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Domain-Independent Cost-Optimal Planning in ASP

THEORY AND PRACTICE OF LOGIC programming 2019年第5-6期19卷 1124-1141页

作者： Spies, David You, Jia-Huai Hayward, Ryan Univ Alberta Edmonton AB Canada

We investigate the problem of cost-optimal planning in ASP. Current ASP planners can be trivially extended to a cost-optimal one by adding weak constraints, but only for a given makespan (number of steps). It is desirable to have a planner that guarantees global optimality. In this paper, we present two approaches to addressing this problem. First, we show how to engineer a cost-optimal planner composed of two ASP programs running in parallel. Using lessons learned from this, we then develop an entirely new approach to cost-optimal planning, stepless planning, which is completely free of makespan. Experiments to compare the two approaches with the only known cost-optimal planner in SAT reveal good potentials for stepless planning in ASP.

关键词： Cost-Optimal Planning answer set programming CORE-2 ASP Standard

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Founded (Auto) Epistemic Equilibrium Logic Satisfies Epistemic Splitting

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THEORY AND PRACTICE OF LOGIC programming 2019年第5-6期19卷 671-687页

作者： Fandinno, Jorge Univ Toulouse IRIT CNRS Toulouse France

In a recent line of research, two familiar concepts from logic programming semantics (unfounded sets and splitting) were extrapolated to the case of epistemic logic programs. The property of epistemic splitting provides a natural and modular way to understand programs without epistemic cycles but, surprisingly, was only fulfilled by Gelfond's original semantics (G91), among the many proposals in the literature. On the other hand, G91 may suffer from a kind of self-supported, unfounded derivations when epistemic cycles come into play. Recently, the absence of these derivations was also formalised as a property of epistemic semantics called foundedness. Moreover, a first semantics proved to satisfy foundedness was also proposed, the so-called Founded Autoepistemic Equilibrium Logic (FAEEL). In this paper, we prove that FAEEL also satisfies the epistemic splitting property something that, together with foundedness, was not fulfilled by any other approach up to date. To prove this result, we provide an alternative characterisation of FAEEL as a combination of G91 with a simpler logic we called Founded Epistemic Equilibrium Logic (FEEL), which is somehow an extrapolation of the stable model semantics to the modal logic S5.

关键词： answer set programming Epistemic Specifications Epistemic Logic Programs

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Reasoning on DL-LiteR with Defeasibility in ASP

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THEORY AND PRACTICE OF LOGIC programming 2022年第2期22卷 254-304页

作者： Bozzato, Loris Eiter, Thomas Serafini, Luciano Fdn Bruno Kessler Via Sommar 18 I-38123 Trento Italy Tech Univ Wien Favoritenstr 9-11 A-1040 Vienna Austria

Reasoning on defeasible knowledge is a topic of interest in the area of description logics, as it is related to the need of representing exceptional instances in knowledge bases. In this direction, in our previous works we presented a framework for representing (contextualized) OWL RL knowledge bases with a notion of justified exceptions on defeasible axioms: reasoning in such framework is realized by a translation into ASP programs. The resulting reasoning process for OWL RL, however, introduces a complex encoding in order to capture reasoning on the negative information needed for reasoning on exceptions. In this paper, we apply the justified exception approach to knowledge bases in DL-Lite(R), that is, the language underlying OWL QL. We provide a definition for DL-Lite(R )knowledge bases with defeasible axioms and study their semantic and computational properties. In particular, we study the effects of exceptions over unnamed individuals. The limited form of DL-Lite(R) axioms allows us to formulate a simpler ASP encoding, where reasoning on negative information is managed by direct rules. The resulting materialization method gives rise to a complete reasoning procedure for instance checking in DL-LiteR with defeasible axioms.(1)

关键词： defeasible knowledge description logics answer set programming justifiable exceptions

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Maintenance goals of agents in a dynamic environment:: Formulation and policy construction

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ARTIFICIAL INTELLIGENCE 2008年第12-13期172卷 1429-1469页

作者： Baral, Chitta Eiter, Thomas Bjareland, Marcus Nakamura, Mutsumi Arizona State Univ Dept Comp Sci & Engn Tempe AZ 85287 USA AstraZeneca R&D S-43183 Molndal Sweden Vienna Univ Technol Inst Informat Syst A-1040 Vienna Austria

