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30th international conference on logic programming

作者： Bartak, Roman Zhou, Neng-Fa Charles Univ Prague Fac Math & Phys Prague Czech Republic CUNY Brooklyn Coll New York NY USA

Tabling has been used for some time to improve efficiency of Prolog programs by memorizing answered queries. the same idea can be naturally used to memorize visited states during search for planning. In this paper we present a planner developed in the Picat language to solve the Petrobras planning problem. Picat is a novel Prolog-like language that provides pattern matching, deterministic and non-deterministic rules, and tabling as its core modelling and solving features. We demonstrate these capabilities using the Petrobras problem, where the goal is to plan transport of cargo items from ports to platforms using vessels with limited capacity. Monte Carlo Tree Search has been so far the best technique to tackle this problem and we will show that by using tabling we can achieve much better runtime efficiency and better plan quality.

关键词： tabling resource-bounded search symmetry breaking planning logistics

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On Cascade Products of Answer Set Programs

On Cascade Products of Answer Set Programs

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30th international conference on logic programming

作者： Antic, Christian Vienna Univ Technol Inst Informat Syst A-1040 Vienna Austria

Describing complex objects by elementary ones is a common strategy in mathematics and science in general. In their seminal 1965 paper, Kenneth Krohn and John Rhodes showed that every finite deterministic automaton can be represented (or "emulated") by a cascade product of very simple automata. this led to an elegant algebraic theory of automata based on finite semigroups (Krohn-Rhodes theory). Surprisingly, by relating logic programs and automata, we can show in this paper that the Krohn-Rhodes theory is applicable in Answer Set programming (ASP). More precisely, we recast the concept of a cascade product to ASP, and prove that every program can be represented by a product of very simple programs, the reset and standard programs. Roughly, this implies that the reset and standard programs are the basic building blocks of ASP with respect to the cascade product. In a broader sense, this paper is a first step towards an algebraic theory of products and networks of nonmonotonic reasoning systems based on Krohn-Rhodes theory, aiming at important open issues in ASP and AI in general.

关键词： Answer Set programming (ASP) Krohn-Rhodes theory Automata

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Resource Usage Analysis of logic Programs via Abstract Interpretation Using Sized Types

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thEORY AND PRACTICE OF logic programming 2014年第4-5期14卷 739-754页

作者： Serrano, A. Lopez-Garcia, P. Hermenegildo, M. V. Univ Utrecht Dept Informat & Comp Sci NL-3508 TC Utrecht Netherlands IMDEA Software Inst Madrid Spain CSIC Spanish Council Sci Res Madrid Spain Tech Univ Madrid UPM Madrid Spain

We present a novel general resource analysis for logic programs based on sized types. Sized types are representations that incorporate structural (shape) information and allow expressing both lower and upper bounds on the size of a set of terms and their subterms at any position and depth. they also allow relating the sizes of terms and subterms occurring at different argument positions in logic predicates. Using these sized types, the resource analysis can infer both lower and upper bounds on the resources used by all the procedures in a program as functions on input term (and subterm) sizes, overcoming limitations of existing resource analyses and enhancing their precision. Our new resource analysis has been developed within the abstract interpretation framework, as an extension of the sized types abstract domain, and has been integrated into the Ciao preprocessor, CiaoPP. the abstract domain operations are integrated with the setting up and solving of recurrence equations for inferring both size and resource usage functions. We show that the analysis is an improvement over the previous resource analysis present in CiaoPP and compares well in power to state of the art systems.

关键词： analysis programme Upper bound Formal logic logic programming

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the P-Box CDF-Intervals: A Reliable Constraint Reasoning with Quantifiable Information

The P-Box CDF-Intervals: A Reliable Constraint Reasoning wit...

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30th international conference on logic programming

作者： Saad, Aya Fruehwirth, thom Gervet, Carmen Univ Ulm D-89069 Ulm Germany Univ Savoie Savoie France

this paper introduces a new constraint domain for reasoning about data with uncertainty. It extends convex modeling with the notion of p-box to gain additional quantifiable information on the data whereabouts. Unlike existing approaches, the p-box envelops an unknown probability instead of approximating its representation. the p-box bounds are uniform cumulative distribution functions (cdf)in order to employ linear computations in the probabilistic domain. the reasoning by means of p-box cdf-intervals is an interval computation which is exerted on the real domain then it is projected onto the cdf domain. this operation conveys additional knowledge represented by the obtained probabilistic bounds. the empirical evaluation of our implementation shows that, with minimal overhead, the output solution set realizes a full enclosure of the data along with tighter bounds on its probabilistic distributions.

