Modes, features, and state-based modeling for clarity and flexibility

The behavior of a complex system is frequently defined in terms of operational modes-mutually exclusive sets of the system behaviors. Within the operational modes, collections of features define the behavior of the system. Lucent and understandable modeling of operational modes and features using common state-based notations such as Statecharts or Stateflow can be challenging. In this paper we share some of our experiences from modeling modes and features in the medical device domain. We discuss the challenges and present a generic approach to structuring the modes and features of a generic Patient-Controlled Analgesia infusion pump.