Modular Modelling of Large-Scale Systems using Communicating X-Machines

Abstract. A X-machine is a general computational machine that can model non-trivial data structures as a typed memory tuple as well as the dynamic part of a system by em-ploying transitions labeled with functions that operate on inputs and memory values. The X-machine formal method is rather intuitive, while at the same time formal de-scriptions of data types and functions can be written in any known mathematical nota-tion. A set of X-machines can be viewed as components, which communicate with each other. This paper describes a methodology of building communicating X-machines from existing stand-alone X-machine models. It is suggested that the development of complex systems can be split into two separate activities: (a) the modeling of stand-alone X-machine components and (b) the description of the communication between these components. The approach is disciplined, practical, modular and general in the sense that it subsumes the existing methodologies. The proposed methodology is ac-companied by an example, which demonstrates the use of communicating X-machines towards the modeling of large-scale systems.