Resolving ambiguity in nonmonotonic inheritance hierarchies

Abstract

This paper describes a theory of inheritance theories. We present an original theory of inheritance in nonmonotonic hierarchies. The structures on which this theory is based delineate a framework that subsumes most inheritance theories in the literature, providing a new foundation for inheritance. • • Our path-based theory is sound and complete w.r.t. a direct model-theoretic semantics. • • Both the credulous and the skeptical conclusions of this theory are polynomial-time computable. • • We prove that true skeptical inheritance is not contained in the language of path-based inheritance. Because our techniques are modular w.r.t. the definition of specificity, they generalize to provide a unified framework for a broad class of inheritance theories. By describing multiple inheritance theories in the same “language” of credulous extensions, we make principled comparisons rather than the ad hoc examination of specific examples that makes up most of the comparative inheritance work.