Constraint Manipulation using Rewrite Rules andStrategiesCarlos

We are interested in constraint manipulation using rule-based algorithms because of the explicit distinction made in this approach between deduction rules and control. We associate actions with rewrite rules and control with strategies that establish the order of application of the inferences. This framework allows us to describe constraint handling in a very abstract way, prototype new heuristics almost by modifying only the choice of rules, prove termination in an easier and possibly partially automated way, and combine constraint solving with other computational systems. Our rst goal is to improve our understanding of the algorithms developed for handling Constraint Satisfaction Problems, once they are expressed as rewrite rules coordinated by strategies, and then to be able to propose new ones. Extending the domain of application of Rewriting Logic to constraint solving is another motivation for our work. In this paper, we formalise constraint solving as an inference process and we present a new technique for handling disjunctive constraints. We hope that this work leads the way to the design of a formalism that allows the application of the knowledge already developed in the domain of Automated Deduction, to the constraint solving process. To verify our approach we have implemented a prototype which is currently executable in the system ELAN, an interpreter of computational systems.