Super-Key Classes for Updating Materialized Derived Classes in Object Bases

We describe data structures that allow e cient updates of materialized classes derived from relationship of classes in object bases. Materialization of derived classes reduces costs of retrievals and increases costs of updates. Costs of updates increase remarkably when several paths of objects derive the same object. If object bases satisfy the superkey condition proposed in this paper, consistencies of object bases are maintained by local navigations and the remarkable increase of the costs is avoided. Any object base can be transformed to satisfy the superkey condition by adding extra classes and their objects. In this manner, increasing redundancies allows e cient updates.