Modeling complex process systems with subject-oriented means

In an organization more or less all business processes are interconnected forming a large network or ecosystem of related activities. To describe (model) such complex process systems a formal language must offer the possibility to structure the according models. It must allow to describe the environment of a considered process and illustrates its relationships to other process models. Furthermore, it should not require that all connected models are created at the same time by the same persons with the same knowledge about all other process models and their constraints. In this article we describe a method to model business process model systems with an arbitrary number of abstraction levels. We introduce the structuring concept in the subject-oriented language PASS and show how the concept can be also applied in BPMN models. Furthermore, we present a fundamental discussion and disagreement about extends and choice of vocabulary that is derived from this concept.