Issues in the design and implementation of views in object-oriented databases

Summary form only given. Views have traditionally been a mechanism for coordinating access to shared data in a database. View definition schemes in relational databases have aimed at consistency with the conceptual model and the use of a limited view specification language that allows efficient and unambiguous translation of view updates. These goals are equally applicable to object-oriented databases (OODBs). Consequently, it makes sense to model views in OODBs as objects themselves. OODBs differ from relational databases in that they have notions of classes and instances, and allow nesting of both classes and instances. Thus the underlying theory of the object-oriented data model is graph based, in contrast to the relational theory, which is set based. Object-oriented views can be thought of as graph transformations applied to class or instance graphs in the underlying database. Depending on the nature of the underlying objects, views can be class-lattice views or complex object views. The exact set of graph transformations that can be applied to class or instance graphs needs to be limited to allow views to be virtualizable for querying purposes