Research on engineering processes plays a major role within engineering design research, since ``the bulk of the effort involved in product development lies in perfecting the underlying processes'' (Panchal et al. 2004). Processes are getting even more important when considering the emerging research topic of product service systems (PSS): PSS are an integration of product and service elements in one market offer (Baines et al. 2007). Thereby not only design processes have to be considered but also the service product itself may be modeled as a process (Bullinger et al. 2003).