Fuzzy functional dependencies and redundancy elimination

In the context of regular relational databases, functional dependencies have received a lot of attention, since they capture some semantics about the data related to redundancy. Functional dependencies lead to an appropriate design of a database in terms of a set of relations and can make the checking process of integrity constraints significantly easier. For about 10 years, several proposals to deal with ill-known information in database management systems have been made, and extensions of the relational data model have been proposed accordingly. In this context, the idea of fuzzy functional dependency has emerged to extend the classical functional dependency, and several definitions have been proposed. In this article, an overview of these different proposals is provided, and the connection between fuzzy functional dependencies and database design is discussed. In addition, some semantics and use of fuzzy functional dependencies are suggested.