The sub-process element is used to enhance process readability by logically grouping certain steps and present the user with high level steps. The element contains other activities, gateways, events, and so on which form a process that is part of another process. It enables you to collapse the process steps and treat them as a single element.

A Sub-Process can only be used inside a parent process. It cannot be invoked by another process by using a Call Activity. A process that is defined in a Sub-Process element is not reusable, that is, other processes cannot call this process through the Call Activity element.

The following illustration shows an example of embedded sub-process workflow.