The Business Model and Mapping layer is responsible for the business rules and it depends on the Physical layer objects. The BI server is going to generate SQL statements based on the BMM layer objects. Obviously, the objects defined in this layer may positively improve the performance. We have to design all the BMM layer objects carefully. Here are the some types of the objects that are used in this layer:
Logical dimension tables
Logical fact tables
Logical table sources
Logical dimensions
Calculated measure columns
Although the BMM layer objects are transparent to the end users, one should create logical dimension and fact tables with meaningful names and use prefixes to distinguish them from each other.
Ensure that the levels of hierarchies are set to logical columns correctly. All the dimension levels should be mapped with the logical table columns. In the case of unmapped levels, business users are going to have issues...