The considered change operations are delete, insert, and update.
In Wang et al. (2005), the authors describe an approach to store and query the history
of XML evolving document. In particular, they compute the difference between
the successive versions of a document, and represent the history of the document
by timestamping and temporally grouping the deltas. In this way, a multiversion
document is managed as a unit and its successive versions are represented by the
delta changes between versions. This approach makes it possible to support complex
historical queries on the evolution of the document and its elements, by using Xquery
(World Wide Web Consortium, 2005b), the standard query language of XML.
In B?™bel et al. (2004), the authors propose a multiversion data warehouse that is
capable of handling changes in the schema structure as well as simulating alternative
business scenarios useful to predict trends by means of the what-if analysis. At
this aim, the authors propose two different kinds of versions: real versions, which
handle changes made to the external data sources, and alternative versions, which
handle changes made by a user for the purpose of applying the what-if analysis.
Several alternative versions can be created from a real version. Alternative versions
can be created also to simulate changes in the structure of a data warehouse schema.
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