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PPDP 2008: 10th international ACM SIGPLAN symposium on Principles and Practice of Declarative programming

作者： Pientka, Brigitte Dunfield, Jana School of Computer Science McGill University Montreal QC Canada

ISBN: (纸本)9781605581170

this paper explores a new point in the design space of functional programming: functional programming with dependently-typed higher-order data structures described in the logical framework LF. this allows us to program with proofs as higher-order data. We present a decidable bidirectional type system that distinguishes between dependently-typed data and computations. To support reasoning about open data, our foundation makes contexts explicit. this provides us with a concise characterization of open data, which is crucial to elegantly describe proofs. In addition, we present an operational semantics for this language based on higher-order pattern matching for dependently typed objects. Based on this development, we prove progress and preservation. Copyright © 2008 ACM.

关键词： functional programming

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PPDP 2008: 10th international ACM SIGPLAN symposium on Principles and Practice of Declarative programming

作者： Caballero, Rafael Rodríguez-Artalejo, Mario Romero-Díaz, Carlos A. Departamento de Sistemas Informáticos y Computación Universidad Complutense de Madrid Spain

ISBN: (纸本)9781605581170

Similarity-based logic programming (briefly, SLP) has been proposed to enhance the LP paradigm with a kind of approximate reasoning which supports flexible information retrieval applications. this approach uses a fuzzy similarity relation R between symbols in the program's signature, while keeping the syntax for program clauses as in classical LP. Another recent proposal is the QLP(P) scheme for Qualified logic programming, an extension of the LP paradigm which supports approximate reasoning and more. this approach uses annotated program clauses and a para-metrically given domain D whose elements qualify logical assertions by measuring their closeness to various users' expectations. In this paper we propose a more expressive scheme SQLP(R, D) which subsumes both SLP and QLP(D) as particular cases. We also show that SQLP(R, D) programs can be transformed into se-mantically equivalent SQLP(R, D) programs. As a consequence, existing QLP(D) implementations can be used to give efficient support for similarity-based reasoning. Copyright © 2008 ACM.

关键词： logic programming

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Exploiting conjunctive queries in description logic programs

Exploiting conjunctive queries in description logic programs

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10th international symposium on Artificial Intelligence and Mathematics

作者： Eiter, thomas Ianni, Giovambattista Krennwallner, thomas Schindlauer, Roman Vienna Univ Technol Inst Informat Syst 184 3 A-1040 Vienna Austria Univ Calabria Dipartimento Matemat I-87036 Arcavacata Di Rende CS Italy

Towards combining rules and ontologies for the Semantic Web, nonmonotonic Description logic Programs (dl-programs) have been proposed as a powerful formalism to couple nonmonotonic logic programming and Description logic reasoning on a clear semantic basis. In this paper, we present cq-programs, which enhance dl-programs with conjunctive queries (CQ) and union of conjunctive queries (UCQ) over Description logics knowledge bases, as well as with disjunctive rules. the novel formalism has two advantages. First, it offers increased expressivity because it allows for (U)CQs in the bodies of the rules. the (U)CQs allow one to access unnamed individuals in the rules and they increase the expressivity of the formalism, as evident from the increase in complexity from NEXP to 2-EXP. And second, when implemented as a combination between a logic programming system and a DL-reasoner, this integration of rules and ontologies gives rise to strategies for optimizing calls to the DL-reasoner, by exploiting specific support for (U)CQs. To this end, we present equivalence preserving transformations which can be used for program rewriting, and we present respective generic rewriting algorithms. Experimental results for a cq-program prototype show that this can lead to significant performance improvements, and suggest that cq-programs and program rewriting provide a useful basis for dl- and cq-program optimization.

关键词： Hybrid rule languages Conjunctive queries and description logics Answer set programming Semantic web

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Unification of arrays in spreadsheets with logic programming

Unification of arrays in spreadsheets with logic programming

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10th international symposium on Practical Aspects of Declarative Languages

作者： Cox, Philip T. Nicholson, Patrick Dalhousie Univ Fac Comp Sci Halifax NS B3H 1W5 Canada

ISBN: (纸本)9783540774419

Unification, one of the key processes underlying logic programming (LP), provides a powerful mechanism for assembling and disassembling structures, lists in particular, by matching patterns. In recent work, we showed how spreadsheets can be enhanced by adding a visual form of LP in which lists, the fundamental structures of LP, are replaced by rectangular arrays, the fundamental structures of spreadsheets. the benefits include enhanced programmability and a way to specify high level templates for spreadsheet structures. Here, we focus on the structure of arrays, and describe the array unification algorithm underlying our current implementation.

关键词： spreadsheet logic programming array unification

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Dynamic variable elimination during propagation solving 08

Dynamic variable elimination during propagation solving

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PPDP 2008: 10th international ACM SIGPLAN symposium on Principles and Practice of Declarative programming

作者： Schulte, Christian Stuckey, Peter J. ICT KTH Royal Institute of Technology Stockholm Sweden National ICT Australia Victoria Laboratory University of Melbourne Australia

ISBN: (纸本)9781605581170

Constraint propagation solvers interleave propagation (removing impossible values from variables domains) with search. Propagation is performed by executing propagators (removing values) implementing constraints (defining impossible values). In order to specify constraint problems with a propagation solver often many new intermediate variables need to be introduced. Each variable plays a role in calculating the value of some expression. But as search proceeds not all of these expressions will be of interest any longer, but the propagators implementing them will remain active. In this paper we show how we can analyse the propagation graph of the solver in linear time to determine intermediate variables that can be removed without effecting the result. Experiments show that applying this analysis can reduce the space and time requirements for constraint propagation on example problems. Copyright © 2008 ACM.

