A Subflow is a sequence of actions within a Basic, Alternate or Exception Course that is identified with a unique name. A Subflow acts as a building block of Courses. Courses can (if applicable) be build up with Subflows.

For example if we have a set of closely related requirements that form a single goal and help to clarify the requirement more as if we moved them to individual Uses Cases.

All the rules of Basic Courses apply also to Subflows (i.e. they can have Alternate flows, Exception flows etc.)