Object Functional Dependencies and the Semantics of Class Extensions

We introduce the concept of object functional dependency for object oriented models, and we study consistency, satisfaction and functional implication in the context of a class extension. We then use functional implication to define the formal semantics of a class extension by a least fixpoint construction. The concepts introduced here are motivated by similar and well known concepts of the relational model. However, their definition in the context of a class extension requires a "dual" approach to the one used in object oriented models. Namely, instead of considering each object of a class extension associated to a tuple of values over the class attributes, we consider each class attribute associated to a tuple of values over the objects of the class extension. One important aspect of our work is the clear separation between the concepts of consistency and satisfaction, something that the traditional tuples-asfunctions approach of the relational model has not been able to achieve. Ano..