An object of the Call activity type is included in the transformation to XPDL only if it references a global process of the BPMN collaboration diagram (BPMN 2.0) type having at least one start event of the None type. The control flow is transferred to the invoked process. In this case, the referenced process is added to the XPDL file as an additional empty element of the WorkflowProcess type. This element is referenced in the Activity element that represents the object of the Call activity type in the SubFlow element.
If an object of the Call activity type does not reference any global process it is handled like a normal task.