Exception Specification and Handling in Workflow Systems

Various unexpected events frequently happen in workflow system supporting web-based business processes. Thus workflow system should be equipped with handlers to cope with the unexpected events. But in practical terms, we cannot expect for a workflow system to prepare all the handlers for events that might potentially occur. It is more reasonable to let process designers specify exceptional situations and define corresponding exception handlers at process build time. At that time, when exceptional events occur, the workflow system detects the exceptions and invokes corresponding exception handlers. To support this mechanism, a workflow system should provide a means of specifying exceptions and facilities to detect exceptions and invoke corresponding exception handlers. In this paper, we devise an exception specification method using an event-transition approach and its handling mechanism using a design pattern. Detecting exceptions and mechanism for invoking exception-handling routines are developed and incorporated into our research workflow system (ICU/COWS).