Constraint logic programming with hereditary Harrop formulas

Abstract

Constraint logic programing (CLP) and hereditary Harrop formulas (HH) are two well-known ways to enhance the expressivity of Horn clauses. In this paper, we present a novel combination of these two approaches. We show how to enrich the syntax and proof theory of HH with the help of a given constraint system, in such a way that the key property of HH as a logic programming language (namely, the existence of uniform proofs) is preserved. We also present a procedure for goal solving, showing its soundness and completeness for computing answer constraints. As a consequence of this result, we obtain a new strong completeness theorem for CLP that avoids building disjunctions of computed answers, as well as a more declarative formulation of a known completeness theorem for HH