This paper deals with computer system diagnosis that is performed by a system itself, rather than by an outside mechanism. The devices performing the diagnosis and the devices communicating diagnostic information are included in the system model and may be potentially faulty. This paper differs from previous work in several ways. A more general diagnostic model is used that permits analysis of a larger class of systems, and the diagnostic goals are more closely matched to realistic self-diagnosis problems. In addition, there are differences in assumptions regarding test invalidation and effects of faults on communication that produce greater self-diagnosibility while accurately modeling faulty system behavior.

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.