A workflow management systems architecture that support ad-hoc recoveries

Ad-hoc recovery is a phenomenon that occurs in workflow applications when an agent needs to alter the control flow prescribed in the original definition. It is usually caused by unpredictable reasons, such as an unexpected output of some individual tasks, events or exceptions due to the changing environment, etc. Due to its irregularity in nature, ad-hoc recovery in general cannot be dealt with by using a pre-defined exception handler. On the other hand, since it allows changes without following a particular pattern, it offers greater flexibility than many existing workflow products do. In this paper, we introduce the concepts relating to ad-hoc recovery, and suggests approaches to supporting this phenomenon in practical applications. We concentrate on the architectural aspects at the workflow management system level, and describe functionalities of the main components and their interactions.