Functional Dependencies

Abstract

Dependencies constitute an inherent property of database systems. They express the different ways that data are associated with each other and therefore, the semantics in relational database schemata. Functional dependence is an important property of a relation. In a relation which verifies some functional dependency, there is a functional connection between the parts of tuples. Functional dependencies can be defined like functions f: X --> Y which are mappings satisfying the conditions:

• 1 For each element x ϵ X there exists an element y ϵ Y such that f (x) = y.

• 2 For all x, x’ ϵ X: x = x’ implies f (x) = f (x’).