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Abstract : |
This paper addresses the design of a schema evolution framework enabling an efficient management of object versions. This framework is based on the adaptation and extension of two main schema evolution approaches, that is the approaches based on schema modification and those based on schema versioning. The framework provides an integrated environment to support different levels of adaptation (such as, modification and versioning at the schema level, conversion, object versioning, and emulation at the instance level). In addition, we introduce the concept of class/schema version pertinence enabling the database administrator to judge the pertinence of versions with regard the application programs. Finally, we provide operations for immediate refreshing of a database to enable an efficient manipulation of versions by a large number of application programs., |
