What is Co-Model

The pace of innovation in Cyber-Physical Systems (CPSs) drives the need for multi-disciplinary methods and tools to support rapid and accurate assessment of design alternatives. In this chapter, the authors describe collaborative models (co-models) that link Discrete-Event (DE) models of control software with Continuous-Time (CT) models of controlled plant. They present methods and tools for co-modeling using VDM as the DE formalism, and bond graphs on the CT side, using the Crescendo platform to link existing simulators (Overture for VDM and 20-sim for bond graphs). The authors discuss the exploitation of co-models within the design flow, including their use with SysML, and the roles of Software-in the-Loop and Hardware-in-the-Loop simulation on the way to realising co-models in cyber and physical media. The authors identify research challenges in providing sufficient model fidelity and the evidence needed to support the engineering of certifiably dependable systems.