Visual formalisms are very popular in specification and design of software and hardware systems, especially in workflow systems. Visual languages have the advantage of being simple to use for system designers. In this paper, we introduce a new modeling framework based on the Calculus of Communicating Systems (CCS), to describe behaviours between processes in intricate workflows. The framework of our method is both visual and formal. In addition, we abstract a hierarchical structure of workflow specification, which allows changes in workflow structure without modifying the programs that implement the workflow tasks.
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