13.3.4 Sub-Process/Call Activity

A Sub-Process is an Activity that encapsulates a Process that is in turn modeled by Activities, Gateways, Events, and Sequence Flows. Once a Sub-Process is instantiated, its elements behave as in a normal Process. The instantiation and completion of a Sub-Process is defined as follows:

A Sub-Process is instantiated when it is reached by a Sequence Flow token. The Sub-Process has either a unique empty Start Event, which gets a token upon instantiation, or it has no Start Event but Activities and

Gateways without incoming Sequence Flows. In the latter case all such Activities and Gateways get a token. A Sub-Process MUST not have any non-empty Start Events.