KSL-87-19

The Relationship between Decision Theory and Default Reasoning

Reference: Langlotz, C. P. & Shortliffe, E. H. The Relationship between Decision Theory and Default Reasoning. Working Paper, February 1987, 1987.

Abstract: Decision theory and nonmonotonic logics are both formalisms that can be used to describe the process of planning under uncertainty. A simple logical correspondence between nonmonotonic logics and decision theory indicates that planning via default reasoning is composed of two decision-theoretic concepts: likelihoods and utilities. Because utilities represent problem-specific goals, and therfore vary with changes in the planning situation, we argue that default reasoning is problem-dependent. We present and discuss examples of the following lessons from this decision-theoretic view of nonmonotonic reasoning: (1) Nonmonotonic logics do not retain the domain-independent characteristics of classical (monotonic) logic. (2) Because certain programming paradigms (e.g., frame-based iheritance, nonmonotonic logics) are inherently problem-specific, they may be inappropriate to employ in the construction of "common sense" knowledge bases. The implications of these conclusions is considered for several current artificial intelligence research issues.

Notes: 16 pages.


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