Specification and Implementation of Exceptions in Workflow Management Systems

Although workflow management systems are most applicable when an organization follows standard business processes and routines, any of these processes faces the need for handling exceptions, i.e., asynchronous and anomalous situations that fall outside the normal control flow. In this paper we concentrate upon anomalous situations that, although unusual, are part of the semantics of workflow applications, and should be specified and monitored coherently; in most real-life applications, such exceptions affect a significant fraction of workflow cases. However, very few workflow management systems are integrated with a highly expressive language for specifying this kind of exception and with a system component capable of handling it. We present Chimera-Exc, a language for the specification of exceptions for workflows based on detached active rules, and then describe the architecture of a system, called FAR, that implements Chimera-Exc and integrates it with a commercial workflow management system and database server. We discuss the main issues that were solved by our implementation, and report on the performance of FAR. We also discuss design criteria for exceptions in light of the formal properties of their execution. Finally, we focus on the portability of FAR and on its unbundling to a generic architecture with detached active rules.