Using Prolog for building frog, a hybrid knowledge representation system

Abstract

FROG (FRames in ProlOG) is a Prolog based hybrid knowledge representation system which combines frames, production rules and Prolog at various levels. In this paper we shall first describe the particular technique we used for buiding the FROG system in Prolog. This technique is based on the use of apreprocessor which is able to produce the effective Prolog implementation of the system from an appropriate high level description of the knowledge of a given domain. We shall then describe the main features of the FROG system. The system supplies the knowledge engineer with a veryflexible frame structure in which each frame can contain either slots or production rules (with various kinds of inference strategies) and gives the possibility of using Prolog procedures in various places within each frame. Some hints on the Prolog implementation will also be given. Finally, the FROG high level language will be described. Both syntax and semantics of such a language are based on Prolog, thus assuring a uniform and precise description of a knowledge base. The language also allows control strategies in the system to be explicitly defined by the knowledge engineer.