The 10 Essential Rules of Dimensional Modeling

http://intelligent-enterprise.informationweek.com/showArticle.jhtml?articleID=217700810&pgno=1


The 10 Essential Rules of Dimensional Modeling
By Margy Ross

Rule #1: Load detailed atomic data into dimensional structures.

Carregar sempre o dado mais detalhado. Pois o usuario nao pode viver sem os detalhes.
Assim os dados podem ser sumarizados.

Rule #2: Structure dimensional models around business processes.

Business processes are the activities performed by your organization; they represent measurement events, like taking an order or billing a customer. Business processes typically capture or generate unique performance metrics associated with each event. These metrics translate into facts, with each business process represented by a single atomic fact table. In addition to single process fact tables, consolidated fact tables are sometimes created that combine metrics from multiple processes into one fact table at a common level of detail. Again, consolidated fact tables are a complement to the detailed single-process fact tables, not a substitute for them.

Rule #3: Ensure that every fact table has an associated date dimension table.

Obviamente. O grao deve ser um dia. As vezes multiplas chaves estrangeiras sao representadas em uma tabela fato.

Rule #4: Ensure that all facts in a single fact table are at the same grain or level of detail.

Rule #5: Resove many-to-many relationships in fact tables.

Rule #6: Resolve many-to-one relationships in dimension tables.

Rule #7: Store report labels and filter domain values in dimension tables.

Rule #8: Make certain that dimension tables use a surrogate key.

Rule #9: Create conformed dimensions to integrate data across the enterprise.

Rule #10: Continuously balance requirements and realities to deliver a DW/BI solution that's accepted by business users and that supports their decision-making.