There has been significant work done on utilizing specialized data modeling techniques for data warehousing. In particular, the dimensional approach has been adopted to model data warehouses for a relational database. With a dimensional modeling approach, many of the traditional normalization techniques are not utilized. Instead, the model utilized a mixed approach of highly normalized portions of the model and highly denormalized parts of the model. The model is centered on two types of entities, facts and dimensions.
Facts are entities that deal with measurements or indicators.
A fact entity for a sales organization could measure revenue per month, or units sold per day. A fact for a manufacturing organization could measure defects per lot per day or units produced per week. Dimensions are entities that represent dimensional information about the facts. Dimensions are ways that the data can be sliced or viewed or segmented. Dimensions typically represent and n-leveled hierarchy such as a product hierarchy or sales organization hierarchy.