There is a manifold of meanings we could associate with the term \evolution" in the database arena. This paper tries to categorize some of these into a unique framework, showing similarities and di erences. Among the topics touched upon are: extending traditional data models to become \object-oriented", migrating existing data to (not necessarily OO) databases, schema extension and modi cation in a populated database, integration of federated systems, and the use of \external services" to enrich DBMS functionalities. The following are presented in more detail: rst, we describe the necessity of object evolution over time second, we discuss schema evolution and third, we present evolutionary database interoperability by identifying di erent coupling levels. A few basic mechanisms, such as views (derived information) and a uniform treatment of data and meta data, and type and/or class hierarchies, allow for a formal description of (most of) the relevant problems. Beyond pre...
Marc H. Scholl, Markus Tresch