基于事务和Agent联邦的工作流异常处理机制

异常处理和恢复是工作流管理系统(workflow management system,WFMS)不可缺少的部分.在把工作流异常分为技能级异常、活动级异常和工作流级异常的基础上,结合工作流中活动的事务性,提出了基于事务的异常处理策略,并在基于Agent联邦中各Agent的合作性,提出了异常的检测方法和传递机制,提高了系统处理异常的灵活性.     

基于CPN的工作流异常处理模型设计

工作流异常处理是工作流管理系统中的重要组成部分,但是它的实现既复杂又耗时。为了支持面向服务的工作流,层次化地描述异常处理,提出一种基于CPN的异常处理模型。在形式化描述工作流异常的基础上,采用补偿法作为异常处理方式,详细描述了处理结构中的异常监控、异常分析和补偿案例执行三个子过程。结合茶餐厅的运营模型的仿真实验证明了该模型可有效地分离工作流的异常处理逻辑和运行逻辑,并支持工作流管理系统的实施。     

Techniques for Supporting Dynamic and Adaptive Workflow

The unpredictability of business processes requires that workflowsystems support exception handling with the ability to dynamicallyadapt to the changing environment. Traditional approaches to handlingthis problem have fallen short, providing little support for change,particularly once the process has begun execution. Further,exceptions vary widely in their character and significance,challenging the application of any single approach to handling them.We briefly discuss the classification of exceptions, highlightingdiffering impacts on the workflow model. Based on this discussion, wesuggest principal goals to address in the development of adaptiveworkflow support, including strategies for avoiding exceptions,detecting them when they occur, and handling them at various levels ofimpact. We then identify a number of specific approaches to supportingthese goals within the design of a workflow system infrastructure.Finally, we describe the implementation of many of these approaches inthe Endeavors workflow support system.     

一种实用的工作流异常处理机制

提出了一种基于虚拟组织集成框架IFVO的工作流管理系统的异常处理机制,深入分析了工作流系统异常处理的相关问题,并结合实例阐述了该机制的实现和应用。     

Exception Handling for Conflict Resolution in Cross-Organizational Workflows

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.     

Mining and reasoning on workflows

Today's workflow management systems represent a key technological infrastructure for advanced applications that is attracting a growing body of research, mainly focused in developing tools for workflow management, that allow users both to specify the "static" aspects, like preconditions, precedences among activities, and rules for exception handling, and to control its execution by scheduling the activities on the available resources. This paper deals with an aspect of workflows which has so far not received much attention even though it is crucial for the forthcoming scenarios of large scale applications on the Web: providing facilities for the human system administrator for identifying the choices performed more frequently in the past that had lead to a desired final configuration. In this context, we formalize the problem of discovering the most frequent patterns of executions, i.e., the workflow substructures that have been scheduled more frequently by the system. We attacked the problem by developing two data mining algorithms on the basis of an intuitive and original graph formalization of a workflow schema and its occurrences. The model is used both to prove some intractability results that strongly motivate the use of data mining techniques and to derive interesting structural properties for reducing the search space for frequent patterns. Indeed, the experiments we have carried out show that our algorithms outperform standard data mining algorithms adapted to discover frequent patterns of workflow executions.     

基于优先级的柔性时空工作流异常处理

针对当前工作流异常处理独立于工作流流程的情况,提出一种基于优先级过滤的工作流异常处理方法,通过定义异常处理优先级,结合工作流的整体流程,过滤次要异常,优先处理重要异常,实现工作流异常有效处理。并通过一个技术文档的实例,验证该方法确能够提高工作流异常处理的有效性,降低异常处理对整体流程的影响。     

Web interface-driven cooperative exception handling in ADOME workflow management system

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.     

