Towards Stochastic FMI Co-Simulations: Implementation of an FMU for a Stochastic Activity Networks Simulator

The advantage of co-simulation with respect to traditional single-paradigm simulation lies mainly in the modeling flexibility it affords in composing large models out of submodels, each expressed in the most appropriate formalism. One aspect of this flexibility is the modularity of the co-simulation framework, which allows developers to replace each sub-model with a new version, possibly based on a different formalism or a different simulator, without changing the rest of the co- simulation. This paper reports on the replacement of a sub-model in a co-simulation built on the INTO-CPS framework. Namely, an existing co-simulation of a water tank, available in the INTO-CPS distribution, has been modified by replacing the tank sub-model with a sub-model built as a Stochastic Activity Network simulated on Möbius, a tool used to perform statistical analyses of systems with stochastic behavior. This work discusses aspects of this redesign, including the necessary modifications to the Möbius sub-model. In this still preliminary work, the Stochastic Activity Network features related to stochastic models have not been used, but a simple deterministic model has proved useful in indicating an approach to the integration of Stochastic Activity Networks into a co-simulation framework.