Evolution towards, in, and beyond Object Databases

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 er ences Among the topics touched upon are extending traditional data models to become object oriented migrating existing data to not nec essarily OO databases schema extension and modi cation in a popu lated 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 al low for a formal description of most of the relevant problems Beyond presenting our own approach we try to provide a platform to solicit further discussion