关键词： convex structures reliable constraint reasoning probability box cdf interval constraint satisfaction problem constraint programming constraint reasoning uncertainty

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A Proof theoretic Study of Soft Concurrent Constraint programming

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thEORY AND PRACTICE OF logic programming 2014年第4-5期14卷 649-663页

作者： Pimentel, Elaine Olarte, Carlos Nigam, Vivek Univ Fed Rio Grande do Norte BR-59072970 Natal RN Brazil Pontificia Univ Javeriana Cali Javeriana Colombia Univ Fed Paraiba BR-58059900 Joao Pessoa Paraiba Brazil

Concurrent Constraint programming (CCP) is a simple and powerful model for concurrency where agents interact by telling and asking constraints. Since their inception, CCP-languages have been designed for having a strong connection to logic. In fact, the underlying constraint system can be built from a suitable fragment of intuitionistic (linear) logic -ILL- and processes can be interpreted as formulas in ILL. Constraints as ILL formulas fail to represent accurately situations where "preferences" (called soft constraints) such as probabilities, uncertainty or fuzziness are present. In order to circumvent this problem, c-semirings have been proposed as algebraic structures for defining constraint systems where agents are allowed to tell and ask soft constraints. Nevertheless, in this case, the tight connection to logic and proof theory is lost. In this work, we give a proof theoretical meaning to soft constraints: they can be defined as formulas in a suitable fragment of ILL with subexponentials (SELL) where subexponentials, ordered in a c-semiring structure, are interpreted as preferences. We hence achieve two goals: (1) obtain a CCP language where agents can tell and ask soft constraints and (2) prove that the language in (1) has a strong connection with logic. Hence we keep a declarative reading of processes as formulas while providing a logical framework for soft-CCP based systems. An interesting side effect of (1) is that one is also able to handle probabilities (and other modalities) in SELL, by restricting the use of the promotion rule for non-idempotent c-semirings. this finer way of controlling subexponentials allows for considering more interesting spaces and restrictions, and it opens the possibility of specifying more challenging computational systems.

关键词： Concurrent Constraint programming Linear logic Soft Constraints

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Causal Graph Justifications of logic Programs

Causal Graph Justifications of Logic Programs

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30th international conference on logic programming

作者： Cabalar, Pedro Fandinno, Jorge Fink, Michael Univ A Coruna Dept Comp Sci Coruna Spain Vienna Univ Technol Inst Informat Syst A-1040 Vienna Austria

In this work we propose a multi-valued extension of logic programs under the stable models semantics where each true atom in a model is associated with a set of justifications. these justifications are expressed in terms of causal graphs formed by rule labels and edges that represent their application ordering. For positive programs, we show that the causal justifications obtained for a given atom have a direct correspondence to (relevant) syntactic proofs of that atom using the program rules involved in the graphs. the most interesting contribution is that this causal information is obtained in a purely semantic way, by algebraic operations (product, sum and application) on a lattice of causal values whose ordering relation expresses when a justification is stronger than another. Finally, for programs with negation, we define the concept of causal stable model by introducing an analogous transformation to Gelfond and Lifschitz's program reduct. As a result, default negation behaves as "absence of proof" and no justification is derived from negative literals, something that turns out convenient for elaboration tolerance, as we explain with a running example.

关键词： Answer Set programming Causality Knowledge Representation Multi-valued logic programming

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A Module System for Domain-Specific Languages

A Module System for Domain-Specific Languages

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30th international conference on logic programming

作者： Jackson, Ethan K. Microsoft Res Res Software Engn RiSE Redmond WA 98052 USA

Domain-specific languages (DSLs) are routinely created to simplify difficult or specialized programming tasks. they expose useful abstractions and design patterns in the form of language constructs, provide static semantics to eagerly detect misuse of these constructs, and dynamic semantics to completely define how language constructs interact. However, implementing and composing DSLs is a non-trivial task, and there is a lack of tools and techniques. We address this problem by presenting a complete module system over LP for DSL construction, reuse, and composition. LP is already useful for DSL design, because it supports executable language specifications using notations familiar to language designers. We extend LP with a module system that is simple (with a few concepts), succinct (for key DSL specification scenarios), and composable (on the level of languages, compilers, and programs). these design choices reflect our use of LP for industrial DSL design. Our module system has been implemented in the formula language, and was used to build key Windows 8 device drivers via DSLs. though we present our module system as it actually appears in our formula language, our emphasis is on concepts adaptable to other LP languages.

