Ad-hoc recovery in workflow systems : formal model and a prototype system

Xing, Xuemin (1999) Ad-hoc recovery in workflow systems : formal model and a prototype system. Masters thesis, Memorial University of Newfoundland.

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Abstract

A workflow management system (WFMS) facilitates business processing (workflow) across distributed nodes. State-of-the-art WFMSs do not have adequate support for the dynamic changes during the workflow execution. This thesis focuses on one of the dynamic problems, ad-hoc recovery. It is a phenomenon that occurs in workflow applications when an agent needs to alter the control flow prescribed in the original definition. Specifically, we are interested in the backward ad-hoc recoveries, in which the control flow is redirected backward. When this happens, some tasks will be re-executed and consistency problems may arise. In our proposed ad-hoc recovery model, the key components of the ad-hoc recovery are defined and some constraints are given to ensure the correctness of the workflow execution. We also present a WFMS prototype, describing its design strategy and implementation method, as well as a related protocol, as one application of this model. The protocol is exemplified by a hospital workflow. Some performance issues are also discussed.

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