A Four-Valued Fuzzy Propositional Logic

Abstract

It is generally accepted that knowledge based systems would be smarter and more robust if they can manage inconsistent, incomplete or imprecise knowledge. This paper is about a four-valued fuzzy propositional logic, which is the result of the combination of a four-valued logic and a fuzzy propositional logic. Besides the nice computational properties, the logic enables us also to deal both with inconsistency and imprecise predicates in a simple way. 1 Introduction The management of uncertainty in inference systems is an important issue due to the imperfect nature of real world information. There are several fields in which this information has to do with vague concepts, i.e. concepts without clear definition. The key fact about vague concepts is that while they are not well defined, propositions involving them may be quite well defined. For instance, the boundaries of the Mount Everest are ill defined, whereas the proposition stating that the Mount Everest is the highest mountain of ...