Domain independent shell for building a diagnostic expert system

An application shell providing a domain-independent diagnostic problem solver, comprising:

• knowledge base means including,
• (a) a plurality of failure mode schemata arranged in a causal hierarchy from observable failure modes to failure modes having a repair procedure;
• (b) a plurality of rule schemata related to certain of said failure mode schemata;
• (c) a plurality of datum schemata for gathering data about the system under investigation, said information being used to determine the applicability of said rule schemata;
• and
• (d) a plurality of repair procedure schemata each being related to one of said failure mode schemata having a repair procedure;
• and problem solver means for forward chaining through said knowledge has means to reach conclusions about said failure mode schemata and for backward chaining through said knowledge base means based on said rules, said conclusions, and the hierarchical arrangement of said failure mode schemata so as to change the focus from one failure mode schema to another failure mode schema deeper within the hierarchical arrangement without focusing upon any intermediate schemata to thereby locate an appropriate repair procedure schema.