A Set - Oriented Method De nition Language for

In this paper we propose a set-oriented rule-based method deenition language for object-oriented databases. Most existing object-oriented database systems exploit a general purpose imperative object-oriented programming language as method deenition language. Because methods are written in a general-purpose imperative language, it is diicult to analyze their properties and to optimize them. Optimization is important when dealing with large amount of objects as in databases. We therefore believe that the use of an ad-hoc, set-oriented language can ooer some advantages, at least at a speciication level. In particular, such a language can ooer an appropriate framework to reason about method properties. In this paper, besides deening a set-oriented rule-based language for method deenition, we formally deene its semantics, addressing the problems of inconsistency and non-determinism of set-oriented updates. Moreover, we characterize some relevant properties of methods, such as connicts among method speciications in sibling classes and behavioral reenement in subclasses, in the framework of the proposed language.