Elaine.Atkinson@A.CS.CMU.EDU.UUCP (12/01/86)
SPEAKER: Richmond Thomason, University of Pittsburgh TITLE: "Issues in the design of nonmonotonic inheritance systems" DATE: Thursday, December 4 TIME: 4:00 p.m. PLACE: Adamson Wing, Baker Hall ABSTRACT: Early attempts at combining multiple inheritance with exceptions were based on straightforward extensions to tree- structured inheritance systems, and were theoretically unsound. Two well-know examples are FRL and NETL. In The Mathematics of Inheritance Systems (TMOIS), Touretzky described two classes of problems that these systems cannot handle. One involves reasoning with true but redundant assertions; the other involves ambiguity. The substance of TMOIS was the definition and analysis of a theoretically sound multiple inheritance sytem, along with some inference algorithms based on parallel market propagation. Now, however, we find that there appear to be other definitions for inheritance that are equally sound and intuitive, but which do not always agree with the system defined in TMOIS. In this presentation we lay out a partial design space for sound inheritance systems and describe some interesting properties that result from certain strategic choices of inheritance definitions. The best way to define inheritance -- if there is one best way -- may lie somewhere in this space, but we are not yet ready to say what it might be.