Diagnosis of Systems with Asymmetric Invalidation

This paper is concerned with system diagnosis through analysis of a set of diagnostic test results. It is assumed that a faulty unit may cause one or more tests on a good unit to fail, but may not cause tests on faulty units to pass (asymmetric invalidation). The system model employed is quite general; each test may be invalidated by any one of a set of units, and each test may completely test more than one unit. Conditions for diagnosability with and without repair are determined. Exact methods, as well as simpler approximate methods, are proposed for determining diagnosability and for performing diagnosis. The theory is extended to include diagnosis "by part" (where a part is a set of units). Several illustrative examples are included.