Improving Backward Recovery in Workflow Systems

The notion of compensation is widely used as means of backward recovery in long-lived transactions as well as business processes supported by workflow management systems. In general, it is non-trivial to design compensating tasks for tasks in the context of a workflow. Actually, a task does not have to be compensatable. In this paper, we first look into the requirements that a compensating task has to satisfy. Then we introduce a new mechanism called confirmation. With the help of confirmation, we can modify some non-compensatable tasks so that they become compensatable. This greatly improves backward recovery for workflow applications in case of failures. To effectively incorporate confirmation and compensation into the workflow management environment, a three level bottom-up workflow design method is introduced. The implementation issues of this design are also discussed.