A Near-Horn Prolog for Compilation

Near-Horn Prolog is a logic programming language which extends Prolog to handle non-Horn clauses. It was designed with the goal of minimizing the performance loss for programs with very few non-Horn clauses, while preserving the Prolog format. In this paper, we present a version of near-Horn Prolog that provides a stronger proof system than used by previous near-Horn procedures, and takes advantage of the preprocessing capability of compilers to reduce the accompanying performance penalty. In fact, for a sizable class of non-Horn programs the added inference rule strength incurs no performance penalty at all. In addition to describing this variant, called Inheritance near-Horn Prolog, we prove its soundness and (classical) completeness.