Object-oriented database management systems (OODBMS) are especially suited to model complex and highly dynamic application domains. In this paper, we propose a schema versioning approach which supports the dynamic change of an object-oriented database schema while it is used by running applications. Our mechanism allows to have applications working with different schema versions on top of the same single database in parallel. A flexible and parameterized approach is presented to make instances of the database accessible in different versions of a schema. In this way, it is no longer required to update all database applications at once whenever the schema is changed. Instead, the adaptation of old applications to a new schema version can be done later if this is considered advantageous.
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