In the context of regular relational databases, functional
These programs are either written by database managers dependencies have received a lot of attention, since they or ''derived'' from some declarative formulation of the capture some semantics about the data related to redun-ICs by the DBMS (this second approach is more desirdancy. Functional dependencies lead to an appropriate able, since it allows for a high-level readable expression design of a database in terms of a set of relations and of the constraints and it avoids an explicit programming). can make the checking process of integrity constraints significantly easier. For about 10 years, several propos-Different types of integrity constraints have been idenals to deal with ill-known information in database mantified among which a particular type came out very early, agement systems have been made, and extensions of along with the relational model of data (Codd, 1970): the relational data model have been proposed accord-Functional dependencies (FDs) (Bernstein, Swenson, & ingly. In this context, the idea of fuzzy functional dependency has emerged to extend the classical functional Tsichritzis, 1975), and, to a lesser extent, other dependendependency, and several definitions have been procies (multi-valued [Fagin, 1977] and join dependencies posed. In this article, an overview of these different pro- [Nicolas, 1978; Rissanen, 1978]). In fact, dependencies posals is provided, and the connection between fuzzy are ICs with a special status in the sense that they are functional dependencies and database design is disconnected with database design (and thus intervene at an cussed. In addition, some semantics and use of fuzzy functional dependencies are suggested.