For instance,
thanks to the existence of a many-to-one association between products and their
categories, the invoicing events may be grouped according to the category of the
products.
Definition 7: Given a set of dimension attributes, each tuple of their
values identifies a secondary event that aggregates all the corresponding
primary events. Each secondary event is described by a value for each
measure that summarizes the values taken by the same measure in the
corresponding primary events.
We close this section by surveying some alternative terminology used either in
the literature or in the commercial tools. There is substantial agreement on using
the term dimensions to designate the ???entry points??? to classify and identify
events; while we refer in particular to the attribute determining the minimum
fact granularity, sometimes the whole hierarchies are named as dimensions (for
instance, the term ???time dimension??? often refers to the whole hierarchy built on
dimension date). Measures are sometimes called variables or metrics. Finally, in
some data warehousing tools, the term hierarchy denotes each single branch of
the tree rooted in a dimension.
The. Dimensional. Fact.Model:............
Advanced.Modeling
The constructs we introduce in this section, with the support of Figure 4, are descriptive
and cross-dimension attributes; convergences; shared, incomplete, recursive,
0 Rizzi
Copyright ?© 2007, Idea Group Inc.
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