The notion of maintenance often appears in the AI literature in the context of agent behavior and planning. In this paper, we argue that earlier characterizations of the notion of maintenance are not intuitive to characterize the maintenance behavior of certain agents in a dynamic environment. We propose a different characterization of maintenance and distinguish it from earlier notions such as stabilizability. Our notion of maintenance is more sensitive to a good-natured agent which struggles with an "adversary" environment, which hinders her by unforeseeable events to reach her goals (not in principle, but in case). It has a parameter k, referring to the length of non-interference (from exogenous events) needed to maintain a goal;we refer to this notion as k-maintainability. We demonstrate the notion on examples, and address the important but non-trivial issue of efficient construction of maintainability control functions. We present an algorithm which in polynomial time constructs a k-maintainable control function, if one exists, or tells that no such control is possible. Our algorithm is based on SAT Solving, and employs a suitable formulation of the existence of k-maintainable control in a fragment of SAT which is tractable. For small k (bounded by a constant), our algorithm is linear time. We then give a logic programming implementation of our algorithm and use it to give a standard procedural algorithm, and analyze the complexity of constructing k-maintainable controls, under different assumptions such as k = 1, and states described by variables. On the one hand, our work provides new concepts and algorithms for maintenance in dynamic environment, and on the other hand, a very fruitful application of computational logic tools. We compare our work with earlier works on control synthesis from temporal logic specification and relate our work to Dijkstra's notion of self-stabilization and related notions in distributed computing. (c) 2008 Elsevier B.V. All rights

关键词： maintenance goals k-maintainability agent control computational complexity of agent design answer set programming horn theories SAT solving discrete event dynamic systems self-stabilization

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Mining External Sources in answer set Programs

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THEORY AND PRACTICE OF LOGIC programming 2019年第3期19卷 360-411页

作者： Redl, Christoph Vienna Univ Technol Inst Log & Computat Favoritenstr 9-11 A-1040 Vienna Austria

HEX-programs are an extension of answer set programs (ASP) with external sources. To this end, external atoms provide a bidirectional interface between the program and an external source. The traditional evaluation algorithm for HEX-programs is based on guessing truth values of external atoms and verifying them by explicit calls of the external source. The approach was optimized by techniques that reduce the number of necessary verification calls or speed them up, but the remaining external calls are still expensive. In this paper, we present an alternative evaluation approach based on Wining of external atoms, motivated by existing but less general approaches for specialized formalisms such as DL-programs. External atoms are then compiled away such that no verification calls are necessary. The approach is implemented in the dlvhex reasoner. Experiments show a significant performance gain. Besides performance improvements, we further exploit inlining rig for extending previous (semantic) characterizations of program equivalence from ASP to HEX-programs, including those of strong equivalence, uniform equivalence, and (H, B)equivalence. Finally, based on these equivalence criteria, we characterize also inconsistency of programs w.r.t. extensions. Since well-known ASP extensions (such as constraint ASP) are special cases of HEX, the results are interesting beyond the particular formalism.

关键词： answer set programming external computation HEX-programs inlining equivalence

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Conflict-driven answer set solving: From theory to practice

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ARTIFICIAL INTELLIGENCE 2012年 187卷 52-89页

作者： Gebser, Martin Kaufmann, Benjamin Schaub, Torsten Univ Potsdam Inst Informat D-14482 Potsdam Germany Simon Fraser Univ Sch Comp Sci Burnaby BC V5A 1S6 Canada Griffith Univ Inst Integrated & Intelligent Syst Brisbane Qld 4111 Australia

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. (C) 2012 Elsevier B.V. All rights reserved.

关键词： answer set programming Logic programming Nonmonotonic reasoning

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LOG-IDEAH: LOGic trees for identification of damage due to earthquakes for architectural heritage

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BULLETIN OF EARTHQUAKE ENGINEERING 2015年第1期13卷 153-176页