关键词： module systems domain-specific languages logic programming

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claspfolio 2: Advances in Algorithm Selection for Answer Set programming

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thEORY AND PRACTICE OF logic programming 2014年第4-5期14卷 569-585页

作者： Hoos, Holger Lindauer, Marius Schaub, Torsten Univ British Columbia Vancouver BC V5Z 1M9 Canada Univ Freiburg Freiburg Germany Univ Potsdam Potsdam Germany

Building on the award-winning, portfolio-based ASP solver claspfolio, we present claspfolio 2, a modular and open solver architecture that integrates several different portfolio-based algorithm selection approaches and techniques. the claspfolio 2 solver framework supports various feature generators, solver selection approaches, solver portfolios, as well as solver-schedule-based pre-solving techniques. the default configuration of claspfolio 2 relies on a light-weight version of the ASP solver clasp to generate static and dynamic instance features. the flexible open design of claspfolio 2 is a distinguishing factor even beyond ASP. As such, it provides a unique framework for comparing and combining existing portfolio-based algorithm selection approaches and techniques in a single, unified framework. Taking advantage of this, we conducted an extensive experimental study to assess the impact of different feature sets, selection approaches and base solver portfolios. In addition to gaining substantial insights into the utility of the various approaches and techniques, we identified a default configuration of claspfolio 2 that achieves substantial performance gains not only over clasp's default configuration and the earlier version of claspfolio, but also over manually tuned configurations of clasp.

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Automated Operator Placement in Distributed Data Stream Management Systems Subject to User Constraints

Automated Operator Placement in Distributed Data Stream Mana...

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IEEE 30th international conference on Data Engineering (ICDE)

作者： thoma, Cory Labrinidis, Alexandros Lee, Adam J. Univ Pittsburgh Dept Comp Sci Pittsburgh PA 15260 USA

ISBN: (纸本)9781479934812

Traditional distributed Data Stream Management Systems assign query operators to sites by optimizing for some criterion such as query throughput, or network delay. the work presented in this paper begins to augment this traditional operator placement technique by allowing the user issuing a continuous query to specify a variety of constraints-including collocation, upstream/downstream, and tag- or attribute-based constraints-controlling operator placement within the query network. Given a set of constraints, operators, and sites;four strategies are presented for optimizing the operator placement. An optimal brute force algorithm is presented first for smaller cases, followed by linear programming, constraint satisfaction, and local search strategies. the four methods are compared for speed, accuracy, and efficiency, with constraint satisfaction performing the best, and allowing assignments to be adapted on the fly by the DDSMS.

关键词： Linear programming

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Contextual Abductive Reasoning with Side-Effects

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thEORY AND PRACTICE OF logic programming 2014年第4-5期14卷 633-648页

作者： Pereira, Luis Moniz Dietz, Emmanuelle-Anna Hoelldobler, Steffen Univ Nova Lisboa Fac Ciencias & Tecnol Dept Informat Ctr Inteligencia Artificial CENTRIA P-2829516 Caparica Portugal Tech Univ Dresden Int Ctr Computat Logi D-01062 Dresden Germany

the belief bias effect is a phenomenon which occurs when we think that we judge an argument based on our reasoning, but are actually influenced by our beliefs and prior knowledge. Evans, Barston and Pollard carried out a psychological syllogistic reasoning task to prove this effect. Participants were asked whether they would accept or reject a given syllogism. We discuss one specific case which is commonly assumed to be believable but which is actually not logically valid. By introducing abnormalities, abduction and background knowledge, we adequately model this case under the weak completion semantics. Our formalization reveals new questions about possible extensions in abductive reasoning. For instance, observations and their explanations might include some relevant prior abductive contextual information concerning some side-effect or leading to a contestable or refutable side-effect. A weaker notion indicates the support of some relevant consequences by a prior abductive context. Yet another definition describes jointly supported relevant consequences, which captures the idea of two observations containing mutually supportive side-effects. though motivated with and exemplified by the running psychology application, the various new general abductive context definitions are introduced here and given a declarative semantics for the first time, and have a much wider scope of application. Inspection points, a concept introduced by Pereira and Pinto, allows us to express these definitions syntactically and intertwine them into an operational semantics.

关键词： Abductive Reasoning Contextual Reasoning Side-effects Human Reasoning Belief-Bias Inspection Points three-valued Lukasiewicz logic Weak Completion Semantics logic programming

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