OBJECT-ORIENTED PATTERNS - LESSONS FROM EXPERT-SYSTEMS

Three benefits are typically claimed for object-oriented (OO) patterns : (i) reusing parts of the conceptual models of old implementations; ( ii) guiding the current development based on using successful previous developments; and (iii) communicating existing systems to newcomers. We will argue that a similar idea can be found in the expert systems l iterature dating from the early 1980s. The goal of KL or knowledge-lev el modelling (e.g. KADS) is to identify abstract patterns of inference that appear in many expert systems. Such abstract patterns of inferen ce and program structure, it is argued, are productivity tools for the creation of software applications, i.e. KL argues for a similar reuse benefit as OO patterns. Recently, however, an alternative view has em erged. While such abstract patterns are good fbr communications and gu idance, the reuse benefits may never be realised. Patterns may he best viewed as tools For structuring an argument, rather than recording a conclusion. (C) 1997 by John Wiley & Sons, Ltd.