Advanced Petri Net Based Flexible Workflow Model Mapping

Workflow model can clearly describe the business processes, and with advances in information technology, the range of its applications is increasingly wide,and the scientific evaluation of workflow model is increasingly becoming necessary. However, traditional workflow management system only execute in accordance with the definition of the workflow strictly , but in practice due to lack of necessary information, lack of resources, business processes change, so unexpected matters, the user needs change the static workflow model to improve the flexibility of the workflow, so that can better adapt to the workflow applications. How to improve the flexibility of workflow has become the one of the most important research topics of workflow management.The flexibility of traditional workflow is low, mainly because the uncertainty of workflow in resources, control, task allocation and other aspacts, separating the modeling from operation, resulting in modeling results can not be applied to the actual situation very well. And there are no tools to systematic analyze and emulate it ,the model can not be evaluated and further optimized. Colored Petri net, which is derived from Petri net, is a set of formal modeling method, with its graphical and mathematical modeling and analysis of tools, supporting concurrency theory, and the network logic and topology as the main content, its simulation and analytical method and tools, it can be used for both static structural analysis and dynamic behavior analysis. Using CPN to map the workflow model for its testing, analysis and optimization is getting more and more attentions of the researchers in this area.In this paper, a series of rules are given which can map the ordinary workflow model into Colored Petri net (CPN) model, which is executable and analyzable in the CPN Tools environment. Some characteristics of the workflow, such as roles, activities, sub-processes, resources and other basic elements are represented with tokens, transitions, substitution transitions, places in the CPN respectively. Some basic structure elements (Sequence, and branches, and connection, or branches, or connections, selection branches) and basic control structures (Sequence structure, parallel structure, single choice, simple merge, cycle, multiple choice, multiple merge)are transformed into CPN models according to the rules given in this paper.In the same time of improveing mapping rules, further improving workflow flexibility. Based on the dynamic structure-based workflow modeling methods, combined with the the characteristics of CPN ,the flexible workflow modeling methods has been improved in this article. This article commenced in the control aspects, on the static modeling aspect dynamic combination methods based on Petri net is proposed, using substitution transition to connect the sub-page with the same input and output interfaces; on the dynamic changes aspect put forward in two implementation methods of flexible workflow chosen method based on Petri nets,one is path selection method based on arc expression and transition guards, proved to improve the dynamic adaptation of workflow execution; the other is user participated selection methods based on "Bind manually",which improves the process operability of workflow.