The purpose of the Functional Decomposition diagram is to show on a single page the capabilities of an organization that are relevant to the consideration of an architecture. By examining the capabilities of an organization from a functional perspective, it is possible to quickly develop models of what the organization does without being dragged into extended debate on how the organization does it.

Once a basic Functional Decomposition diagram has been developed, it becomes possible to layer heat-maps on top of this diagram to show scope and decisions. For example, the capabilities to be implemented in different phases of a change program.