Automated circuit diagnosis using first order logic tools

While numerous diagnostic expert systems have been successfully developed in recent years, they are almost uniformly based on heuristic reasoning techniques (i.e., shallow knowledge) in the form of rules. This paper reports on an automated circuit diagnostic tool based on Reiter's theory of diagnosis. In particular, this is a theory of diagnosis based on deep knowledge (i.e., knowledge based on certain design information) and using first order logic as the representation language. The inference mechanism which is incorporated as part of the diagnostic tool is a refutation based theorem prover using rewriting systems for Boolean algebra developed by Hsiang. Consequently, the diagnostic reasoning tool is broadly based on Reiter's model, but incorporates complete sets of reductions for Boolean algebra to reason over equational descriptions of the circuits to be analyzed. The refutational theorem prover uses an associative commutative identity unification algorithm described by Hsiang, but requires additional focusing techniques in order to be appropriate for diagnosing circuits. A prototype version of the mainline diagnostic program has been developed, and has been successfully demonstrated on several small but nontrivial combinational circuit examples.