Views in object-oriented databases
Marc H. Scholl, Christian Laasch, Markus Tresch · KOPS (University of Konstanz) · 1990
Object-oriented database systems (ooDBSs) are supposed to offer at least the functionality available in commercial relational DBSs of today. One important consequence of this is that ooDBSs have to provide a separation of the global (conceptual) database schema from a particular task's individual external schema ("subschema"). This is more than just an "upward compatibility" argument, there are good reasons for views in ooDBSs: among them are support for multiple levels of detail, security, and authorization, and database support in a heterogeneous environment, to name just a few. In a relational DBS, views are the means by which such extemal schemata are derived from the logical database schema: a query defines the extent of the view-relation. In the relational context, views can not be freely updated. We describe an object model and query language that provides view definition capabilities and show that updating object views is much more feasible than in the case of relational views. The key property of the query language operators leading to this result is object preservation.