) technique shown by Cattafi et al. (2011, TPLP, 11, 731-747) will be given.

关键词： answer set programming isolation system design valves positioning hydroinformatics

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On the Configuration of More and Less Expressive Logic Programs

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THEORY AND PRACTICE OF LOGIC programming 2023年第2期23卷 415-443页

作者： Dodaro, Carmine Maratea, Marco Vallati, Mauro Univ Calabria Arcavacata Di Rende Italy Univ Genoa Genoa Italy Univ Huddersfield Huddersfield HD1 3DH W Yorkshire England

The decoupling between the representation of a certain problem, that is, its knowledge model, and the reasoning side is one of main strong points of model-based artificial intelligence (AI). This allows, for example, to focus on improving the reasoning side by having advantages on the whole solving process. Further, it is also well known that many solvers are very sensitive to even syntactic changes in the input. In this paper, we focus on improving the reasoning side by taking advantages of such sensitivity. We consider two well-known model-based AI methodologies, SAT and ASP, define a number of syntactic features that may characterise their inputs, and use automated configuration tools to reformulate the input formula or program. Results of a wide experimental analysis involving SAT and ASP domains, taken from respective competitions, show the different advantages that can be obtained by using input reformulation and configuration.

关键词： SATisfiability answer set programming knowledge configuration

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About Epistemic Negation and World Views in Epistemic Logic Programs

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THEORY AND PRACTICE OF LOGIC programming 2019年第5-6期19卷 790-807页

作者： Costantini, Stefania Univ Aquila DISIM Laquila Italy

In this paper we consider Epistemic Logic Programs, which extend answer set programming (ASP) with "epistemic operators" and "epistemic negation", and a recent approach to the semantics of such programs in terms of World Views. We propose some observations on the existence and number of world views. We show how to exploit an extended ASP semantics in order to: (i) provide a characterization of world views, different from existing ones;(ii) query world views and query the whole set of world views.

关键词： answer set programming Epistemic Logic Programs Epistemic Negation

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