Multiple models of physical systems - Modeling intermittent faults, inaccuracy, and tests in diagnosis

Diagnosis as a real human activity of problem solving, involves many actions and reasoning steps that seem to conflict with the use of exact, formal, and complete models of physical systems in model-based diagnosis. This paper focuses on demonstrating that some features occurring in practical diagnostic tasks, namely coping with intermittent faults, inaccurate models and observations, and testing, can be incorporated in consistency-based diagnostic systems. The basis is established by an extension to consistency-based diagnosis that enables the use of multiple models and hypothetical reasoning. It provides a sound theoretical foundation for building systems that can reflect simplifications and plausible inferences in multiple models, rather than using implicit, hard-wired heuristics, and relate the various models by logical links which clearly determine the underlying assumptions and the impact of a model shift on the diagnostic result.