An Access Mechanism for a Temporal Versioned Object-Oriented Database

Object-Oriented database systems (OODBMS) are well known for modeling complex and dynamic application domains. Typically OODBMS have to handle large and complex structured objects whose values and structures can change frequently. Consequently there is a high demand for systems which support temporal and versioning features in both objects (or database population) and schema. This paper presents a mechanism for accessing the temporal versioned objects stored in the database which supports schema versioning. The results shown here can be considered as a value-added extension of our model called TVOO described in detail in [1] and [2]. In contrast to conventional database models, in TVOO objects and classes are not physically discarded from the database after they are modified or deleted. They are time dependent and the history of the changes which occur on them are kept as Version hierarchies. Therefore our model enriches the database environment with temporal and versioning features. Also, an access mechanism which makes it possible to access any object under any schema version is defined in such a way that not only objects created under old versions of schema classes can be accessed from new versions, but also objects created by new schema class versions can be accessed from old versions of the respective class. key words: object-oriented databases, temporal databases, versioning