A General Computational Scheme for Constraint Logic Programming

In this paper we propose a novel computational model for constraint logic programming (CLP) languages. The model provides an eecient mechanism for executing CLP programs by exploiting constraint satisfaction as a means for both solving constraints and controlling the whole computation. In the model, we separate constraint solving from the deduction procedure. Deductions over constraints are extracted from the source program and represented as a context-free grammar that encodes the way in which deduction will generate constraints to be solved. Therefore, deduction is performed abstractly at compile time. Executing the grammar generates all the constraints that need to be solved at run time. A very exible control mechanism is therefore provided by the model in terms of the information fed back from the constraint solving procedure. It is shown that the model provides a general scheme for investigating an eecient computational model for implementing constraint logic programming systems.