Temporal queries and version management in XML-based document archives

By storing the successive versions of a document in an incremental fashion, XML repositories and data warehouses achieve: (i) the efficient preservation of critical information and (ii) the ability to support historical queries on the evolution of documents and their contents. In this paper, we present efficient techniques for managing multi-version document histories and supporting powerful temporal queries on such documents. Our approach consists of: (i) concisely representing the successive versions of a document as an XML document that implements a temporally-grouped data model and (ii) using XML query languages, such as XQuery, to express complex queries on the content of a particular version, and on the temporal evolution of the document elements and contents. We show that the data definition and manipulation framework of XML and XQuery can effectively support temporal models and historical queries without requiring extensions to the current standards; in fact, this approach is effective at representing and querying the histories of relational database tables, which are difficult to manage using SQL. These conclusions emerge through a number of interesting case studies presented in this paper that include W3C documents, the UCLA course catalog, and the CIA World Factbook. 2007 Published by Elsevier B.V.