A Formal Object-Oriented Query Model and an Algebra

Abstract

In this paper, we describe an object-oriented query model we have developed for object-oriented database management systems (OODBMSs). Our object algebra allows for the manipulation of existing objects as well as the creation of objects via the introduction of new relationships. As a result we have an object algebra that maintains the closure property in a natural way by having operands and the output from a query to have pairs of sets, a set of objects and a set of message expressions where a message expression is a sequence of messages. So, our object algebra handles objects as well as behaviour defined on them. Furthermore, our object algebra is at least as powerful as the relational algebra and the nested algebra. In fact, it is more powerful at least due to message expressions that handle both stored and derived values; hence give the user a full computational power without any need to have an embedded query language leading to impedance mismatch.