A dimesional model typically contains the same information as an E/R model but packages the data differently to that of an normal transactional system (e.g. SAP, Oracle Financials). The data structure in a dimensional model are normally modelled to allow using three key principles:

• Ease of user understanding
• Query Performance
• Ease of adaption to change without major impact

The dimensional model has a number of key components, some of which are listed below.

Dimensions are used to describe attributes of the main information table (also known as the fact tables).

Fact tables hold the main information in each dimensional model. The information in the fact table relates to the measurements that are useful / required by the business. A fact is usually of one of three types:

• Numeric
• Addative