پردازش وب رابط محور به استثنا شرکت تعاونی در ADOME سیستم مدیریت جریان کار

Exception handling in workflow management systems (WFMSs) is a very important problem since it is not possible to specify all possible outcomes and alternatives. Effective reuse of existing exception handlers can greatly help in dealing with workflow exceptions. On the other hand, cooperative support for user-driven computer supported resolution of unexpected exceptions and workflow evolution at run-time is vital for an adaptive WFMS. We have been developing ADOME-WFMS as a comprehensive framework in which the problem of workflow exception handling can be adequately addressed. In this article, we present an adaptive exception manager and its web-based interface for ADOME-WFMS with procedures for supporting the following: reuse of exception handlers, thorough and automated resolution of expected exceptions, effective management of Problem Solving Agents, cooperative exception handling, user-driven computer supported resolution of unexpected exceptions, and workflow evolution.

Workflow management system technology, though recent, has been regarded as one of the main types of advanced information systems. It is perceived that workflow technology not only requires the support for complex data model functionality, but also flexibility for dynamically modifying the workflow specifications, especially in cases of exception handling. Because of unanticipated possibilities, special cases, and/or changes in requirement and operation environment, exceptions may occur frequently during the execution of a business process. An exception is an event (i.e., something that happens) that deviates from normal behavior or may prevent forward progress of a workflow. Upon unexpected exceptions, a comprehensive WFMS should be able to support the users to reallocate resources (data / object update) or to amend the workflow, such as adding alternatives (workflow evolution). Further, frequent occurrences of similar exceptions have to be incorporated into workflow specifications as expected exceptions. Such workflow evolution can help avoid unnecessary exceptions by eliminating error-prone activities, adding alternatives, or by enhancing the operation environment. This can lead to a WFMS that supports workflow adaptation through exceptions. In contrast with traditional software systems, workflows usually evolve more frequently, making reuse a vital issue. Reuse of workflow definitions and exception handlers are very important for the smooth operation of a flexible WFMS. Support for workflow evolution at run-time is vital for an adaptive WFMS. There have been a few WFMSs designed to address these two problems (viz. reuse issues and workflow evolution) effectively and adequately. However, none of them is based on a me&modeling exception-centric approach. With a meta-modeling approach, we can have a simple but expressive core data dictionary (metaschema). From this me&level schema, users can define all other classes for the WFMS, including activity schemas, exceptions and handlers. Further, from these schemas WFMS objects (in particular, activity instances) can be instantiated. This contributes a substantial improvement to WFMS modeling based on relational models because the entity modeling and implementation is tied together in a straightforward manner. Extensive reuse can also be facilitated as discussed in Section 5. We use an integrated, event-driven approach for execution, coordination, and exception handling in our WFMS. Events (such as database events I exceptions, or external inputs) trigger the WFMS ExecutionManager to start an activity. The WFMS Execution Manager uses events to trigger execution of tasks, while finished tasks will inform the Execution Manager with events. A task is executed by a problem solving agent (PSA) which is a hardware/software system or a human being. Upon an exception, exception events will trigger the WFMS Exception Manager to take control of resolutions. These resolutions can trigger a software solution or will involve a human to cooperatively resolve an exception. An effective user interface is vital to the execution of the above features. We choose to use a webbased user interface because workflow and agents tends to be widely distributed, even involving other organizations across the Internet. Mobile clients can be supported (alerted by ICQ or electronic mail) by the Internet, and they can access the WFMS with a web-browser. Direct message passing between clients and remote data sharing can be facilitated. On the other hand, web-based tools are a prevailing technology that has a wide range of utilities and off-the-shelf applications, supporting wide ranges of hardware and software platforms at a relatively low-cost. In this regard, we have developed ADOME-WFMS, based-on an Advanced Object Modeling Environment (ADOME [45]), with a novel exception centric approach. The key features are as follows: 1. Effective coordination of PSAs and an object-oriented capability-based approach to match tasks and agents; 2. Automatic resolution of expected exceptions and exception driven workflow recovery; 3. Dynamic binding of exception handlers to activities with scoping, and to classes, objects and roles; 4. Addition, deletion and modification of exception handlers at run-time through workflow evolution; 5. Specifying and reusing exception handlers upon unexpected exceptions and system-assisted exception handling; and 6. Application of workflow evolution and workflow recovery in exception handling. Thus, adding a web-based user interface allows ADOME-WFMS to effectively support distribution of PSA and workflow execution even with a centralized control design. In this article, we present a framework for flexible workflow enactment and online workflow evolution in an advanced object environment (active OODBMS with role and dynamic schema support), with reference to ADOMEWFMS. More details regarding classification of exceptions and handlers, and modeling aspects for ADOME-WFMS are given in [22]. In addition, ADOME-WFMS exception driven workflow recovery has been presented in [26]. The objectives and contribution of this article include: (i) the mechanism of ADOME-WFMS and resolution of expected exceptions, (ii) support of reuse for workflow definitions, constraints, exception types and handlers in ADOME-WFMS, (iii) an augmented solution for exception handling based on workflow evolution, (iv) management of distributed PSA and allow for distributed users, (v) user-driven computer supported resolution of unexpected exceptions, and (vi) demonstrating the use of ADOME-WFMS in supporting exception handling through effective web interface facilities. The rest of our article is organized as follows. Section 2 presents a me&modeling approach to activity modeling, which facilitates reuse and workflow evolution. Section 3 presents the architecture of ADOME-WFMS with web-based PSA coordination and general mechanisms. Section 4 discusses how ADOME-WFMS resolves for expected exceptions. Section 5 explains how reuse can be facilitated. The ADOME-WFMS Human Intervention Manager is detailed in Section 6 to illustrate how unexpected exceptions are handled in ADOME-WFMS, with novel web-based workflow evolution functions. Section 7 compares related work. Finally, we conclude the article with our plans for further research in Section 8.

