Identification, genericity and consistency in object-oriented databases

Abstract

It is claimed that object-oriented databases overcome many of the limitations of the relational data model especially by generalizing the notion of object identification. A clear distinction between objects and values turns out to be essential for the object-oriented approach whereas the relational model is based exclusively on values. Since, however, value uniqueness within scopes is a quite natural constraint for a wide class of applications, identification by value is also of interest for object-oriented datamodels.

Hence, in this paper we concentrate on those classes where the extents are completely representable by values. We formalize some basic concepts of object-oriented databases and show that the finiteness of a database and the existence of finitely representable recursive types are sufficient to decide value-representability.

Another advantage of the relational approach is the existence of structurally determined canonical update operations. We show that this property can be carried over to object-oriented datamodels iff classes are value-representable. Moreover, in this case database consistency with respect to implicitly specified referential and inclusion constraints will be automatically preserved.

This work has been supported in part by research grants from the E.E.C. Basic Research Action 3070 FIDE: “Formally Integrated Data Environments”.