When an instance arrives to a Process Creation activity, the Process Execution Engine creates an instance in the subprocess associated to the Process Creation activity. If there is no Termination Wait activity associated with the Process Creation activity, the Engine runs the subprocess and the rest of the process flow simultaneously.
If there is a Termination Wait associated to the Process Creation activity, the Engine runs the subprocess and the flow objects that may exist, simultaneously. The instance flows to the next activity when the Engine finishes running the flow objects previous to the Termination Wait. When the instance in the subprocess arrives to the End, the subprocess notifies the associated Termination Wait. Then the Engine maps the output arguments of the subprocess to the process instance variables, using the defined argument mapping.
If the instance in the parent process arrives to the Termination Wait before the Engine finishes running the subprocess, and the property Process Notification Immediately is selected, then the Engine processes the notification and the argument mapping in the same transaction.