Functional dependencies in relational expressions based on or-sets

Partial functional dependencies, functional dependencies accompanied by a factor, are examined in a relational database based on or-sets. The partial functional dependencies are dealt with under tuples having their belongingness degree to a relation. Whether a functional dependency accompanied by a factor holds in a relation is determined by comparing the factor with to what degree the relation satisfies the functional dependency. Inference rules, similar to Armstrong's axioms in the conventional relational databases, are obtained. Thus, we can discover another functional dependencies related with a partial functional dependency by using the inference rules.