ptimally Efficient Inference Syste

This paper describes a knowledge representation and reasoning system that performs a limited but interesting class of inferences over a restricted class of first-order sentences with optimal eticiency. The proposed system can answer yes-no as well as w/z-queries in time that is only proportional to the Zength of the shortest derivation of the query and is independent of the size of the knowledge base. This work suggests that the expressiveness and the inferential ability of a representation and reasoning systems may be limited in unusual ways to arrive at extremely efficient yet fairly powerful knowledge based systems.