Sub-Process Start Events

There is only one type of Start Event for Sub-Processes in BPMN: None.

Marker Trigger Description
  None The None Start Event is used for all Sub-Processes, either embedded or called (reusable). Other types of triggers are not used for a Sub-Process, since the flow of the Process (a token) from the parent Process is the trigger of the Sub-Process. If the Sub-Process is called (reusable) and has multiple Start Events, some of the other Start Events MAY have triggers, but these Start Events would not be used in the context of a Sub-Process. When the other Start Events are triggered, they would instantiate top-level Processes.