Event sub-processes are triggered by an event such as a signal or error and require a start and end event. As they are triggered by events an event sub-process can’t be started by a standard start event. Instead start events such as error start events or message start events are used.
Event sub-processes are not connected to the main process flow as they can only be triggered by an event. The XML for an event sub-process contains the triggeredByEvent property set to true.
Event sub-processes can be placed at the process level or inside a sub-process.
When an event sub-process is executed as part of a process instance, it does not receive a new processInstanceId. The elements within the event sub-process will be executed under the ID of the parent process. Process variables are also shared between an event sub-process and its parent with no additional mapping required.