OBIEE 11g : Basics of BMM Layer

Business model and mapping layer is all about designing the star schema from the physical layer. But that’s not as simple as it sounds. It is also where you define or we can say guide the BI server to use

• Preferred join condition
• Preferred physical table
• Logical level for aggregation
• Hierarchy 
• Arithmetic operations
• Where clause
• Fragmentation
• Sorting order etc

All these things combined together will give you the desired level of effectiveness and if such standards are not followed OBIEE is nothing but a simple query generation tool.

The above picture is of a business model named “Usage Tracking” with four Hierarchies and 5 logical tables.

Each has its features and operations of its own. BMM layer can only contain start schema and all the dimensions should be connected to one or the other fact.

This is how a Business Model Mapping looks like

However there is one exception in the form of Lookup Table, which can be left alone but have to enable the Lookup table option

And the each dimension can have only one hierarchy related to it, which means you cannot create two hierarchies from the same dimension table.