Research On An Exception Handling Model In Workflow

The popularization of the Internet/Intranet applications and the development of Web technology provide a perfect foundation for the realization of the Web-Based workflow management systems, and then the services of the Web-Based workflow management become the perfect base of the collaboration between enterprises which not being in same place. It has been primary characteristic of new-style workflow management system that the Web technology is adopted. Demanded to work normally in general status, the system furthermore must have capability in handling all kinds of exceptions flexibly. The data must maintain consistent by some methods when exception raised. Means and ways must be taken to guarantee the system working in order although some failures occurred at the node of workflow. The unexpected exceptions should be altered to a expected exception so that to be handled conveniently for the workflow's finishing in normal ways although with exceptions.In this paper, an exception handling model was proposed after had analyzed deeply the exceptions that likely occur within the context of workflow systems. This model expanded the standard workflow management system reference model to include exceptions handler which made up of rule Base, exception handling database, discovery module and rule searching module. The data structure of exception handling rule was discussed deeply and the concept of hierarchy structure was introduced to describe the attributes of the rule and an exception handling rule base whose data formed in hierarchy structure was designed to save the exception handling rules. When exception rose, the workflow monitor could get helpful reference from the exception handling rule base via exception handling mechanism searching from this base. For finding the most similar exception handling rule from exception rule base, the searching algorithm with low time complexity was designed. The algorithm adding new handling rule into exception handing base and filtering old rule to discard in rule base was designed. The exception handling mechanism was realized in a practical workflow management system. The exception database, the API of searching rule, the API of adding rule and the API of filtering rule was designed in this workflow management system. Then a workflow instance was cited to validate the feasibility of the mechanism.