You must thoroughly analyze your business data to understand and plan your business model requirements.
Planning your business model is the first step in developing a usable data model for decision support. After planning, you can begin to create your repository.
You must understand the requirements of the business model before you can determine the components of the Physical layer.
In a decision support environment, the objective of data modeling is to design a model that presents business information in a manner that parallels business analysts' understanding of the business structure. A successful model allows the query process to become a natural process by enabling analysts to structure queries in the same intuitive fashion as they would ask business questions. This model must be one that business analysts inherently understand and that answers meaningful questions correctly.
Unlike visual SQL tools such as Oracle BI Publisher, the business model defines the analytic behavior of your BI application. In contrast, the Physical layer only provides the components used to assemble a physical query mapped from business model logic.
This requires breaking down your business into several components to answer the following questions:
What kinds of business questions are analysts trying to answer?
What are the measures required to understand business performance?
What are all the dimensions under which the business operates? Or, in other words, what are the dimensions used to break down the measurements and provide headers for the reports?
Are there hierarchical elements in each dimension, and what types of relationships define each hierarchy?
After you have answered these questions, you can identify and define the elements of your business model.