Soft Constraint Propagation and Solving in Constraint Handling Rules

Soft constraints are a generalization of classical constraints, which allow for the description of preferences rather than strict requirements. In soft constraints, constraints and partial assignments are given preference or importance levels, and constraints are combined according to combinators which express the desired optimization criteria. On the other hand, constraint handling rules (CHR) constitute a high‐level natural formalism to specify constraint solvers and propagation algorithms. We present a framework to design and specify soft constraint solvers by using CHR. In this way, we extend the range of applicability of CHR to soft constraints rather than just classical ones, and we provide a straightforward implementation for soft constraint solvers.

[1]  Rina Dechter,et al.  Bucket Elimination: A Unifying Framework for Reasoning , 1999, Artif. Intell..

[2]  Z. Ruttkay.  Fuzzy constraint satisfaction , 1994, Proceedings of 1994 IEEE 3rd International Fuzzy Systems Conference.

[3]  Richard J. Wallace,et al.  Partial Constraint Satisfaction , 1989, IJCAI.

[5]  Pascal Van Hentenryck,et al.  Search and strategies in OPL , 2000, TOCL.

[6]  Yan Georget,et al.  Compiling Semiring-Based Constraints with clp (FD, S) , 1998, CP.

[7]  Peter J. Stuckey,et al.  Programming with Constraints: An Introduction , 1998 .

[8]  Pascal Van Hentenryck.  Constraint satisfaction in logic programming , 1989, Logic programming.

[9]  Francesca Rossi,et al.  Semiring-based constraint satisfaction and optimization , 1997, JACM.

[10]  Michael J. Maher,et al.  Constraint Hierarchies and Logic Programming , 1989, ICLP.

[11]  D. Dubois,et al.  The calculus of fuzzy restrictions as a basis for flexible constraint satisfaction , 1993, [Proceedings 1993] Second IEEE International Conference on Fuzzy Systems.

[12]  Mats Carlsson,et al.  SICStus Prolog User''s Manual , 1993 .

[13]  Philippe Codognet,et al.  Compiling Constraints in clp(FD) , 1996, J. Log. Program..

[14]  Francesca Rossi,et al.  Semiring-based constraint solving and optimization , 1997 .

[15]  Thom W. Frühwirth,et al.  Theory and Practice of Constraint Handling Rules , 1998, J. Log. Program..

[16]  Javier Larrosa,et al.  Boosting Search with Variable Elimination , 2000, CP.

[17]  Slim Abdennadher,et al.  Essentials of Constraint Programming , 2010, Cognitive Technologies.

[18]  Thomas Schiex,et al.  Possibilistic Constraint Satisfaction Problems or "How to Handle Soft Constraints?" , 1992, UAI.

[19]  Thomas Schiex,et al.  Valued Constraint Satisfaction Problems: Hard and Easy Problems , 1995, IJCAI.