Schema integration in object-oriented databases

Abstract

This paper presents a formal approach to support schema integration in objectoriented databases. The basis of the approach is a subclass order, which is defined in terms of a weak subtype relation on underlying types of classes and a subfunction relation on functional forms of methods. The subclass order induces an equivalence relation and a join operator, which are used to identify and factorise class hierarchies, leading to a natural framework for integration of class hierarchies. The novelty of this paper is that both attributes and methods are used to compare classes, and that behaviour of methods is used to compare attributes, resulting in a more semantic approach towards schema integration in object-oriented databases.