Geração de processos WS-BPEL com base em um algoritmo de reescrita de regras

Web services are computational solutions designed according to the principles of Service Oriented Computing. Web services can be built upon pre-existing services available on the Internet by using composition languages. We propose a method to generate WS-BPEL processes from abstract specifications provided with high-level control-flow information. The proposed method allows the composition designer to concentrate on high-level specifi- cations, in order to increase productivity and generate specifications that are independent of specific web services. We consider service orchestrations, that is compositions where a central process coordinates all the operations of the application. The process of generating compositions is based on a rule rewriting algorithm, which has been extended to support basic control-flow information.We created a prototype of the extended refinement method and performed experiments over simple case studies

BPEL引擎监控平台的设计与实现

WS-BPEL作为WEB服务复合事实上的标准正引起越来越多的关注，它可以用来整合物理上分布的服务，构建复杂的业务流程。复合服务的执行依赖于分布的自治的第三方服务，其实际行为可能与预先指定的行为约束不一致；此外，由于复合服务的动态性和灵活性，其本身在运行期间可能发生动态调整，以适应不断变化的业务环境，因此需要对复合服务的行为在运行期进行连续的监控，保证复合服务的正确执行。同时，通过对复合服务的运行时监控，可以获取执行期间的各种性能信息，从而为流程的优化和动态的服务选择提供依据。 本文首先对业务流程运行时的监控需求进行了分析，然后针对这些监控需求，结合BPEL流程的特点，设计了一种新型的基于事件的监控需求描述语言Mon-BPEL，它可以精确的刻画功能性和非功能性的监控需求。相对于其他基于事件的监控需求描述语言(如 Event Calculus，Past LTL等)，Mon-BPEL可以方便的刻画流程执行事件序列之间的时序关系，同时，它具有简洁易懂，用户友好等特点。 此外，本文研究了基于AOP技术的业务流程监控机制。论文设计了一种针对BPEL语言的AOP扩展方案，以支持对业务流程运行期的动态监控。通过将监控需求映射为方面，从而分离了关注点，降低了业务流程开发的复杂度，提高了流程的可维护性。接着给出了Mon-BPEL监控需求表达式的的自动机语义，并基于自动机理论对监控需求表达式进行计算，检查指定的监控需求是否违背。最后，论文探讨了Aspect的动态编织机制，将监控功能引入BPEL引擎。 论文最后给出了监控平台在OnceBPEL引擎中的实现，并将前面提到的研究成果引入其中,通过实验对系统的功能及性能进行了测试与评估。

BPMN与BPEL双向转换系统的设计与实现及其应用

随着SOA和业务流程管理BPM技术日益成熟，基于业务流程的开发得到越来越广泛的应用。BPMN是由国际标准组织BPMI所制定的业务流程描述语言，制定了标准化的图形符号用于流程的设计和交流。WS-BPEL是面向服务计算中服务复合层重要的技术规范，WS-BPEL支持通过组合分布异构的服务形成复杂的业务流程。BPMN和BPEL模型之间存在差异，跨越两者之间的鸿沟实现无缝转换是当前服务计算中的关键问题之一。现有的BPMN到BPEL转换方法对用户建模限制太大，并且转换后的BPEL不能直接部署和运行，自动化程度不高。现有BPEL到BPMN转换方法缺少对复杂BPEL结构的转换。 针对这些问题，论文设计了一套双向模型转换方法。首先分析了现有BPMN到BPEL的转换方法。然后根据分析结果对已有的BPMN到BPEL转换方法进行扩展，并着重解决了路由OR和并发多实例Multi-instance的语义分析和转换这一难点问题，减少了用户建模时的限制，转换得到的可直接执行的BPEL，提高了自动化程度。在此基础上，设计了BPEL到BPMN的转换方法，采取自上而下的扁平化策略来将嵌套块结构的BPEL控制流转换成为平整无层次的流程图结构，其中分析了Link设置不同条件时的语义并分别转换到对应的BPMN结构，解决了复杂BPEL结构的转换。 最后，我们在流程设计平台OnceBPD（Once Business Process Designer）实现了双向转换功能，能够将BPMN模型转换为BPEL模型，得到的BPEL文件可以部署和运行在OnceBPEL流程执行引擎。还可以将BPEL模型装换为BPMN模型，并应用于OnceBPEL引擎监控信息的可视化，实现了在OnceBPD中直观、形象的显示流程监控。

