Temporal queries in XML document archives and web warehouses

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 of supporting 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 in: (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 their contents. We show that the data definition & manipulation framework of XML & XQuery can support temporal models and historical queries significantly better than the traditional framework of Relational Tables & SQL. To demonstrate this point, we investigate how to express complex queries on the history of relational tables published as XML data.