The issues of schema evolution and temporal object models are generally considered to be orthogonal and are handled independently. However, to properly model applications that need incremental design and experimentation, the evolutionary histories of the schema objects should be traceable rather than corrective so that historical queries can be supported. In this paper we propose a method for managing schema changes, and propagating these changes to object instances by exploiting the functionality of a temporal object model. The result is a uniform treatment of schema evolution and temporal support for many object database management systems applications that require both.

The conceptual schema (intention) and raw data (extension) are evolving entities which require adequate support for past, present and even future versions. Temporal Databases supporting schema evolution were developed with the aim of satisfying this need. The support for schema versioning raises two complex subjects: the storage of the several schema versions and their associate data, and the processing of queries that involve more than one schema version. The main objective of this work is to analyse the second aspect in order to propose a strategy for answering those queries. In an environment supporting schema versioning the complete history of schema evolution is kept. In many occasions it can be necessary to query the database's structure, so this work proposes an extension to the temporal query language TSQL2 in order to support queries to intentional data.

XML is today a standard for manipulating semistructured data.