工作流分层模型的PNML表示

PNML是一种基于XML的Petri网交换格式，在工作流引擎内部使用PNML表示业务流程的模型，可以使得引擎和其他支持PNML表示的工具之间具有很强的互操作性．为此需要先定义新的标签，然后给出新的Petri网类型定义，最后通过例子阐明了如何用扩展后的PNML表示工作流分层模型．借助PNML表示，实现的工作流引擎工具具有很强的扩展性，能够和其他支持PNML的工具进行数据交换．

PNML Representation for Layered Model of Workflow

The PNML is an interchange format, which can be extent to represent all kinds of Petri net. Many institutions have done much research about the extension of PNML. In order to represent the model of business process inside workflow engine, PNML is used in the layered workflow model. The layered workflow model used in workflow engine has three levels: WL-net on logic level is a constraint of P/T-net, WS-net on semantic level is a new kind of Petri net, namely, C-net. While the models, namely, WM-logic and WM-Semantics on the management level are the dual systems to the WL-net and WS-net, respectively. To represent this layered model using PNML, we need to extend the original markup language with new Labels to define new types of Petri nets, namely, C-net. This paper describes the extension to label transitions, arcs and places using some tables. The representation based on PNML can express the layered model exactly. In the end this article presents an example to show how to represent model of workflow with PNML. With the help of PNML representation, the workflow engine could easily adapt to various tools supporting PNML, and smoothly exchange their data.