An elementary Petri net based model for distributed system design

In this paper we discuss an elementary net (EN) based model in which there are 3 levels named L/sub 1/, L/sub 2/, L/sub 3/ respectively. In the level L/sub 1/ on an EN the arcs, events and places can be interpreted in order to use it easily in system design. In L/sub 2/, it is also a graphic model, each node has their own implementation by EN. More precisely there are two kinds of function nodes and two interface nodes in it. The function nodes have 'parallel', 'choice', 'send', and 'receive' for the nodes of interface. Using L/sub 2/ a three processors cooperative computing system is introduced to demonstrate the advantages of L/sub 2/. Considering the design complexity, a very high level model L/sub 3/ which is a model more higher than L/sub 2/, is established, in which there are three useful macros called 'synchronization', 'decision' and 'guarded'. Modelling a two processors system by L/sub 3/ makes the model to have more sense.