Extending the Four-Variable Model for Cyber-Physical Systems

As Cyber-physical System (CPS) is gaining more and more concerns recently, the requirements modeling becomes a critical issue in CPS. In this paper we propose a requirements model for CPS by extending the Four-Variable Model. Through extension, the requirements model deals with complex network environment that CPS are facing, and views timing and position requirements as functional requirements. Besides the framework of this model, we also give a guiding process on how to select corresponding environment variables in this model. An example on one-way traffic light is illustrated to show the effectiveness of our approach.