Abstract: A definition-based expert system and expert system shell. The expert system shell creates a knowledge base consisting of terms and their definitions, the definitions making up a hierarchy of definitions in which each definition depends only on terms defined at lower levels in the hierarchy or on term-independent values. Expert responses are obtained from the system by evaluating the terms. When a term is evaluated, all of the term-independent values and the values of all of the terms in its definition are obtained. The definitions include operators specifying operations which are to be performed when the defined term is evaluated. The operators include causing other systems operable in the digital computer system in which the expert system is operating to operate. The definitions further include table operators. Base table operators define terms representing tables and columns in the tables and permit loading of the tables.

Abstract: An expert system shell and expert systems created thereby. The expert system shell creates a knowledge base consisting of terms and their definitions, the definitions making up a hierarchy of definitions in which each definition depends only on definitions at lower levels in the hierarchy or on values obtained from sources external to the knowledge base. The expert system shell creates the knowledge base by asking the expert to define a given term and then asking him to define all undefined terms which appear in the definition of the given term. Because the hierarchy is created in this fashion, the definitions are guaranteed to be complete and non-contradictory. Expert systems created using the expert system shell employ an inferencing engine which determines the value of a given term by evaluating its definition. In the course of the evaluation, the definitions of terms required to define the given term are evaluated and external values required for the evaluation of the definitions are obtained.