Knowledge Modeling and Reusability in ExClaim

Abstract

This paper presents ExClaim, a hybrid language for knowledge representation and reasoning. Originally developed as an operationalization language for the KADS knowledge based systems (KBS) development methodology, ExClaim has a meta-level architecture: it structures the knowledge on three levels, namely the domain, inference and task level. An extension of a description logic is used for implementing the domain level. The inference and task levels are general logic programs integrated with the domain level by means of upward and downward reflection rules which describe the automatic domain operations performed whenever arguments of inferences or tasks are accessed. Inferences and tasks support non-deterministic reasoning, which in turn requires a non-monotonic domain level. Description logics offer a set of inference services (some not available in other knowledge representation languages) which are extremely useful in knowledge modeling. Such inference services include domain-level deduction, semantic consistency verification and automatic classification of concepts. We argue that such validation and verification facilities are important in assisting a knowledge engineer in developing models. These models are reusable due to the layered architecture as well as to the possibility of writing generic inferences using a reified membership relation.