This article has presented adaptive exception handling in ADOME-WFMS, a flexible WFMS based on an active OODBMS extended with role and rule facilities (viz., ADOME). Compared with other research on this topic, ADOME provides an advanced object-oriented environment for developing a WFMS, which can adapt to changing requirements, with extensive support for reuse. In particular, the resultant system (i.e., ADOME-WFMS) supports a rich taxonomy of exception types and their handling approaches, and a novel augmented solution for exception handling based on workflow evolution. Effective reuse of workflow definitions, exceptions, handlers and constraints in ADOME-WFMS are also possible. This article has also described in detail, how expected exceptions are actually resolved with the ADOME-WFMS Exception Manager and how unexpected exceptions are handled through its Web hzterjice. It should be noted that, though exception handling is highly automated in ADOME-WFMS by scoping, binding and reuse, human intervention management must be provided to support for (totally) unexpected exceptions and drastic workflow evolutions. Moreover, the Web Interface also demonstrates effective management of human PSAs, especially during exceptions. ADOME-WFMS is currently being built on top of the ADOME prototype system, with a web-based user interface to accommodate the whole range of activities. We are also porting the ADOME-WFMS Activity Editor to a web-based version to support web-based workflow evolution with full graphics capability. On the theoretical side, we are looking at reuse models in a more formal way, and the possibility of applying UML technologies to this aspect. We are also interested in performance evaluation and optimization of workflow exception handling [39]. Further research issues on interfacing and interoperability are emphasized for extending the applicability of an advanced WFMS engine, which includes: expanding the possible interfaces and coordinating different types of agents, graphical workflow evolution tools, and inter-operating with other WFMS. We are in the process of developing E-ADOME [22], an extension of ADOME-WFMS with coordination mechanisms for different kinds of agents, in various advanced real-life e-commerce environments, such as procurement, finance, stock-trading and insurance. We are especially interested in the RosettaNet Internet business communications standards (a framework using XML to streamline the computer product and IT supply chain). Finally, it should be noted that exceptional handling, and especially unexpected exception handling is a very tough problem which requires an in depth application domain knowledge to build a usable solution. The solutions elaborated in this paper can be fine-tuned for a specific application domain or area (as illustrated in [22]) so that such usable and practical systems can be built. In this regard, this paper describes in detail such a pragmatic solution to the exception-handling problem in workflow management systems.