Jacek Leszczylowski, Kazimierz Subieta

Technical Aspects of Updateable Views in Object Bases

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Abstract

The paper presents briefly technical aspects of a new approach to object-oriented views. It is done in a semi-formal way based on simple, leading examples. The examples have to illustrate main features of a model. This approach relies on treating views via virtual objects, which are to have main properties of real objects such as identity, their classes and operations. These notions are meant to be building blocks to express views but are independent and may be used for other purposes, for example derived (computational) objects in a programming environment. The principle is to have all necessary constructs to be orthogonal and seamlessly combined with all other constructs of the underlying object-oriented model. This means that not only real objects can have virtual sub-objects but also virtual objects can have real sub-objects. On the other hand, the approach is supposed to be comprehensive: we want to show how to introduce the ideas into an (almost arbitrary) object-oriented model and we would like to advocate that a view in such a setting gives to a user a certain perspective of overall database/programming system in which virtual objects play a main role.

Key words: updateable views, object bases, query languages, operational semantics