A Sound Semantics for a Similarity-Based Logic Programming Language

Bousi similar to Prolog is an extension of the standard Prolog language aiming at to make more flexible the query answering process and to deal with vagueness applying declarative techniques. In this paper we precise a model-theoretic semantics for a pure subset of this language. Next, for the first time, we define a notion of correct answer which provides a declarative description of the output of a program and a goal in the context of a similarity relation. Afterwards, we recall both the WSLDresolution principle and a similarity-based unification algorithm which is the basis of its operational mechanism and then we prove the soundness of WSLD-resolution.