Exception Handling in Workflow Systems

Service-oriented software systems are inherently complex and have to cope with an increasing number of exceptional conditions in order to meet the system’s dynamic requirements. This work proposes an architecture framework which has exception handling capability. This framework ensures the credibility of service-oriented software, during the architectural stage, by adding exception handling-related architecture elements and modeling exception handling process. It allows a clear separation of concerns between the business function and the exception handling unit, using reflection mechanism. It plays an important guiding role for achieving reliable service-oriented system.

In the RF system for FLASH (free electron laser in Hamburg) linear accelerator each klystron supplies RF power to up to 32 cavities. The superconducting cavities are operated in pulsed mode and high accelerating gradients close to the performance limit. The RF control of the cavity fields to the level of 10 for amplitude and 0.1 degree for phase however presents a significant technical challenge due to the narrow bandwidth of the cavities which results in high sensitivity to perturbations of the resonance frequency by mechanical vibrations (microphonics) and Lorenz force detuning FLASH linac RF control system employs a completely digital feedback system to provide flexibility in the control algorithms, precise calibration of the accelerating field vector-sum, and extensive diagnostics and exception handling capabilities. The RF control algorithm is implemented in DSP (digital signal processor) firmware and DOOCS (distributed object oriented control system) servers. The RF control system design objectives are discussed Hardware and software design of the DSP based RF control are presented.

This paper presents a pair of role-based access control models for workflow systems, collectively known as the W-RBAC models. The first of these models, W0-RBAC is based on a framework that couples a powerful RBAC-based permission service and a workflow component with clear separation of concerns for ease of administration of authorizations. The permission service is the focus of the work, providing an expressive logic-based language for the selection of users authorized to perform workflow tasks, with preference ranking. W1-RBAC extends the basic model by incorporating exception handling capabilities through controlled and systematic overriding of constraints.

Business process execution language for Web services (BPEL4WS) has been proposed for composing Web services into a new one. A BPEL4WS description requires the specification of both the normal flow and the possible variations due to exceptional situations that can be anticipate and monitored. Nevertheless, defining exception handling is often in ad hoc way, it is up to the service developers to define how to deal with these exceptions. This paper uses policy to capture the common part of exception handling and presents a multi-policy exception handling system (MPEHS) to provide system level solution. These policy can be reused in different BPEL processes and simplify the work of BPEL process developer.

Workflow management systems (WfMSs) are being increasingly deployed to deliver e-business transactions across organizational boundaries. To ensure a high service quality in such transactions, exception-handling schemes for conflict resolution are needed. The conflicts primarily arise due to failure of a task in workflow execution because of underlying application, or controlling WfMS component failures or insufficient user input. So far, little progress has been reported in addressing conflict resolution in cross-organizational business processes, though its importance has been recognized. In this paper, we identify the exception handling techniques that support conflict resolution in cross-organizational settings. In particular, we propose a novel, “bundled” exception-handling approach, which supports (1) exception knowledge sharing--sharing exception specifications and handling experiences, (2) coordinated exception handling, and (3) intelligent problem solving--using case based reasoning to reuse exception handing experiences. A prototype of this exception handling mechanism is developed and integrated as a part of the METEOR Workflow Management System. An evaluation of our approach is also presented through some sample workflow applications.

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 resolution of unexpected exceptions and workflow evolution at runtime is vital for an adaptive WFMS. We have developed ADOME-WFMS via a meta-modeling approach as a comprehensive framework in which the problem of workflow exception handling can be adequately addressed. In this chapter, we present an overview of exception handling in 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.

In services-oriented agile supply chain management, more and more complex business process require for automatic and flexible ability to react to the dynamic market environ- ment. In this paper, we proposed the distributed and adaptive workflow model and implementation. The workflow model focus on the BPEL4WS based workflow composition, the DAIM-S based business domain ontology, XSRL based business process monitoring and workflow performance, semantic ECA based workflow exception handling, and petri net based workflow analyzing. In the final, we proposed intelligence multi-agents based distributed and adaptive workflow model implementation. I. INTRODUCTION Business organizations confront an increased global com- petition, which forces companies to improve their efficiency and flexibility for adapting the dynamic business environment. The agility of a company's response to customer demand has been recognized as a critical success factor to meet the global competition. Agile supply chain management has become an effective and significant measure to enhance competitive advantage of modern enterprises (1)(2). To satisfy and respond quickly to the business requirements, we proposed loosing coupled services-oriented agile supply chain management ar- chitecture. At the same time, more and more complex business process require for automatic and flexible ability to react to dynamic market and strengthen their ability to compete in global business society. To meet such requirement, we pro- posed a distributed and adaptive workflow model in services- oriented agile supply chain management. In this model, we apply BPEL4WS as services workflow definition language to composite the complex business process, and discussed the DAIM-S based business domain ontology, XSRL based business process monitoring and workflow performance, se- mantic ECA based workflow exception handling, and Petri net based workflow analyzing. In the final, We also proposed the coordinated intelligent agents based distributed and adaptive workflow implementations in services-oriented agile supply chain management.

Along with rapid development of workflow technology, on the market, there are a lot of workflow products. Workflow exception handling study in the exception of workflow, through the appropriate method to deal effectively with the exception to ensure the implementation of the workflow. Most existing research on workflow management systems (WFMS) has been focused on workflow based on well structured and well-behaved business processes. But it is devoid of the advisement of flexibility and uncertainty. This paper proposes an Agents group based approach for exception handling. Agents group is dispatched to find out the status of running processes in the system to keep track and troubleshoot them when necessary. This model describes the classification of workflow exception, and the corresponding design of different type of exception handing agents and their cooperation.

