A Terminological Logic with Defaults: A Definition and an Application

Abstract

In this paper we present a terminological language which includes defaults, and a definition of default subsumption based on the notion of skeptical inheritance in default reasoning. Except for the inclusion of defaults the language is limited when compared to most terminological logics. However defaults are a necessary construct in many applications and we suggest that the language presented here is a useful tradeoff between different types of expressivity We present an algorithm for classifying new concepts into the default hierarchy representing the taxonomy, and in addition an algorithm for what we call default classification, suitable for interactive reasoning about individuals. We describe a diagnosis application which has been implemented using this language and reasoning mechanisms. We present an evaluation of the diagnosis application on the basis of comparison with 63 patient protocols. We conclude that the language presented is in fact adequate for the application presented here and hypothesize that it i.s interesting for a significant group of applications. 1