"The main objective of the present proposal is to study three valued logics in connection with uncertainty management and applications in artificial intelligence. A survey of the existing three valued logics and the motivation underlying their definition will be performed; a complete study of the operations (implication, conjunction, disjunction, negation) on three values and their logical formalization pursued and applications of three valued logics investigated. The challenge is to link formal studies with applications and to arrive at a complete view on three valued logics. The proposal has a theoretical part and a more applicative one. The former is devoted to a formal study of three valued logics: already existing ones, specifically defined on three values or not, and new defined ones, starting from connectives definitions to arrive at a complete logical calculus. In the applicative part the formal systems will be applied to uncertainty management and in particular to rough sets, conditional events and NULL value management in databases. In each situation, new solutions in the form of new ways to handle three values through a proper logical system will be proposed."