事件驱动的BPEL引擎架构设计与实现

WS-BPEL(Web Service Business Process Execution Language，简称BPEL)是Web服务规范族中服务复合层的重要标准。BPEL支持通过对Web服务的编制(Orchestration)来构建业务流程，从而使编程人员能够集中关注业务逻辑。BPEL引擎系统是一个支持BPEL语言描述的业务流程运行的服务器中间件系统，使用BPEL引擎可以执行BPEL语言编写的业务流程。作为一个网络服务器系统，BPEL引擎将不可避免的处理大量的并发请求。如何设计实现BPEL引擎使之能高效的处理并发将是高性能BPEL引擎设计的关键问题。 并发服务器系统通常采用多线程和事件驱动两种并发模型。传统上大多数服务器软件都建立在多线程(或多进程)模型的基础上。但在高负载条件下，过多的线程和线程间的上下文切换会造成系统较大的开销，这些开销是导致系统性能下降的主要原因。事件驱动模型是一种只采用少量固定数量线程的并发模型，一般说来，它的伸缩性更好，并且有更高的处理效率。 本文对高并发服务器系统中所使用的事件驱动模型进行了分析和研究，并且结合BPEL语言规范的特点，提出了事件驱动的BPEL引擎实现技术方案。论文重点研究了BPEL事件结构和有限状态机(Finite State Machine，简称FSM)刻画BPEL流程和活动行为的原理，针对BPEL语言语法特点，构造了完整的BPEL FSM模型，包括了状态空间和基于ECA(Event-Condition-Action)模式的状态转移规则。 在基于事件驱动模型的BPEL引擎架构原理的指导下，我们设计并实现了基于事件驱动模型的OnceBPEL2.0引擎系统。并且，我们对采用多线程模型实现的OnceBPEL1.0系统和采用事件驱动模型实现的OnceBPEL2.0系统进行了性能测试和分析比较。从我们的测试数据和分析结果可以看出，采用事件驱动模型的OnceBPEL2.0系统比采用多线程模型的OnceBPEL1.0有了较大的性能提升。

Introduction to the First International Workshop on Empirical Research in Business Process Management (ER-BPM 2009)

Providing effective IT support for business processes has become crucial for enterprises to stay competitive. In response to this need numerous process support paradigms (e.g., workflow management, service flow management, case handling), process specification standards (e.g., WS-BPEL, BPML, BPMN), process tools (e.g., ARIS Toolset, Tibco Staffware, FLOWer), and supporting methods have emerged in recent years. Summarized under the term “Business Process Management” (BPM), these paradigms, standards, tools, and methods have become a success-critical instrument for improving process performance.

Aggregate quality of service computation for composite services

This paper addresses the problem of computing the aggregate QoS of a composite service given the QoS of the services participating in the composition. Previous solutions to this problem are restricted to composite services with well-structured orchestration models. Yet, in existing languages such as WS-BPEL and BPMN, orchestration models may be unstructured. This paper lifts this limitation by providing equations to compute the aggregate QoS for general types of irreducible unstructured regions in orchestration models. In conjunction with existing algorithms for decomposing business process models into single-entry-single-exit regions, these functions allow us to cover a larger set of orchestration models than existing QoS aggregation techniques.

Implementing process views in the web service environment

Web service and business process technologies are widely adopted to facilitate business automation and collaboration. Given the complexity of business processes, it is a sought-after feature to show a business process with different views to cater for the diverse interests, authority levels, etc., of different users. Aiming to implement such flexible process views in the Web service environment, this paper presents a novel framework named FlexView to support view abstraction and concretisation of WS-BPEL processes. In the FlexView framework, a rigorous view model is proposed to specify the dependency and correlation between structural components of process views with emphasis on the characteristics of WS-BPEL, and a set of rules are defined to guarantee the structural consistency between process views during transformations. A set of algorithms are developed to shift the abstraction and concretisation operations to the operational level. A prototype is also implemented for the proof-of-concept purpose. © 2010 Springer Science+Business Media, LLC.