作者： Novelli, V. I. D'Ayala, D. UCL London WC1E 6BT England

In the framework of PERPETUATE, LOG-IDEAH: "LOGic trees for Identification of Damage due to Earthquakes for Architectural Heritage" has been developed as a post-earthquake assessment tool for the evaluation of the global seismic performance of architectural assets (AAs). LOG-IDEAH is an expert system which interprets the seismic damage collected on site by relying on the knowledge of engineers and architects in seismic vulnerability assessment. The present expert system has been set up on logic trees, implemented in answer set programming to encode the recognition process that surveyors proceed to investigate the causes of damage and to evaluate the failures occurring on an AA. LOG-IDEAH, available at (http://***/), allows sketching AAs, recording the state of damage, uploading GPS referenced images and comparing collapse mechanisms observed on site with collapse mechanisms identified by the system. The seismic damage, which is the minimum data required by LOG-IDEAH, is collected at the level of both structural elements and artistic assets (local level) and interpreted at the level of the AA (global level). The answer set programming applied for the construction of the machine-processable representation, once the input data has been recorded into the web-interface, provides all possible failure modes and related possibilities of occurrence by taking into consideration the reliability level of the collected data. Its capability has been validated by applying LOG-IDEAH to the historic centre of L'Aquila of the 2009 earthquake by pointing out that answer set programming is a valid alternative approach to the existing methods developed to identify the seismic performance of masonry AAs.

关键词： Semantic expert system answer set programming Masonry historic architectural assets Damage scenarios Post-earthquake assessment Global mechanisms

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Finitely recursive programs: Decidability and bottom-up computation

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AI COMMUNICATIONS 2011年第4期24卷 311-334页

作者： Calimeri, Francesco Cozza, Susanna Ianni, Giovambattista Leone, Nicola Univ Calabria Dipartimento Matemat I-87036 Arcavacata Di Rende Italy Univ Calabria Dipartimento Elettron Informat & Sistemist I-87036 Arcavacata Di Rende Italy

The support for function symbols in logic programming under answer set semantics allows us to overcome some modeling limitations of traditional answer set programming (ASP) systems, such as the inability of handling infinite domains. On the other hand, admitting function symbols in ASP makes inference undecidable in the general case. Recently, the research community has been focusing on finding proper subclasses of programs with functions for which decidability of inference is guaranteed. The two major proposals, so far, are finitary programs and finitely-ground programs. These two proposals are somehow complementary: indeed, the former is conceived to allow decidable querying (by means of a top-down evaluation strategy), while the latter supports the computability of answer sets (by means of a bottom-up evaluation strategy). One of the main advantages of finitely-ground programs is that they can be "directly" evaluated by current ASP systems, which are based on a bottom-up computational model. However, there are also some interesting programs which are suitable for top-down query evaluation;but they do not fall in the class of finitely-ground programs. In this paper, we focus on disjunctive finitely recursive positive (DFRP) programs. We design a version of the magic sets technique for DFRP programs, which ensures query equivalence under both brave and cautious reasoning. We show that, if the input program is DFRP, then its magic-sets rewriting is guaranteed to be finitely ground. Reasoning on DFRP programs turns out to be decidable;and we provide also an effective method that allows one to simply perform this reasoning by using the ASP system DLV.

关键词： answer set programming function symbols magic sets knowledge representation

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Diagnostic reasoning with A-Prolog

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THEORY AND PRACTICE OF LOGIC programming 2003年第4-5期3卷 425-461页

作者： Balduccini, M Gelfond, M Texas Tech Univ Dept Comp Sci Lubbock TX 79409 USA

In this paper, we suggest an architecture for a software agent which operates a physical device and is capable of making observations and of testing and repairing the device's components. We present simplified definitions of the notions of symptom, candidate diagnosis, and diagnosis which are based on the theory of action language A L. The definitions allow one to give a simple account of the agent's behavior in which many of the agent's tasks are reduced to computing stable models of logic programs.

关键词： answer set programming diagnostic reasoning intelligent agents

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Restricting data-leakage using fine-grained access control on OSN objects

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INTERNATIONAL JOURNAL OF INFORMATION SECURITY 2023年第1期22卷 93-106页

作者： Rathore, Nemi Chandra Tripathy, Somanath Cent Univ South Bihar Dept Comp Sci Gaya Bihar India Indian Inst Technol Patna Dept Comp Sci & Engn Bihta Bihar India

In recent years, Online Social Networks like Facebook, Twitter have become an integral part of our daily life to share a variety of information with others. These information contents are accessible to a large group of Internet users causing a serious privacy risk. In this paper, we propose a simple and flexible access control model to regulate access to users' resources on Twitter. Our proposed model employs an object matrix and access capability list to enable users to regulate access to their private resources and can be tuned to other Online Social Networks. The main advantages of our model are its simplicity and ease of deployment. The correctness of the access control model is verified using a logical model in answer set programming. The efficiency and feasibility of our mechanism is evaluated through a prototype.

关键词： Online social networks (OSNs) Privacy Access control Third-party applications Accessor capability list (ACPL) answer set programming

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