: RED is a programmed language designed, in accordance with the DOD steelman requirements, for DoD embedded computer applications. The language combines features common to most existing high level languages with new capabilities for abstract data types, exception handling, multitasking, generic definitions and access to machine-dependent facilities. This manual covers lexical structures, program structures, types, expression, statements, procedures, functions and parameters, capsules, exception handling, multitasking, overloading and generics, machine dependent facilities, advanced definitions, and low level facilities. The RED language has been designed to reduce the total life cycle cost of designing, implementing, testing, and maintaining programs. For small and medium size programs, most modern high level languages are similar. However, for large programs, such as those commonly developed for embedded applications, the facilities provided by a language become crucial. What distinguishes the RED language is that it makes it easy to express solutions to the problems encountered when developing large programs.

This paper proposes a novel architectural framework handling effective unexpected exceptions in workflow management systems (WfMS). Effective unexpected exceptions are events for which the organizations lack handling strategies. Unstructured human interventions are necessary to overcome these situations, but clash with the type of model control currently exercised by WfMS. The proposed framework uses the notion of map guidance to orchestrate these human interventions. Map guidance empowers users with contextual information about the WfMS and environment, enables the interruption of model control on the affected instances, supports collaborative exception handling and facilitates regaining model control after the exception has been resolved. The framework implementation in the Open Symphony open source platform is also described.

As model transformations are increasingly used in model-driven engineering, the dependability of model transformation systems becomes crucial to model-driven development deliverables. As any other software, model transformations can contain design faults, be used in inappropriate ways, or may be affected by problems arising in the transformation execution environment at run-time. We propose in this paper to introduce exception handling into model transformation languages to increase the dependability of model transformations. We first introduce a classification of different kinds of exceptions that can occur in the context of model transformations. We present an approach in which exceptions are modelled in the transformation language and the transformation designer is given constructs to define exception handlers to recover from exceptional situations. This facilitates the debugging of transformations at design time. It also enables the design of fault-tolerant transformations that continue to work reliably even in the context of design faults, misuse, or faults in the execution environment.

Case-based reasoning and rule-based reasoning are two techniques using the experience to resolve problems in fixture design. Each method has some shortcoming when it is employed separately. A hybrid method of case-based and rule-based reasoning can eliminate the drawbacks of each method and provide a better way for fixture design. In this paper, a retrieval mechanism of case-based reasoning in fixture design is analyzed. An improved algorithm taking the influence of fixture structure into account is proposed for calculating the similarity of fixture cases. A reuse mechanism of fixture cases is discussed from different levels and different groups. The expanded conception of fixture case is proposed. Moreover, variation level and variation method based-on the expanded fixture cases are studied. Finally, a real case is presented to demonstrate that the hybrid of case-based reasoning and rule-based intelligent variation approaches can improve the re-usability of the fixture cases.

Before a PV module is integrated into a PV system it has to be handled and transported. This handling and transport is a critical stage of the PV-modules life. In order to identify critical handling steps we accompanied the installation of PV systems and compiled a list of typical and exceptional handling situations. From these observations we developed test to be performed in the laboratory. The tests are designed to account for the mechanical installation conditions as well as for the module temperature during the installation. As a result we find that the most critical handling step is the lay down of the PV module with sunny side up. During the lay down of the module one might let drop the module on one side from a low height. For one module type we found even for a 5 cm drop height more than 5 cracked cells after the drop. In contrast a vertical drop of a framed PV module results in no cell breakage at all. Additionally the risk of cell breakage rises for static loads by at least factor two with PV module temperature of -5°C compared to 25°C. Therefore one should avoid installing PV modules below the freezing point.

Current workflow management systems do not provide adequate support for workflow modeling. Real life work processes are much richer in variations and more dynamic than is expressed in a typical workflow model. Users need to be able to adjust workloads and modify workflow models on-the-fly. In addition, data about workflow executions are analyzed with process analysis/simulation tools to evaluate design alternatives, so workflow models and data must be structured to reflect the questions that managers and designers are likely to ask. The authors present dynamic workflow management (DWM), a framework for modeling workflows that aims to satisfy these requirements. DWM provides high level packaged task templates for composing task sequences, a MOP-like structure based on dynamic memory theory to organize the task sequences into flexible workflow models, and four perspectives into a workflow model geared toward different users' interests. They illustrate these features of DWM with a case study of an interlibrary loan process and discuss its application in workflow enactment and simulation.

A concept is introduced in this article which has strong practical impact for computer aided system configuration. System configuration is a cumbersome and fault sensitive task while setting up systems in a broad range of business applications like ERP (enterprise resource planning) and other workflow-systems. Given a generic process or workflow model in YAWL-notation (yet another workflow language) or any other process modeling language like business process model and notation or WFMC (workflow management coalition), it could be stated that, by using a set of reduction rules as introduced, it is possible to generate a hierarchically structured tree of sub graphs of the workflow graph-representation. According to the notation used, authors call these sub graphs facts. The tree structure of the graph-representation on one hand and the logical relation between the branches and leafs of the tree on the other can be utilized to create a set of constraints and dependencies among the single facts. Some researchers showed that the nested branches can be associated to (predefined) questions with respect to the configuration of a workflow management system, for instance an ERP-application. They presented an algorithm which dynamically sorts the questions and answers in a maximum efficient configuration path, while working through the corresponding questionnaire. By combining the different elements as facts, constraints on questions, and configuration space, it is thus possible to algorithmically generate the efficient structured and interactive questionnaire for the configuration of workflow systems and algorithmically check the consistency (dead lock free, free of synchronization structural conflict) of the underlying workflow model. The concept was tested in the prototype of the interactive questionnaire for configuration of the web-service based ERP-Application