工作流异常处理的形式描述

异常处理是工作流执行中要解决的主要问题之一，清楚地描述异常处理的过程是最终得到实现的基础。Petri-net对工作流的描述适合于对过程定义进行正确性验证和评价，但描述各种不同条件下的处理策略却很繁琐，采用了一种直观的描述方法对异常处理过程中的元素，即活动、异常处理策略以及处理措施进行了形式化描述，特别是对不同处理策略下的处理过程进行了描述。结合消息机制，分析了一个异常事件出现时，如何处理一个活动实例产生的中间数据，并对事务处理和异常处理的补偿策略进行了比较。描述方法为编码实现提供了很大的方便。

Formal Presentation of Exception Handling in a Workflow System

Exception handling is one of the key issues that computer supported cooperative system must encounter Properly describing the procedure of exception handling is helpful to designing and implementing the funetions in a workflow management system Petri net is a appropriate tool for validating the correctness of process definition and giving evaluation But it is burdensome to describe a variety of procedures under different conditions In this paper, the handling elements including activities, exception events, strategies, and methods are described by means of an intuitional formal presentation, and especially the handling procedures are described under different strategies With message based mechanism, the temporary information produced by the interrupted activity instance is first analyzed and then how to process information by formal presentation is described Finally, the relationship in compensatory operations between exception handling and transaction processing is illustrated The formal presentation of exception handling is the groundwork of coding and implementing exception handling in WfMS