Production systems are an established method for encoding knowledge in an expert system. In production systems, it's an important problem how to deal with expensive productions. We had proposed three methods for dealing with expensive productions using the expression method of direct-product instansiation. The evaluations of these methods, however, have reported on only simulations. In this paper, we evaluate three methods we have proposed using knowledge base, and classify a type of expensive productions suited for each expression method of direct-product instansiation.
