| Summary: | 碩士 === 中國文化大學 === 資訊管理研究所 === 90 === Handling workflow exceptions has been widely considered as an important, diffi-cult problem. But most workflow management systems are inflexible in handling ex-ceptions. This thesis considers the problem of handling expected workflow exceptions and proposes an automatic handling model for them. The handling model consists of several major components: the attribute of task, backward point, redo-effect(RE), undo-effect(UE), undo-sequence(US), and cancel-effect(CE).
A workflow typically consists of several tasks, and different task has different importance in a workflow. If a non-vital task fails, workflow execution can continue and make forward progress without any compensation actions. If a vital task fails, workflow execution needs to go back to a previous task with some actions. If a repeatable task fails, it is repeated and re-executed several times until it successes. If a critical task fails, the task cannot be un-done or compensated afterwards.
Often in the context of backward and re-execution it may not be necessary to com-pensate and re-execute all of the steps since they do not produce any new results or the previous results may be sufficient. In such cases, they can result in substantial savings of human and computer resources. Besides, undo and redo are different things. That is, while redo is necessary, undo may not be required, and vice versa.
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