BPMN has an element that looks very much like a subprocess, except drawn with a thick border. Perhaps you have used it yourself... probably incorrectly. Its name is call activity, and it is similar in several ways to a subprocess, but it is not the same. Both elements are important, but valuable for different reasons. This post will explain. Call activity and subprocess share important characteristics. Both are simultaneously a single activity and an activity flow from start event to end event.