AN OBJECT MODEL AT CONCEPTUAL LEVEL TO SUPPORT UPDATABLE VIEWS ON OBJECT-ORIENTED DATABASES

The research on view mechanisms for object-oriented databases can be c lassified into two independent issues, languages to define views and t he underlying object models. This paper presents an object model at th e conceptual level of abstraction. We call it the view class and real- world object model (V-R model). The major goal of the V-R model is int ended to support updatable views efficiently for the object-oriented d atabase systems. The V-R model elaborates a special method to describe the instance-of relationship between stored objects and classes so th at a stored object can be the instance of several classes simultaneous ly. Query results and views can be managed like classes without creati ng temporary objects or tuples since the V-R model is closed against q uery operations. In this way, updates on views can be supported easily . This paper also explores the update semantics in depth. By utilizing the specialty of the V-R model, a more eligible update translation is proposed for the updates on classes with or without inheritance relat ionships and for the updates on views. To show that the V-R model is n ot only theoretical, how to implement the V-R model and how to integra te the V-R model into an object-oriented database system are illustrat ed. (C) Elsevier Science Inc. 1996