A Framework for Schema Evolution by Meta Object Manipulation

In this paper we address the problem of schema evolution in object-oriented database systems. Most currently available database prototypes either completely lack schema evolution facilities, or ooer a restricted set of special purpose schema evolution operators supporting simple schema changes. Our approach is diierent. We consider schema objects as objects like others and have the meta schema fully available at run-time. Thus any operator of our object manipulation and query algebra can be applied to meta objects in the same way as they are used for data objects. We discuss the additional problems that arise when treating schema objects as normal objects and making the algebra work on the meta schema as well. Furthermore, we overview how to solve these problems on diierent levels of implementing schema evolution.