Abstract

. We are investigating the use of a class of logical formulas to define constraint theories and implement constraint solvers at the same time. The representation of constraint evaluation in a declarative formalism greatly facilitates the prototyping, extension, specialization and combination of constraint solvers. In our approach, constraint evaluation is specified using multiheaded guarded clauses called constraint handling rules (CHRs). CHRs define determinate conditional rewrite systems that express how conjunctions of constraints propagate and simplify. In this paper we concentrate on CHRs as an extension for constraint logic programming languages. Into such languages, the CHRs can be tightly integrated. They can make use of any hard-wired solvers already built into the host language. Program clauses can be used to specify the non-deterministic behavior of constraints, i.e. to introduce search by constraints. In this way our approach merges the advantages of constraints (eager simp...

Citations

704	Constraint Logic Programming: A Survey - Jaffar, Maher - 1994
448	Simple Word Problems in Universal Algebra - Knuth, Bendix - 1970
403	Concurrent Constraint Programming - Saraswat - 1993
308	Programming with Constraints: An Introduction - Marriott, Stuckey - 1998
86	Operational semantics and confluence of constraint propagation rules - Abdennadher - 1997
56	Confluence of conditional rewrite systems - Dershowitz, Okada, et al. - 1987
53	Commutation, transformation, and termination - Bachmair, Dershowitz - 1985
11	On confluence of Constraint Handling Rules - Abdennadher, Frühwirth, et al. - 1996
8	Logic programming by completion - Dershowitz, Josephson - 1984
5	Analyse von regelbasierten Constraintlösern - Abdennadher - 1998
3	The constraint programming working group - ACM - 1996
2	A Declarative Language for Constraint Systems: Theory and Practice of Constraint Handling Rules - Fruhwirth - 1998
1	On rewrite programs: Semantics and relationsship with PROLOG - Bonacina, Hsiang - 1992