Specification and implementation of exceptions in workflow management systems

Although workflow management systems are most applicable when an organizati on follows standard business processes and routines, any of these processes faces the need for handling exceptions, i.e., asynchronous and anomalous s ituations that fall outside the normal control flow. In this paper we concentrate upon anomalous situations that, although unusu al, are part of the semantics of workflow applications, and should be speci fied and monitored coherently; in most real-life applications, such excepti ons affect a significant fraction of workflow cases. However, very few work flow management systems are integrated with a highly expressive language fo r 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 architectur e of a system, called FAR, that implements Chimera-Exc and integrates it wi th a commercial workflow management system and database server. We discuss the main issues that were solved by our implementation, and report on the p erformance of FAR. We also discuss design criteria for exceptions in light of the formal properties of their execution. Finally, we focus on the porta bility of FAR and on its unbundling to a generic architecture with detached active rules.