Complexity Challenges in Cyber Physical Systems

5A Unifying Framework for the Hierarchical Co‐Simulation of Cyber‐Physical Systems

Fernando J. Barros

Department of Informatics Engineering, University of Coimbra, Coimbra, Portugal

5.1 Introduction

The representation of complex cyber‐physical systems usually requires the combination of models expressed in different formalisms/paradigms. The interoperability of heterogeneous models becomes a major requirement for the simulation of complex systems. In this section, we propose the Hybrid Flow System Specification Formalism (HYFLOW) as a unifying framework for M&S of hybrid systems.

The advantages of a unifying formalism include the homogeneous treatment of all types of models. A unifying formalism makes all models interoperable by design, requiring no special glue operators traditionally necessary to combine heterogeneous models (Praehofer 1991). Unifying formalisms have been created in other areas, like physics, where, for example, the work of Newton provides the foundations of classical mechanics.

HYFLOW provides a description of modular hybrid models that combine sampling (Barros 2002) with discrete events (Zeigler 1984). HYFLOW models can be independently simulated since their interaction is exclusively based on message passing that guarantees model encapsulation since this type of communication requires no access to model state. Formalism co‐simulation is supported by two basic operators: the ability to exactly represent dense outputs on a digital computer and the concept ...