Exception handling using task deferral in document-driven workflow systems

This paper analyzes various causes of exceptions at the task level in a workflow system. Conventional control flow based workflow systems mix hard constraints like data dependencies between tasks with soft constraints like business rules. Thus, they lack flexibility and are not suitable for ad hoc workflow applications where exceptions arise frequently. We first show that document-driven workflow systems are more suitable for such environments. Second, we propose an exception handling mechanism based on task deferral in document-driven workflow systems and give an algorithm for implementing it. Our work is particularly relevant for real-time workflows with deadlines.