A unified framework for supporting dynamic schema evolution in object databases

This paper addresses the design of an integrated framework for managing schema evolution. This framework is based on the adaptation and extension of two main schema evolution approaches, namely schema modification and schema versioning. The proposed framework provides an integrated environment to support different database evolution techniques (such as, modification and versions at the schema level, conversion, object versioning, and screening at the instance level). We introduce the concept of class/schema version pertinence enabling the database administrator to judge the pertinence of versions with regard to database applications. Finally, we propose a declarative language based on OQL, the ODMG query language, that the user can use to guide objects adaptation process when dealing with complex or application specific schema updates.