An accurate
conceptual design is the fundamental requirement for the construction of a
well-documented data mart that completely meets requirements.
Use of the
Entity-Relationship model (ERM) is quite widespread throughout companies as a
conceptual tool for standard documentation and design of relational databases.
However, Entity-Relationship schemata are hardly understood by users; besides, though the ERM is expressive enough to represent the majority of concepts necessary to data mart modeling, it is not able to highlight the distinctive features of the multidimensional model. So, Entity-Relationship schemata should not be adopted for data mart modeling.
The Dimensional Fact Model (DFM) is a conceptual model created specifically to function as data mart design support. It is essentially graphic and based on the multidimensional model. The goals of the DFM are to
- lend effective support to conceptual design;
- create an environment in which user queries may be formulated intuitively;
- make communication possible between designers and end users with the goal of formalizing requirement specifications;
- enable early testing and verification of user requirements;
- build a stable platform for logical design;
- provide clear and expressive design documentation.
These characteristics make the DFM an optimal candidate for use in real application contexts.