This volume comprises the proceedings of the FirstAll-Berlin Workshop on Nonclassical Logics and InformationProcessing, held at the Free University of Berlin, November9-10, 1990.The scope of the ten papers in the volume is broad, coveringvarious different subfields of logic - particularlynonclassical logic - and its applications in artificialintelligence. The papers are grouped according to the fourmajor topics that emerged at the meeting: modal systems, logic programming, nonmonotonic logics, and proof theory.The classification is only a rough guide since the fourareas overlap considerably.

The book presents a thoroughly elaborated logical theory of generalized truth-values understood as subsets of some established set of (basic) truth values. After elucidating the importance of the very notion of a truth value in logic and philosophy, we examine some possible ways of generalizing this notion. The useful four-valued logic of first-degree entailment by Nuel Belnap and the notion of a bilattice (a lattice of truth values with two ordering relations) constitute the basis for further generalizations. By doing so we elaborate the idea of a multilattice, and most notably, a trilattice...