Simulation models at the development of distributed data processing systems

The development of control systems often implies the necessity of the organization of parallel computing processes or the implementation of software of distributed data processing. Solving these problems we should carry out such stages as constructing the system structure, developing the scheme of process communication and choosing special language tools of parallel programming. Formal tools of simulation such as Petri nets and their extensions can lighten the resolution of these problems. The communication of parallel processes is described by the net structure, which can be easily obtained from the process state graph and the algorithm implemented by this process. It is important to note that Petri nets allow to describe asynchronous and parallel independent events. Occurrences of transitions act as events and result in creating, moving and deleting tokens. In this case the processes are represented by tokens, and the cortege of token attributes acts as a data segment of the process. To this effect the object-oriented modification of the hierarchical E-nets is developed.