Model-Based Diagnostics Using Hints

Abstract It is often possible to describe the correct functioning of a system by a mathematical model. As long as observations or measurements correspond to the predictions made by the model, the system may be assumed to be functioning correctly. When, however, a discrepancy arises between the observations and the model-based predictions, then an explanation for this fact has to be found. The foundation of this approach to diagnostics has been laid by Reiter (1987). The explanations generated by his method, called diagnoses, are not unique in general. In addition, they are not weighed by a likelihood measure which would make it possible to compare them. We propose here the theory of hints { an interpretation of the Dempster-Shafer Theory of Evidence { as a very natural and general method for model-based diagnostics (for an introduction to the theory of hints, see Kohlas, Monney (1990)). Note that Peng, Reggia (1990) and DeKleer, Williams (1987) also discuss probabilistic approaches to diagnostic problems. Research supported by grants No. 21-30186.90 and 21-32660.91 of the Swiss National Foundation for Research, Esprit Basic Research Activity Project DRUMS II (Defeasible Reasoning and Uncertainty Management).