C++程序中异常处理的分析与测试技术研究

异常处理机制是一种运行时错误通知机制，将程序的正常控制代码和错误处理代码分离．然而异常机制的引入使得程序控制信息变得更为复杂；且开发人员一般难以熟练使用它，导致程序中会潜伏许多异常错误．扩展已有的显式异常分析技术，对隐式异常也进行了全面的分析并提出了过程间（内）控制流图的构造方法，并以此为基础给出了一个C＋＋程序健壮性改进模型．同时还提出了针对异常的两种动态测试策略：基于约束求解的异常测试策略和统计结构性异常测试策略．最后实现了一个初步的异常分析与测试原型工具并进行了初步实验分析，其结果表明本文提出的分析与测试方法对程序质量有较大程度的提高．     

Exception Handling in Workflow Systems

In this paper, defeasible workflow is proposed as a framework to support exception handling for workflow management. By using the justified ECA rules to capture more contexts in workflow modeling, defeasible workflow uses context dependent reasoning to enhance the exception handling capability of workflow management systems. In particular, this limits possible alternative exception handler candidates in dealing with exceptional situations. Furthermore, a case-based reasoning (CBR) mechanism with integrated human involvement is used to improve the exception handling capabilities. This involves collecting cases to capture experiences in handling exceptions, retrieving similar prior exception handling cases, and reusing the exception handling experiences captured in those cases in new situations.     

工作流异常处理的形式描述

异常处理是工作流执行中要解决的主要问题之一，清楚地描述异常处理的过程是最终得到实现的基础。Petri-net对工作流的描述适合于对过程定义进行正确性验证和评价，但描述各种不同条件下的处理策略却很繁琐，采用了一种直观的描述方法对异常处理过程中的元素，即活动、异常处理策略以及处理措施进行了形式化描述，特别是对不同处理策略下的处理过程进行了描述。结合消息机制，分析了一个异常事件出现时，如何处理一个活动实例产生的中间数据，并对事务处理和异常处理的补偿策略进行了比较。描述方法为编码实现提供了很大的方便。     

A rule-based approach to proactive exception handling in business processes

Effectively handling exceptions in business process is an important capability of enterprises in the current global market environment, since their business processes are becoming more complex. Effective exception handling requires systematic support for the entire scope of exception handling: from exception prediction to exception prevention, and from exception detection to exception resolution. Most existing research approaches to exception handling in business process management and workflow areas have focused on reactive exception handling which resolves exceptions only after their occurrences. Therefore, a proactive exception handling approach is required to predict and prevent business process exceptions as early as possible before they occur, and detect and resolve exceptions as soon as possible after they occur. This paper presents comprehensive behavioral, functional, and informational requirements for proactive exception handling from the lifecycle perspective. Then, it proposes a rule language for proactive exception handling based on the requirements. The proposed rule language will enable effective and flexible exception handling by providing the information required for the entire scope of exception handling, especially, for exception prediction and prevention. Finally, the paper illustrates and validates the rule language with an example of exception prevention and a prototype system.     

Extended event–condition–action rules and fuzzy Petri nets based exception handling for workflow management

Exception handling plays a key role in dynamic workflow management that enables streamlined business processes. Handling application-specific exceptions is a knowledge-intensive process involving different decision-making strategies and a variety of knowledge, especially much fuzzy knowledge. Current efforts in workflow exception management are not adequate to support the knowledge-based exception handling. This paper proposes a hybrid exception handling approach based on two extended knowledge models, i.e., generalized fuzzy event–condition–action (GFECA) rule and typed fuzzy Petri net extended by process knowledge (TFPN-PK). The approach realizes integrated representation and reasoning of fuzzy and non-fuzzy knowledge as well as specific application domain knowledge and workflow process knowledge. In addition, it supports two handling strategies, i.e., direct decision and analysis-based decision, during exception management. The approach fills in the gaps in existing related researches, i.e., only providing the capability of direct exception handling and neglecting fuzzy knowledge. Based on TFPN-PK, a weighted fuzzy reasoning algorithm is designed to address the reasoning problem of uncertain goal propositions and known goal concepts by combining forward reasoning with backward reasoning and therefore to facilitate cause analysis and handling of workflow exceptions. A prototype system is developed to implement the proposed approach.     

