Deputy Mechanisms for Object-Oriented Databases

Concepts of deputy objects and deputy classes for object-oriented databases (OODBs) are introduced. They can be used for unified realization of object views, roles and migration. The previous researches on these concepts were carried out separately, although they are very closely related. Objects appearing in a view can be regarded as playing roles in that view. Object migration is caused by change of roles of an object. Deputy objects can be used for unified treatment of them and generalization of these concepts. The schemata of deputy objects are defined by deputy classes. A set of algebraic operations are developed for deputy class derivation. In addition, three procedures for update propagation between deputy objects and source objects have been designed, which can support dynamic classification. The unified realization of object views, roles and migration by deputy mechanisms can achieve the following advantages. (1) Treating view objects as roles of an object allows them to have additional attributes and methods so that the autonomous views suitable for OODBs can be realized. (2) Handling object roles in the same way as object views enables object migration to be easily realized by dynamic classification functions of object views. (3) Generalization of object views, roles and migration makes it possible that various semantic constraints on them can, be defined and enforced uniformly.