The design process starts with a report or business requirement and works back creating or adding to data models. Once that is complete, the ETL (extract, transform, load) processes are designed. The ETL processes specify how the data is moved through the system from OLTP (online transaction processing) to end report.
A business requirement for reporting is formalized by drawing a logical user model. For example, a logical model depicting the cube representation of client ages could be drawn to illustrate the outcome of this reporting requirement. A user model captures the end user's model or view of the data required.
User models help to determine the structure of the data marts. Drawing the user model involves picking out the measures or facts from the reporting requirement and the dimensions that the measure is sliced by. The user model should also identify the level of granularity required. The granularity is very important, as it determines what and how much data is captured.