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The Complexity of Global Constraints
, 2004
"... We study the computational complexity of reasoning with global constraints. We show that reasoning with such constraints is intractable in general. We then demonstrate how the same tools of computational complexity can be used in the design and analysis of specific global constraints. In particular ..."
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Cited by 64 (23 self)
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We study the computational complexity of reasoning with global constraints. We show that reasoning with such constraints is intractable in general. We then demonstrate how the same tools of computational complexity can be used in the design and analysis of specific global constraints. In particular, we illustrate how computational complexity can be used to determine when a lesser level of local consistency should be enforced, when decomposing constraints will lose pruning, and when combining constraints is tractable. We also show how the same tools can be used to study symmetry breaking, metaconstraints like the cardinality constraint, and learning nogoods.
Automated Strategies for Specializing Constraint Logic Programs
 LOPSTR 2000, LNCS 2042
"... We consider the problem of specializing constraint logic programs w.r.t. constrained queries. We follow a transformational approach based on rules and strategies. The use of the rules ensures that the specialized program is equivalent to the initial program w.r.t. a given constrained query. The stra ..."
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Cited by 9 (7 self)
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We consider the problem of specializing constraint logic programs w.r.t. constrained queries. We follow a transformational approach based on rules and strategies. The use of the rules ensures that the specialized program is equivalent to the initial program w.r.t. a given constrained query. The strategies guide the application of the rules so to derive an efficient specialized program. In this paper we address various issues concerning the development of an automated transformation strategy. In particular, we consider the problems of when and how we should unfold, replace constraints, introduce generalized clauses, and apply the contextual constraint replacement rule. We propose a solution to these problems by adapting to our framework various techniques developed in the field of constraint programming, partial evaluation, and abstract interpretation. In particular, we use: (i) suitable solvers for simplifying constraints, (ii) wellquasiorders for ensuring the termination...
Generating Propagation Rules for Finite Domains via Unification in Finite Algebras
 In New Trends in Constraints
, 2000
"... . Constraint solving techniques are nowadays frequently based on constraint propagation which can be interpreted as a specic form of deduction. Using constraint programming languages enhanced with constraint handling rules facilities, we can now perform constraint propagation just by applying de ..."
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Cited by 6 (0 self)
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. Constraint solving techniques are nowadays frequently based on constraint propagation which can be interpreted as a specic form of deduction. Using constraint programming languages enhanced with constraint handling rules facilities, we can now perform constraint propagation just by applying deduction rules over constraints. The idea of computing propagation rules in the particular case of small nite domains has emerged in a recent paper by K. R. Apt and E. Monfroy [1]. Due to its interest for practical applications, the integration of Finite Domains into (constraint) logic programming has been thoroughly investigated during the last decade. A possible way of integration is achieved using a unitary unication algorithm, based on the handling of Directed Acyclic Graphs to represent functions over the nite domain. We show in this paper the interest of this solver for the generation of propagation rules for nite domains. Our motivation relies on the wellestablished fact that...
A CHRG model of the ancient Egyptian grammar. Unpublished student project report
, 2002
"... This report describes and discusses the experiment of writing a grammar of ancient Egyptian, with focus on the the modelling aspect and the formalism used. A grammar or in other words a program was developed using the Constraint Handling Rules (CHR) based grammar formalism CHRGrammars (CHRG, develo ..."
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Cited by 3 (0 self)
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This report describes and discusses the experiment of writing a grammar of ancient Egyptian, with focus on the the modelling aspect and the formalism used. A grammar or in other words a program was developed using the Constraint Handling Rules (CHR) based grammar formalism CHRGrammars (CHRG, developed by Henning Christiansen). When the report was written, its writers were new to the field of Natural Language Processing (NLP) and at the same time the entering upon a relatively unexplored area: the application of NLP to ancient Egyptian. Especially with respect to the application of CHRG something new is done, since the rather new formalism have never before been used for NLP. Put simple the goal was to create an extendible and general model of ancient Egyptian grammar. It should be able to verify whether a list of ’signs ’ (i.e. representations of hieroglyphic signs in the style: A1, B15, B20) can be recognised as a correct sentence according to the model of the ancient
A CHRG Analysis of ambiguity in Biological Texts (Extended Abstract)
"... Abstract. We propose a methodology for analyzing human language sentences which can efficiently choose between alternative readings springing from the interaction between coordination and preposition phrase attachment. We present a proofofconcept in terms of an extremely succinct CHRG [3] analyzer ..."
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Abstract. We propose a methodology for analyzing human language sentences which can efficiently choose between alternative readings springing from the interaction between coordination and preposition phrase attachment. We present a proofofconcept in terms of an extremely succinct CHRG [3] analyzer for interpreting biological text titles. Our method uses expert knowledge on semantic types and compatibilities among them, as well as contextual facilities of CHRG to gain an overall view of the sentence components involved in disambiguation. 1