Direct match algorithm for production systems

Abstract

AbstractA production system is a typical tool for constructing an expert system. The Rete algorithm has been used as the condition match in the production system. The Rete algorithm features in that the condition match can executed efficiently by retaining the intermediate result of matching using the data‐flow graph (called Rete network). Efficiency is deteriorated, however, when most of the intermediate results are updated by a single recognition‐action cycle. Moreover, execution time for the condition match increases rapidly with an increase in the working memory elements. From such a viewpoint, this paper proposes a condition match algorithm wherein the intermediate result of matching is not retained, and the number of working memory tuples to be examined is reduced by connecting the common variables among the condition element. The proposed algorithm directly tries the condition match without using the Rete algorithm. The execution time does not increase so rapidly as in the Rete algorithm, but increases only slowly with the increase of the working memory elements. Consequently, the efficiency of the Rete algorithm is better when there are fewer working memory elements, and the efficiency of the proposed method is better when both the number of working memory elements and the computation cost for the condition match are increased. In other words, the proposed algorithm can handle high‐cost rules.