Study On Adaptive Workflow Model And Implementation Mechanism

With the development of workflow technology and its deep practice application,workflow system is required more for its function. The research and realization aboutadaptive workflow is an important problem. In order to enhance the adaptability,adaptive workflow system should have strong ability of exception handling anddynamic change, and the ability of transaction processing, which can improve thecorrectness, data consistency and muscularity of workflow system.The adaptive workflow modeling, implement methods and the theory ofexception handling and dynamic change are researched in this dissertation, thetransaction processing in the adaptive workflow is also discussed. The material workis followed:(1) Research on the definition and implement methods of adaptive workflowmodel.Active rule is named ECA(Event-Condition-Action) rule, it has strong ability ofsemantic expression. When event occurs, the system will check the condition of ruleat real time or at the prescribe time. If the condition is correct, the action will beexecuted. Workflow model is a process represent, it describes the process oftransaction handling, the process includes some material activities. So workflowtransaction handling process and the dependent relationship among activities can bedescribed by ECA rules. Adaptive workflow system has uncertain processes, therelationship among processes is not invariable. To pledge the adaptive capacity, thecorrectness and consistency, the describe language for workflow model should depictthe changed model and hand over the executed instance to the news model forexecuting. In this paper the adaptive workflow model definition language is based onXML(Extensible Markup Language)and XML Schema, which can descript adaptiveworkflow model sententiously and truly. The dynamic characteristic of the adaptive workflow includes two aspects: timeand workflow process constitutes. For the time aspect, a workflow system includesestablishment phase and running phase. These two phases affect one another. Forprocess constitutes aspect, the dynamic characteristic of adaptive workflow includes:process definition can define the dynamic behavior and the expression of theincertitude processes and activities. When an activity is run, the workflow can changethe pre-defined flow or uncertain dynamic thing. The XML parser can easily parse the documents of adaptive workflow which isdepicted by XML and XML Schema. This language depicts a series of adaptiveworkflow model entities. Each entity begins with relevant beginning key words, thenmark symbol, property table and end key words. At the running period of adaptive workflow, the processes and activities areexecuted in order by the ECA rules which depict the relationship among processes,activities, processes and activities. Rule manager detection and controls, explains,manages and preserves the ECA rule set. Event manager detects the trigger event,explains and detects the current executive trigger condition and executes the relevantaction process. The execution control of adaptive workflow model includes event manager,communication manager, rule execution control unit and rule manager.communication manager realizes the communication between control unit and theworkflow management system. Event manager accepts and handles the internalmessages from the workflow management system and other units, creates eventqueue in term of sequence. Rule control unit executes rules, it attempers resource andassigns tasks. Rule manager manages, detects and control, vindicates rules. (2)Transaction handling in adaptive workflow Workflow is a set of a series of ordinal operation, but these operation are not justthe data of database. Workflow also has transaction character. The transaction inadaptive workflow system has structure executive dependency. When the transactionis failure, the system will using compensate task, failure task and reverse-doing taskto realize the workflow resume for solving the disagreement problem brought byworkflow failure. (3)Exception Handling in adaptive workflow In workflow management system, when the executive environment is changed,the execution of some processes and activities will generate deviant realizations.Workflow system exists all kinds of anticipatory, un-anticipatory, wrong things whenit executes processes. These things are exception. Exception handling includes thefollow associated aspects: exception detection (detect the workflow system exceptionstatus), exception analysis and position, exception expression and resume. Theexception handling objects are anticipatory and un-anticipatory exception. The mainobjects are executed-failure activity, executed-refusal activity, executed-delayactivity and semantic-exception activity. The exception detection handling model includes three parts: exception detectionand analysis, exception case base(ECA rule base), flow change. The key of detectingexception is how to judge what kind of exception status occurs, the position ofexception happened point and saving the normal system status before the exceptionoccurs. Since exception has two types: anticipatory and un-anticipatory exception,exception detection has two types too: anticipatory exception detection and un-anticipatory exception detection. Calling exception handling process has two types:by message and by activity status. By the way, exception handling are not all direct,sometime exception handling is transferred. (4)Theory and implement of Dynamic change in adaptive workflow In fact, workflow system can't confirm all the processes, and the relationshipamong processes is not invariable. To confirm the adaptive characteristic, the systemmust has the ability of dynamic change. Dynamic change operating set includes five type of model elements: workflowprocess activity, transfer information, global data, local data, defined data(data typeis defined by user). For these model elements, three change operation are allowed:add model element, modify attribution information, delete model element.