62. The computer as claimed in claim 60 wherein said factual knowledge includes means for defining at least one attribute capable of having a respective value, one of the judgmental rules has a premise conditioned on the value of said attribute so that said inference engine requires the value of said attribute to apply said rule, said plurality of discrete control blocks includes at least one determination control block defining a predetermined method for determining a value for said attribute, and said language interpreter includes means for interrupting execution of said procedural language to execute the procedural langauge statements in the determination control block when said inference engine applies said rule and requires the determination of a value for said attribute.
60. The computer as claimed in claim 59, wherein said separate portion of said knowledge base encoding said control knowledge comprises a plurality of discrete control blocks, each control block including statements in said imperative procedural language, said procedural language including separate statements to ask the user a question and obtain a responsive answer, apply a specified set of said judgmental rules, display to the user the conclusions of the rules applied, and to execute another specified control block.