This means to choose
to represent either each version of the whole document or only the part of the
new version which is different from the previous one, and to understand how
to represent the time dimension related to the version time.
??? Querying.successive.versions.of.documents.stored.in.a.data.warehouse:.
In this context it could be useful to query by considering the valid time of
information, or the valid version of a document, or a particular past version,
or by considering both time dimensions. In this case the problems are related
to the study of suitable temporal clauses allowing the user to express temporal
conditions on different time dimensions, that is, version time dimension,
document valid time. For example, the user could be interested in retrieving
the evolution of a portion of the document, or in retrieving valid data. In the
former case the user would query the successive versions of a document,
while in the latter case the user would query the present (valid) version of the
document. Moreover, the user would like to query a given past version of the
document.
Conclusion
In this chapter we described a graph-based data model to represent semistructured
data warehouse by considering the valid time dimension. This approach allows one
Temporal Semistructured Data Models and Data Warehouses 2
Copyright ?© 2007, Idea Group Inc.
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