A Feature-Based Constraint System for Logic Programming with Entailment

and the constraints of FT are finer grained and of different ex-pressivity. The basic notion of FT are functional attributes called features, which provide for record-like descriptions of data avoiding the overspecification intrinsic in Herbrand's constructor-based descriptions. The feature tree structure fixes an algebraic semantics for FT. We will also establish a logical semantics, which is given by three recursive axiom schemes fixing the first-order theory FT. FT is a constraint system for logic programming, providing a test for unsatisfiability, and a test for entailment between constraints, which is needed for advanced control mechanisms. The two major technical contributions of this paper are (1) an incremental entailment simplification system that is proved to be sound and complete, and (2) a proof showing that FT satisfies the so-called " independence of negative constraints. "