A novel general framework for automatic and cost-effective handling of recoverable temporal violations in scientific workflow systems

Due to the complex nature of scientific workflow environments, temporal violations often take place and may severely reduce the timeliness of the execution's results. To handle temporal violations in an automatic and cost-effective fashion, two interdependent fundamental issues viz. the definition of fine-grained recoverable temporal violations and the design of light-weight effective exception handling strategies need to be resolved. However, most existing works study them separately without defining a comprehensive framework. To address such a problem, with the probability based temporal consistency model which defines the range of recoverable temporal violations, a novel general automatic and cost-effective exception handling framework is proposed in this paper where fine-grained temporal violations are defined based on the empirical function for the capability lower bounds of the exception handling strategies. To serve as a representative case study, a concrete example exception handling framework which consists of three levels of fine-grained temporal violations and their corresponding exception handling strategies is presented. The effectiveness of the example framework is evaluated by large scale simulation experiments conducted in the SwinDeW-G scientific grid workflow system. The experimental results demonstrate that the example framework can significantly reduce the overall average violation rates of local temporal constraints and global temporal constraints to 0.127% and 0.167% respectively.     

一种工作流自适应容错模型

设计了一种在工作流子系统中,可根据工作流的异常类型自动选择容错策略的自适应容错模型,针对不可恢复异常采用了事务补偿机制的容错策略进行异常处理,而针对可恢复异常采用了自动恢复的容错策略进行异常处理。详细描述了该模型所采用的消息队列、事务补偿机制、自动恢复机制。     

An environment for designing exceptions in workflows

When designing a workflow schema, the workflow designer must often explicitly deal with exceptional situations, such as abnormal process termination or suspension of task execution. This paper shows how the designer can be supported by tools allowing him to capture exceptional behavior within a workflow schema, by reusing an available set of pre-configured exceptions skeletons. Exceptions are expressed by means of triggers, to be executed on the top of an active database environment. In particular, the paper deals with the handling of typical workflow exceptional situations which are modeled as generic exception skeletons to be included in a new workflow schema by simply specializing or instantiating them. Such skeletons, called patterns, are stored in a catalog; the paper describes the catalog structure and its management tools constituting an integrated environment for pattern-based exception design and reuse.     

用着色Petri网建模工作流模式

工作流模式指在工作流过程模型中反复出现的过程基本构造,是衡量工作流建模语言在控制流方面的表达能力和适用性的重要标准,目前市场上的工作流引擎对其支持得并不好。本文重点阐述了基于着色Petri网的工作流建模语言对当前流行的20种工作流模式的支持情况。结果表明,该语言不仅能很好地支持全部模式,而且具有建模简洁、准确的特点。同其它建模语言相比,用着色Petri网建模工作流模式具有较好的灵活性和扩展性。它也为如何使基于着色Petri网的工作流引擎能够正确、有效地支持全部20种工作流模式提供了有意义的指导。     

工作流系统中的一种异常处理机制

文中通过对工作流系统可能出现的异常情况进行较详细的分析，提出了利用规则库进行异常处理的模型，并对异常处理规则的数据结构进行了较深入的探讨。     

工作流管理系统异常处理的方法与层次

工作流技术在信息处理领域的应用越来越受到重视,但应用中环境和用户要求的不断发展和变化需要工作流管理系统具有灵活的处理能力,工作流系统的异常处理正是要解决这种不断要求的变化。文章介绍了工作流异常处理的应用范围,总结了不同的应用方法,从系统的角度提出了工作流未来的异常处理层次,并在研究可适应性工作流技术方面进行了探讨。     

基于异常检测和处理的动态适应性工作流

异常的检测和处理是工作流系统执行过程中必须解决的关键性问题之一.给出了异常的分类,并给出了异常自身及其处理方法的形式化描述;实现了利用消息传递机制作为异常的检测方法,并结合异常适应库来提供异常处理的执行策略和处理措施;通过为相应的措施设计特定的操作原语,从而为其转变为实际的编码提供了可能.