Planning and Control

TL Dean and MP Wellman Morgan Kaufmann Publishers, 1991. Google Books ISBN-10: 1558602097 ISBN-13: 978-1558602090

Impediments to universal preference-based default theories

Research on nonmonotonic and default reasoning has identified several important criteria for preferring alternative default inferences. The theories of reasoning based on each of these criteria may uniformly be viewed as theories of rational inference, in which the reasoner selects maximally preferred states of belief. Though researchers have noted some cases of apparent conflict between the preferences supported by different theories, it has been hoped that these special theories of reasoning may be combined into a universal logic of nonmonotonic reasoning. We show that the different categories of preferences conflict more than has been realized, and adapt formal results from social choice theory to prove that every universal theory of default reasoning will violate at least one reasonable principle of rational reasoning. Our results can be interpreted as demonstrating that, within the preferential framework, we cannot expect much improvement on the rigid lexicographic priority mechanisms that have been proposed for conflict resolution.

A Logic of Relative Desire (Preliminary Report)

Although many have proposed formal characterizations of belief structures as bases for rational action, the problem of characterizing rational desire has attracted little attention. AI relies heavily on goal conditions interpreted (apparently) as absolute expressions of desirability, but these cannot express varying degrees of goal satisfaction or preferences among alternative goals. Our previous work provided a relative interpretation of goals as qualitative statements about preferability, all else equal. We extend that treatment to the comparision of arbitrary propositions, and develop a propositional logic of relative desire suitable for formalizing properties of planning and problem-solving methods.