The Design And Implementation Of Expected Exception Handling In Workflow System

With the formation and the development of global economy and international market, the environments of business become more and more dynamic and uncertain. In order to make for further progress and adapt to the drastic competition, enterprises are forced to seek for a more reliable framework that could not only react to the changes of business environments promptly and quickly, implement effective and real schema, but also harmonize and optimize business processes wholly. Workflow technology is nowadays an essential technique to integrate distributed and heterogeneous applications and information systems as well as to improve the effectiveness of business processes. Workflow is automation of a business process, and a Workflow Management System(WFMS) assists in defining, implementation and managing the execution of a workflow. A WFMS generally provide functions in both buildtime and runtime environments, where the buildtime environment provides design tools to specify processes and the runtime environment services for process automation and monitoring.Deviations from workflow processes that achieve the process goals completely and with maximum efficiency are unavoidable, which can be considered as exceptions. Exceptions may arise from erroneous process definition, shortage of resources, communication failures, changes in organizational structure. A WFMS needs exception handling mechanism to deal with those deviations to support adaptive features. It is crucial to allow the system to continue processing even if exceptions occur. Current workflow systems are ill-suited to support dealing with exceptions occurred during runtime correctly and reliably. Most of those carry out exception handling through including conditional branches to deal with anticipated exceptions where happenchances may occur and that is short of enough flexibility. Current process modeling methodologies and tools do not, however, make any provision for describing exception handling procedures separately from "main-line" processing. Inclusion of exception handling branches, therefore, can greatly complicate process models and make the process more difficult to be defined, understood, and modified. Current workflow modeling methods provide, in addition, no support for uncovering what kinds of exceptions can occur in a given process model, and how they can be resolved. Although it has obtained plentiful and substantial achievements in the development of the workflow technology, it will also remain to be further perfected on the aspects of how to improve the capability of faulty tolerance and adaptability of the system. Exception handling in workflow is one of the most keys in the design of the workflow system and the enaction control of the workflow processes.1.The main content of this thesisThrough analyzing the problems of exception in workflow systems and the requirements of the functionality of exception handling, aimming at complexity and initiative of exception handling, this thesis puts forward a rather flexible framework in which the problem of workflow expected exception handling can be adequately addressed. This thesis presents a solution for implementing more reliable processes by using exception handling and it contributes a great deal to improve the capability of faulty tolerance and adaptability of the system. The thesis firstly introduces an exception centric model of the workflow system, describes in deatil all the aspects on definition, triggering, monitoring and handlers of workflow exceptions. It implements the separation of the workflow excpetion handling logic from "main-line" processing.Secondly, the thesis designs and implements the most function of the core architecture of the framework. The exception manager is responsible for controlling exception handling. The exception manager could offer more perfect expected exception handling mechanism with the help of the enactment monitor , the recovery manager and the human dealer , and such method could support dealing unexpected exception effectively. Moreove...