Functional decomposition and major business control diagram

On the top-level BCD, which includes all major functions, you can drill down on the function level. To view the functional decomposition, double-click Function, which is located directly beneath each major function. The Function command provides a full overview of all main functions that belong to the major function.

Cases are made out of the same main functions, which are shown in the functional decomposition.

The difference between a case and a functional decomposition is that cases only represent the main functions that are used in the case. This implies that some of the main functions are only shown through the functional decomposition, since they are not used in a case.

Therefore, you must check the functional decomposition during implementation to ensure that no functions are missed that must remain as a part of the model.