应用Petri网改进BPEL程序的正确性*

为了解决BPEL组合服务的正确性保证问题,提出一种基于Petri 网改善组合服务的正确性的集成方法。提出将BPEL程序转换成由PNML表示的Petri网的规则,实现由BPEL程序转换成Petri网和基于Petri网导出变迁触发序列的算法,借助一个开源工具PIPE2可分析与评价组合服务的正确性、活性等属性,所导出的触发序列可生成BPEL程序的单元测试的测试序列。案例研究表明,此方法有助于保证BPEL程序的正确性。     

基于Pi-演算的BPEL4WS Web服务组合形式化模型

Web服务组合研究领域的一个重要的问题是如何形式化描述Web服务组合,如何验证服务组合的正确性。Web服务组合的形式化模型来可以用来检查、验证Web服务组合以保证组合的正确性。Pi-演算是一种适合于Web服务组合建模的进程代数。本文介绍了P-演算的基本语法,针对目前最主要的一种描述和执行基于工作流模式的Web服务组合的规范-Web服务商业流程执行语言（Business Process Execution Language for Web Services,BPEL4WS）,定义了Pi-演算和BPEL4WS之间的概念映射,并给出了BPEL4WS的基于P-演算的形式化模型,最后通过一个案例给出了模型验证的方法。     

基于PDG图的分布式动态可执行服务组合方法

组合服务是将一系列Web服务协调地组合在一起,从而完成预期目标。组合服务按照其引擎分布可分为:集中式服务组合和分布式服务组合。分布式组合服务可以有效地解决集中式组合服务在系统可伸缩性、消息传输效率、自治性和有效负载均衡等方面的问题,将可执行全局流程等价分解成可执行本地流程,以及将服务组合和负载均衡结合集群概念,研究服务组合的QOS。这些将成为新的挑战,文中通过PDG图进行等价分解,并结合QOS,通过实验测试引擎负载,提出将负载均衡融入服务组合QOS研究思想。     

基于着色Petri网的Web合成服务会话协议

基于着色Petri网的会话协议不仅能准确地描述Web服务的业务流程特征,而且具备强大的数据承载能力。该文以BPEL4WS语言为例,在对Web服务特性进行分析的基础上,给出了基于着色Petri网的会话协议以及相应的Web合成服务设计方法。通过这种框架,可以运用成熟的Petri网技术,对Web服务模型进行进一步的分析和验证,以提高服务的正确性和可靠性。     

A model for BPEL-like languages

Web service is increasingly being applied in solving many universal interoperability problems. Business Process Execution Language (BPEL) is a de facto standard for specifying the behavior of business processes. It contains several interesting features, including scope-based compensation, fault handling and shared-labels for synchronization. In this paper we explore an observation-oriented model for BPEL-like languages, which can be used to study program equivalence. The execution states of a program are divided into five types: completed state, waiting state and divergent state, as well as error state and undo state. The last two states are especially for dealing with compensation and fault handling. Based on the formalized model, a set of algebraic laws is investigated, including traditional laws and BPEL featured laws. The concept of guarded choice is also introduced in this model, which can be used to support the transformation of a parallel program into the form of guarded choice. Two special scopes are introduced: canonical structure and compensation structure, which are used to eliminate undo and compensation construct from finite processes.     

基于流程树的BPEL4WS中流程服务动态优化方法*

针对服务流程建模语言BPEL4WS难以满足用户个性化需求也无法适应动态环境变化的问题,提出了一种动态优化BPEL4WS中流程服务的方法。该方法给出了一种Web服务交互代价计算模型,用来评价用户对Web服务的偏好程度以及实时环境下Web服务交互的现实代价。将BPEL4WS描述的服务组合流程转换为服务组合流程树,并借助领域本体对流程树节点进行语义检查,消除流程树中不合法的流程组合。通过深度优先遍历流程树,利用单亲遗传算法对流程服务进行优化组合。最后给出应用算例,并对用来优化组合流程服务的单亲遗传算法的适用性与     

MicroMAIS: executing and orchestrating Web services on constrained mobile devices

Mobile devices with their more and more powerful resources allow the development of mobile information systems in which services are not only provided by traditional systems but also autonomously executed and controlled in the mobile devices themselves. Services distributed on autonomous mobile devices allow both the development of cooperative applications without a back‐end infrastructure and the development of applications blending distributed and centralized services. In this paper, we propose MicroMAIS: an integrated platform for supporting the execution of Web service‐based applications natively on a mobile device. The MicroMAIS platform is composed of mAS and μ‐BPEL. The former allows the execution of a single Web service, whereas the latter permits the orchestration of several Web services according to the WS‐BPEL standard. Copyright © 2011 John Wiley & Sons, Ltd.     

WS-BPEL服务可替换性分析

在开放、动态、多变的Internet环境下,服务替换是保证面向服务的软件系统持续可信的重要手段.现有方法大多在控制流模型层面上进行BPEL服务的可替换性分析,而较少考虑BPEL服务中的数据因素,并且当BPEL服务中存在对分布服务的异步调用时,现有方法过于保守.为此,本文提出一种基于程序依赖图的BPEL服务可替换性分析方法,该方法综合考虑了BPEL服务中的控制依赖、数据依赖、异步调用依赖以及交互依赖关系,从而可有效应对BPEL服务的可替换性问题.我们使用一个旅行代理BPEL服务替换案例阐明了本文方法的有效性和可行性.     

