The June 1994 workshop was held in the framework of the International School of Mathematics "G. Stampacchia." This volume includes nine invited and ten contributed papers presented at the workshop, as well as the transcript of a roundtable. Among the topics of invited papers are Choquet expected utility models, the logic of fuzzy logic, the mathematical foundations of evidence theory, prospects and problems in applying the fundamental theorem of prevision as an expert system, and revision rules for convex sets of probabilities. Annotation c. by Book News, Inc., Portland, Or.