leff%smu@RELAY.CS.NET (11/12/86)
Dr. Benjamin Kuipers, Qualitative Reasoning About Mechanisms 10:00 AM, Friday, 7 November 1986 The first generation of diagnostic expert system is based on a simple model of knowledge: weighted links between observations and diagnoses. Experience with these systems has revealed a number of limitations in their performance due to the fact that they do not understand the mechanism by which a particular fault causes the associated observations. Recently developed methods for qualitative reasoning about these underlying mechanisms show promise of being able to extend the understanding, and hence the power, of diagnostic systems. The fundamental inference in qualitative reasoning derives the behavior of a mechanism from a description of its structure. Since both structure and behavior are represented in qualitative terms, this is essentially a qualitative abstraction of differential equations. I will derive in detail the QSIM approach to qualitative reasoning, and demonstrate a medical example in which QSIM predicts the behavior of a healthy mechanism, the "broken" mechanism corresponding to a particular disease, and the response of that broken mechanism to therapy.