基于状态方面的Web服务动态替换

随着面向服务计算技术的成熟,服务复合已成为Internet上开发企业间业务协作的一种新模式,WS-BPEL是服务复合事实上的标准.但是由于复合服务所依赖的第三方伙伴服务的分布、自治和松散耦合等特性,在执行过程中易受到伙伴服务失效的影响,可靠性无法得到保证,因此需要支持在运行时对伙伴服务进行动态替换.目前的BPEL规范只提供有限的服务替换功能,当与伙伴服务的交互涉及到一系列有状态的会话操作时,服务替换就更加复杂.通过对面向方面的研究,提出面向BPEL语言的状态方面扩展.通过状态方面,记录与伙伴服务交互过程中的会话信息.在伙伴服务失效时,通过透明地替换伙伴服务,使得与当前伙伴服务的会话信息传播到功能等价的另一个伙伴服务上,以保证流程的正常执行.通过该方法,使得BPEL流程具有一定的自愈能力,增强了流程执行的可靠性.

Formalizing languages for service oriented computing

Service Oriented Computing is a new programming paradigm for addressing distributed system design issues. Services are autonomous computational entities which can be dynamically discovered and composed in order to form more complex systems able to achieve different kinds of task. E-government, e-business and e-science are some examples of the IT areas where Service Oriented Computing will be exploited in the next years. At present, the most credited Service Oriented Computing technology is that of Web Services, whose specifications are enriched day by day by industrial consortia without following a precise and rigorous approach. This PhD thesis aims, on the one hand, at modelling Service Oriented Computing in a formal way in order to precisely define the main concepts it is based upon and, on the other hand, at defining a new approach, called bipolar approach, for addressing system design issues by synergically exploiting choreography and orchestration languages related by means of a mathematical relation called conformance. Choreography allows us to describe systems of services from a global view point whereas orchestration supplies a means for addressing such an issue from a local perspective. In this work we present SOCK, a process algebra based language inspired by the Web Service orchestration language WS-BPEL which catches the essentials of Service Oriented Computing. From the definition of SOCK we will able to define a general model for dealing with Service Oriented Computing where services and systems of services are related to the design of finite state automata and process algebra concurrent systems, respectively. Furthermore, we introduce a formal language for dealing with choreography. Such a language is equipped with a formal semantics and it forms, together with a subset of the SOCK calculus, the bipolar framework. Finally, we present JOLIE which is a Java implentation of a subset of the SOCK calculus and it is part of the bipolar framework we intend to promote.

Implementação de um modelo baseado em XML para suporte da dinâmica processual de negócio

Este artigo descreve um modelo para implementação de plataformas dinâmicas de negócio, exclusivamente baseadas em tecnologias XML. Apresenta um caso real que implementa as suas diversas camadas, apresentação, lógica e dados, em XML. A comunicação entre camadas é assegurada por serviços Web (WS), tornando esta arquitectura orientada aos serviços (SOA). O modelo proposto sustenta toda a programação do processo de negócio numa linguagem de alto nível, o WS-BPEL, proporcionando, desse modo, condições de adaptação ao dinamismo exigido pelo negócio da organização e à heterogeneidade dos sistemas. O caso real é de uma secretaria electrónica que surge no contexto dos portais Web universitários. O sistema desenvolvido visa oferecer um conjunto de serviços para acesso a informação e para o despoletar de acções computacionais e/ou humanas.

An introduction to service choreographies (Servicechoreographien – eine Einführung)

Service oriented architecture (SOA) is an architectural style for building software systems based on services. Especially in those scenarios where services implement business processes, complex conversations between the services occur. Service choreographies are a means to capture all interaction obligations and constraints from a global perspective. This article introduces choreographies as an important artifact for SOA, compares them to service orchestrations and surveys existing languages for modeling them.