The Modelling And Analysis Of Workflow Based On Petri Net

The Workflow management is one of the studying hotspots in the Information Era, and has been applied in many fields. The workflow model is the significant content in the workflow technology. The verification and performance evaluation of the model is the principal theoretical basis and supporting technique of the studies and applications of the workflow system. With the advantages of formal semantic definition, visually graphical expression, firm mathematical foundation and description based on state, the Petri net is applied to model and optimize the workflow process more and more. This paper describes the process of workflow based on Petri net theories, introduces a kind of workflow model梬orkflow net, analyzes the structural correctness (soundness) of the workflow net using the structural analysis method, such as incidence matrix, state equation, P/T-invariant, and deduces a necessary condition for soundness. Furthermore it discusses two kinds of workflow nets, which are state-machine and marked-graph, and draws a conclusion that all SMWF and non-cyclic MGWF are sound. For the large-scale and complex systems, it sets up hierarchical workflow net based on the theory of refinement, then puts forward the conditions how to satisfy the soundness, state invariability and behavior invariability for the compositional net. For the performance evaluation, it analyzes the performance of the workflow quantitatively, such as mean service time and resource utilization rate, based on Generalized Stochastic Peri net theories, particularly the performance equivalence formulas of the four basic constructs (sequential, parallel, conditional and iterative) are deduced; in the end taking an application case as an example it explains the method and steps of hierarchical analysis.