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Open Access Publications from the University of California

A model of processes based on petri nets

  • Author(s): Gostelow, Kim P.
  • Van Weert, Tom J.
  • et al.

This paper describes the Set Model of processes which was developed to help put the design of process-oriented systems on a sound footing. The basis of the Set Model is that of a process description: any sub-net of a Petri net, such that, the sub-net is itself a Petri net. The real strength of the definition appears when one realizes that Petri nets and Petri sub-nets are defined as sets. Thus, process descriptions are related just as their set descriptions are related (for example, sharing is set intersection), and set theory is used to operate on process descriptions. The definition may be applied recursively, in that the Petri net processor (the process which interprets nets in Petri net language by firing transitions and moving tokens) of a given Petri net may itself be described by a Petri net. Thus the Set Model can represent micro-programmed machines and multi-level interpreters. As an example, the model is used to describe a procedure whereby any number of producer and/or consumer processes can construct a channel for interprocess communication. The technique allows parallel and independently operating channels to be constructed. In contrast to other models of processes and their communication, interprocess communication is not a postulated component of the model, but rather is constructed from more basic notions. Also the Set Model shows how Petri nets can be used to model the dynamics of systems, such as the creation and destruction of processes and intermodule linkage.

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