An iconic approach to parallel design

The objective of this paper is to determine whether a method can be devised to overcome several problems inherent to the design of processes which execute in parallel. Specifically, what is required is a technique which: 1) can display objects in parallel, 2) can hide unwanted detail, 3) can expose timing and communication, and 4) can translate the graphic model into code. Petri net theory is used as the basis for the graphic model while Occam is used as the target language. The hardware model onto which the model is mapped is a system of Transputers. The concept of creating icons for the primitives and constructs is used to develop the building blocks for more complex design. Icons for all Occam primitives, special processes, and constructs are created. The Occam process provides the basic model for a macro which can be used to hide detail. This is used to create a model for fault tolerant design which can be included in a model. A communications package is selected from the routines needed for a distributed operating system as an example to model with the iconic technique. The hardware configuration for the system is presented to provide further basis for design. The routines are developed and then combined into a system which represents a trivial application using one communication link between two transputers. The reachability tree, part of Petri net theory, is used to analyse the system. The modelling technique is successful as far as it has been developed and the approach appears to be sound. It holds the promise of greater effectiveness if development continues. The implementation of the technique in software would add to its value significantly