基于BPEL4WS的Web服务整合研究

业务流程执行语言（BPEL4WS）是整合Web 服务的标准，其作用是将一组现有的服务整合起来，从而定义一个新的 Web 服务。首先介绍了业务流、工作流、以及BPEL4WS在Web服务建模方面的基本概念，建立了BPEL4WS整合Web服务模型，提出了组合服务的方法和过程。最后通过实例证明了BPEL4WS服务整合的实用性。     

基于接口自动机的BPEL4WS Web服务组合形式化模型

介绍了接口自动机的基本语法,针对目前最主要的一种描述和执行基于工作流模式的Web服务组合的规范——Web服务商业流程执行语言 (business process execution language for Web services,BPEL4WS),定义了接口自动机和BPEL4WS之间的概念映射,并给出了BPEL4WS的基于接口自动机的形式化模型,最后通过一个案例给出了BPEL4WS到接口自动机的映射及验证的方法。     

基于翻译模式的BPEL到LOTOS映射方法研究

为了实现由BPEL描述的Web服务组合到LOTOS的自动化转换, 提出一种基于翻译模式的转换算法。从BPEL语言的XML schema定义出发, 分析BPEL本身的语言结构, 得到BPEL语言的产生式。再根据BPEL到LOTOS的语义映射规则, 设计BPEL到LOTOS的翻译模式。同时, 在基本映射规则之上, 给出BPEL到LOTOS的数据类型和故障处理机制的转换规则。最后结合Web服务实例, 验证该工具的可行性。     

Linking denotational semantics with operational semantics for web services

Web Services have become more and more important in these years, and BPEL4WS (BPEL) is a de facto standard for the web service composition and orchestration. It contains several distinct features, including the scope-based compensation and fault handling mechanism. The denotational semantics and operational semantics have been explored for BPEL. The two semantic models should be consistent. This paper considers the linking of these two semantics. Our approach is to derive the denotational semantics from operational semantics for BPEL, which aims for the consistency of the two models. Moreover, the derivation can be applied in exploring the program equivalence easily, especially for parallel programs.     

一种基于CPN的运行时监控服务交互行为的方法

BPEL对Web服务组合的描述特性使得它很难表达和分析服务组合中的交互行为属性.这些行为属性需要遵循一定的交互协议.然而良定义的交互协议还是容易受到侵犯,这将导致服务组合进程产生状态不一致的问题.为了解决这类实际交互行为与其服务组合描述之间的不一致性问题,提出了一种由BPEL描述自动构造运行时监控器的方法.首先提出了一种基于有色Petri网(CPN)的形式化表示模型以及服务组合规约到模型的映射方法,用于精确表达从BPEL流程描述中提取的服务交互行为规约.然后,描述了由CPN形式化表示模型生成运行时监控器的方法.该运行时监控器能够捕获所有进出服务组合进程的交互消息,并且检测是否存在违背交互协议的行为.     

基于BPEL的易货交易系统安全性研究

为解决因信用额度取代现金进行网上易货交易而造成的安全性问题,在电子商务领域引入Web服务与BPEIAWS规范,分析网上易货交易过程中业务流程实际模型;在以SSH及Ajax技术实现的华贸易货系统基础上.引进银行信用和结算服务,使用Web Services和BPEL技术设计业务流程,并依托监控软件BPM实现流程的自动化执行与安全性监控;通过Irrelevant和Inconsistent两种优化方式改善监控算法,提高监控效率和准确性.     

Orchestrating Web Services with BPEL

Effective Web services demand careful synchronization on various abstraction levels. The Business Process Execution Language supports modeling and executing business processes from both the user and systems perspectives. In this way, Web services application developers can use BPEL to orchestrate service interactions in a global system view and to manage individual interactions based on outside events. More and more Web service providers are using BPEL to integrate their services independently of vendors and related programming languages. In this column, we introduce BPEL and presents some guidelines for using it in your Web services management.     

BPEL组合服务可信性评估方法研究

提出了一种基于数据依赖的Web服务编程语言(business process execution language for Web services,BPEL4WS,简称BPEL)的可信性评估方法。利用扩展BPEL控制流图(extensible BPEL flow graph,XBFG)对BPEL进行建模,通过建模获得组件间的直接和间接数据依赖关系,并构造依赖链用以计算组件的信任值。根据BPEL组合服务的控制结构,在XBFG上通过约减规则对BPEL组合服务可信性进行评估。实验结果表明,基于数据依赖的组合服务可信性评估方法可以有效地评估BPEL组合服务的可信性,并且这种评估方法较为稳定,不会随着组件数量的增加而影响评估结果。     

A Calculus for Generation, Verification and Refinement of BPEL Specifications

Business Process Execution Language for Web Services (WS-BPEL) is the emerging standard for designing Web Services compositions. In this context, formal methods can contribute to increased reliability and consistency in the BPEL design process. In this paper we propose an approach based on the HAL Toolkit that allows verification of the correctness of the behavior of a π-based specification of interacting Web Services, and generates the BPEL processes that have the same behavior. This correlation based on two-way mapping between the π-based orchestration calculus and BPEL. This approach facilitates the verification and refinement process and may be applied to any BPEL implementation.