Business Model & Mapping Layer

This layer helps to implement business logic on the tables. The tables in this layer are called as logical tables whereas tables in physical layer are physical tables. Each logical table have one or more source of the physical table/view or in some cases logical table itself. Fetching data from physical column will be always faster than fetching from logical column, but with physical tables we do not have enough feasibility to implement the logic hence the logical tables.

It is best practice to join tables in BMM layer using Complex join. Since we may have multiple sources for a single logical table it would be easier for the BI server to fetch data.

To create new BMM RC(right click) anywhere in the layer and select New Business Model. Give the appropriate name and drag/copy the tables to new bmm from physical layer. After the tables are imported, the dimension tables should appear in white and facts in yellow by default. To create joins between two tables RC on two tables selected go to business model diagram > selected objects > select complex join at top on new window > drag from dim (dimension) table to fact.

It is the best practice to have hierarchies created for all the dimension tables although not required. Hierarchy created in bmm layer helps users to drill down in the reports, example: country>state>city. Drill down is the option in reports to make state appear in a report when country is clicked.