Supporting update propagation in object-oriented databases

摘要

Objects in a database are interrelated. When an update operation is applied to an object, it may also impact on its related objects, depending on the semantics of their relationships. Current OODBMSs provide no support for update propagation but hard-coding. In this paper, we study update propagation support for generic update operations in object-oriented databases. We take a declarative approach, specifying propagation policies for each identified reference attribute in classes of an object-oriented database schema. Propagation policies for generic update propagation are well defined. However, we also discover that potential conflicts among propagation policies may occur if the policies can be arbitrarily specified by a designer. Therefore, we promote the update propagation problem to a higher level, investigating possible dependencies between objects. As such, the designer only needs to specify the dependency property for each reference attribute. Propagation policies are predefined for each type of dependency. By introducing some restrictions on an object-oriented database schema, conflict-free propagation policies can be achieved. Implementation issues for update propagation support in object-oriented database systems are also addressed.