关键词： logic programming

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Termination of narrowing in left-linear constructor systems 1

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9th international symposium on functional and logic programming

作者： Vidal, German Univ Politecn Valencia Valencia Spain

ISBN: (数字)9783540789697

ISBN: (纸本)9783540789680

Narrowing extends rewriting with logic capabilities by allowing logic variables in terms and replacing matching with unification. Narrowing has been widely used in different contexts, ranging from theorem proving to language design. Surprisingly, the termination of narrowing has been mostly overlooked. In this paper, we present a new approach for analyzing the termination of narrowing in left-linear constructor systems-a widely accepted class of systems-that allows us to reuse existing methods in the literature on termination of rewriting.

关键词： Formal logic

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Exploiting conjunctive queries in description logic programs

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ANNALS OF MAthEMATICS AND ARTIFICIAL INTELLIGENCE 2008年第1-4期53卷 115-152页

关键词： Hybrid rule languages Conjunctive queries and description logics Answer set programming Semantic web

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Pattern by example: Type-driven visual programming of XML queries 08

Pattern by example: Type-driven visual Programming of XML qu...

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PPDP 2008: 10th international ACM SIGPLAN symposium on Principles and Practice of Declarative programming

作者： Benzaken, Véronique Castagna, Giuseppe Colazzo, Dario Miachon, Cédric Université Paris-Sud 11 LR1 Orsay France CNRS PPS Universite Paris 7 Paris France Courtanet Paris France

ISBN: (纸本)9781605581170

We present Pattern-by-Example (PBE), a graphical language that allows users with little or no knowledge of pattern-matching and functional programming to define complex and optimized queries on XML documents. We demonstrate the key features of PBE by commenting an interactive session and then we present its semantics by formally defining a translation from PBE graphical queries into CQL ones. the advantages of the approach are twofold. First, it generates queries that are provably correct with respect to types: the type of the result is displayed to the user and this constitutes a first and immediate visual check of the semantic correctness of the resulting query. the second advantage is that a semantics formally-thus, unambiguously-defined is an important advancement over some current approaches in which standard usage and learning methods are based on "trial and error" techniques. Copyright © 2008 ACM.

关键词： Semantics

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Towards execution time estimation in abstract machine-based languages 08

Towards execution time estimation in abstract machine-based ...

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PPDP 2008: 10th international ACM SIGPLAN symposium on Principles and Practice of Declarative programming

作者： Mera, E. Lopez, P. Carro, M. Hermenegildo, M. Complutense University of Madrid IMDEA Software Technical U. of Madrid U. of New Mexico

ISBN: (纸本)9781605581170

Abstract machines provide a certain separation between platform-dependent and platform-independent concerns in compilation. Many of the differences between architectures are encapsulated in the specific abstract machine implementation and the bytecode is left largely architecture independent. Taking advantage of this fact, we present a framework for estimating upper and lower bounds on the execution times of logic programs running on a bytecode-based abstract machine. Our approach includes a one-time, program-independent profiling stage which calculates constants or functions bounding the execution time of each abstract machine instruction. then, a compile-time cost estimation phase, using the instruction timing information, infers expressions giving platform-dependent upper and lower bounds on actual execution time as functions of input data sizes for each program. Working at the abstract machine level makes it possible to take into account low-level issues in new architectures and platforms by just reexecuting the calibration stage instead of having to tailor the analysis for each architecture and platform. Applications of such predicted execution times include debugging/verification of time properties, certification of time properties in mobile code, granularity control in parallel/distributed computing, and resource-oriented specialization. Copyright © 2008 ACM.

关键词： logic programming

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Global difference constraint propagation for finite domain solvers 08

Global difference constraint propagation for finite domain s...

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PPDP 2008: 10th international ACM SIGPLAN symposium on Principles and Practice of Declarative programming

作者： Feydy, thibaut Schutt, Andreas Stuckey, Peter J. National ICT Australia Victoria Laboratory University of Melbourne Australia

ISBN: (纸本)9781605581170

Difference constraints of the form x - y ≤ d are well studied, with efficient algorithms for satisfaction and implication, because of their connection to shortest paths. Finite domain propagation algorithms however do not make use of these algorithms, and typically treat each difference constraint as a separate propagator. Propagation does guarantee completeness of solving but can be needlessly slow. In this paper we describe how to build a (bounds consistent) global propagator for difference constraints that treats them all simultaneously. SAT modulo theory solvers have included theory solvers for difference constraints for some time. While a theory solver for difference constraints gives the basis of a global difference constraint propagator, we show how the requirements on the propagator are quite different. We give experiments showing that treating difference constraints globally can substantially improve on the standard propagation approach. Copyright © 2008 ACM.

关键词： difference logic propagation global constraints

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