Reifying Global Constraints

Global constraints were introduced two decades ago as a means to model some core aspects of combinatorial problems with one single constraint for which an efficient domain filtering algorithm can be provided, possibly using a complete change of representation. However, global constraints are just constraint schemas on which one would like to apply usual constraint operations such as reification, i.e. checking entailment, disentailment and negating the constraint. This is currently not the case in state-of-the-art tools and was not considered in the global constraint catalog until recently. In this paper, we propose a general framework for reifying global constraints and apply it to some important constraints of the catalog, such as the cumulative constraint for instance. We show that several global constraints that were believed to be hard to negate can in fact be efficiently negated, and that entailment and disentailment can be efficiently tested. We also point out some new global constraints that are worth studying from this point of view and provide some performance figures obtained with an implementation in Choco.Les contraintes globales ont été introduites il y a une vingtaine d'années afin de modéliser certains aspects centraux des problèmes combinatoires avec une seule contrainte dotée d'un algorithme de filtrage efficace, au besoin via un changement complet de représentation. Cependant, les contraintes globales ne sont que des schémas de contraintes sur lesquelles on souhaiterait pouvoir appliquer les opérations usuelles des contraintes comme la réification, ce qui suppose de tester l'implication et de nier la contrainte. Ceci n'est pas le cas dans les outils de l'état de l'art et n'a été considéré que récemment dans le catalogue des contraintes globales. Dans cet article nous proposons un cadre général pour réifier les contraintes globales, et l'appliquons aux principales contraintes du catalogue, comme par exemple la contrainte cumulative. Nous montrons que plusieurs contraintes réputées difficiles à nier peuvent l'être efficacement, et que l'implication peuvent être testée efficacement. Nous montrons aussi que de nouvelles contraintes globales vaudraient la peine d'être étudiées de ce point de vue, et fournissons une évaluation préliminaire des performances obtenues avec une implémentation en Choco

Proceedings of Sixth International Workshop on Unification

Swiss National Science Foundation; Austrian Federal Ministry of Science and Research; Deutsche Forschungsgemeinschaft (SFB 314); Christ Church, Oxford; Oxford University Computing Laborator

Entailment and Disentailment of Order-Sorted Feature Constraints

LIFE uses matching on order-sorted feature structures for passing arguments to functions. As opposed to unication which amounts to normalizing a conjunction of constraints, solving a matching problem consists of deciding whether a constraint (guard) or its negation are entailed by the context. We give a complete and consistent set of rules for entailment and disentailment of order-sorted feature constraints. These rules are directly usable for relative simplification, a general proof-theoretic method for proving guards in concurrent constraint logic languages using guarded rules

Proceedings of CSCLP 2007: Annual ERCIM Workshop on Constraint Solving and Constraint Logic Programming

Ce fichier regroupe en un seul document l'ensemble des articles acceptés pour la conférence CSCLP 2007Constraints are a natural way to represent knowledge, and constraint programming is a declarative programming paradigm that has been successfully used to express and solve many practical combinatorial optimization problems. Examples of application domains are scheduling, production planning, resource allocation, communication networks, robotics, and bioinformatics. These proceedings contain the research papers presented at the 12th International Workshop on Constraint Solving and Constraint Logic Programming (CSCLP'07), held on June 7th and 8th 2007, at INRIA Rocquencourt, France. This workshop, open to all, is organized as the twelfth meeting of the working group on Constraints of the European Research Consortium for Informatics and Mathematics (ERCIM). It continues a series of workshops organized since the creation of the working group in 1997, that have led since 2002 to the publication of a series of books entitled ”Recent Advances in Constraints” in the Lecture Notes in Artificial Intelligence, edited by Springer-Verlag. In addition to the contributed papers collected in this volume, two invited talks were given at CSCLP'07, one by Gilles Pesant, Ecole Polytechnique de Montreal, Canada, and one by Jean-Charles R égin, ILOG, France. The editors would like to take the opportunity to thank all the authors who submitted a paper, as well as the reviewers for their helpful work. CSCLP'07 has been made possible thanks to the support of the European Research Consortium for Informatics and Mathematics (ERCIM), the Institut National de la Recherche en Informatique et Automatique (INRIA) and the Association for Constraint programming (ACP)

Entailment and Disentailment of Order-Sorted Feature Constraints

LIFE uses matching on order-sorted feature structures for passing arguments to functions. As opposed to unification which amounts to normalizing a conjunction of constraints, solving a matching problem consists of deciding whether a constraint (guard) or its negation are entailed by the context. We give a complete and consistent set of rules for entailment and disentailment of order-sorted feature constraints. These rules are directly usable for relative simplification, a general proof-theoretic method for proving guards in concurrent constraint logic languages using guarded rules. 1 Introduction LIFE [5, 4] extends the computational paradigm of Logic Programming in two essential ways: ffl using a data structure richer than that provided by first-order constructor terms; and, ffl allowing interpretable functional expressions as bona fide terms. The first extension is based on /-terms which are attributed partially-ordered sorts denoting sets of objects [1, 2]. In particular, /-terms..