On the semantics of inheritance networks

Abstract

A semantics for inheritance reasoning is presented which allows both strict and defeasible knowledge to be represented. The approach proposed considers the semantics as consisting of two parts: the content theory which describes the knowledge about the world and a ‘process model’ which explains how the knowledge in the network is processed. Each process model is expressed by an algorithm which, given two sets of properties for each class or individual, computes a new set of properties. It is argued that the ‘clash of intuitions’ which appears in the literature on inheritance reasoning, is a clash of process models, as, in certain situations, different process models give different meaning to the links of a network. An attempt is also made to explain the instability of an inheritance reasoning system. It is argued that instability should not be surprising if the extra meaning that the process model assigns to a network is taken into account. This is because, in certain process models, no link in a network is considered as redundant. Some general questions on inheritance reasoning are finally raised. © 1992 Taylor and Francis Ltd.