is prohibited.
The. Dimensional. Fact.Model:............
Basic.Modeling
In this chapter we focus on an ad hoc model called the dimensional fact model. The
DFM is a graphical conceptual model, specifically devised for multidimensional
modeling, aimed at:
??? Effectively supporting conceptual design
??? Providing an environment on which user queries can be intuitively expressed
??? Supporting the dialogue between the designer and the end users to refine the
specification of requirements
??? Creating a stable platform to ground logical design
??? Providing an expressive and non-ambiguous design documentation
The representation of reality built using the DFM consists of a set of fact schemata.
The basic concepts modeled are facts, measures, dimensions, and hierarchies. In
the following we intuitively define these concepts, referring the reader to Figure 3
that depicts a simple fact schema for modeling invoices at line granularity; a formal
definition of the same concepts can be found in Golfarelli et al. (1998).
Definition 1: A fact is a focus of interest for the decision-making process;
typically, it models a set of events occurring in the enterprise world. A
Figure 3. A basic fact schema for the INVOICE LINE fact
Conceptual Modeling Solutions for the Data Warehouse
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