Data dependencies over rough relational expressions

Functional dependencies, including weighted ones, are formulated in the same manner as other constraints in a relational database based on rough sets. A tuple that belongs to a relation is accompanied by a supplementary attribute value. When a functional dependency is imposed on a relation, a compatibility degree with the functional dependency is calculated for every tuple. Whether the tuple satisfies the functional dependency is determined by comparing the compatibility degree with a supplementary attribute value. Different inference rules from the conventional ones are obtained in augmentation for functional dependencies.