Different models of fuzzy logic programming with fuzzy unification (towards a revision of fuzzy databases)

The aim of the paper is to show relationships between different formalisms for handling uncertainty in logic programming, knowledge based systems and deductive databases. Namely, we show that our model of fuzzy logic programming has the same expressive power as annotated logic programs with restricted continuous semantics. Features of fuzzy unification are achieved by extending the rule base by axioms of equality with fuzzy similarities. This induces a new fuzzy relational algebra. Our procedural semantics enables us to estimate truth values of the answers during the computation. Using this, we introduce a model with threshold computation and another for finding the best answer with prescribed precision tolerance.