基于WS-BPEL 的Web 服务组合技术

随着Web服务技术的不断发展,越来越多的Web服务已经发布在互联网上。然而独立的Web服务功能通常有限,不能满足用户或企业实际应用的需求。因此,Web服务的组合显得越来越重要。介绍了Web服务组合和WS-BPEL的相关知识,使用最新的业务流程执行语言WS-BPEL描述业务流程,在J2EE集成开发环境下设计并实现了基于业务流程思想的贷款审批应用实例,在Web服务执行引擎Active BPEL上进行部署,对Web服务进行了有效的组合。     

Quality-of-service oriented web service composition algorithm and planning architecture

In the next few decades, it is expected that web services will proliferate, many web services will offer the same services, and the clients will demand more value added and informative services rather than those offered by single, isolated web services. As the result, the problem of synthesizing web services of high quality will be raised as a prominent issue. The clients will face the trouble of choosing or creating composition plans, among numerous possible plans, that satisfy their quality-of-service (QoS) requirements. Typical QoS properties associated with a web service are the execution cost and time, availability, successful execution rate, reputation, and usage frequency. In engineering perspective, generating the composition plan that fulfills a client’s QoS requirement is a time-consuming optimization problem. To resolve the problem in a timely manner, we propose a constraint satisfaction based web service composition algorithm that combines tabu search and simulated annealing meta-heuristics. As an implementation framework of the algorithm, we suggest a QoS-oriented web service composition planning architecture. The architecture maintains expert made composition schemas in a service category and assists the client as pure user to choose the one he/she wants to use. The main modules of the architecture are composition broker and execution plan optimizer. With the aid of the UDDI server, the composition broker discovers candidate outsourced web services for each atomic process of the selected schema and gathers QoS information on the web services. After that, the execution plan optimizer runs the web service composition algorithm in order to generate a QoS-oriented composition plan. The performance of the algorithm was tested in a simulated environment.     

Context-Aware Web Service Composition based on AI Planning

A web service is an application that is published on the web and can be discovered and used automatically. In many cases, a web service cannot provide the capability that the user has requested. Therefore, according to the user request, it should be possible to combine various services and produce a new composite service for the user request. Context is the information that can be used to characterize the situation of an entity. In this paper, we present our context model for web service composition and implement the newly proposed framework for context-aware web service composition and show how the newly proposed framework reduces the number of failures and composition time.     

网格服务的合成模型研究

开放网格体系结构OGSA规范通过整合网格和Web服务技术确定了网格服务分布式系统框架，但其中关于网格服务合成的方面并没有定义相应的规范，业务流程执行语言BPEL4WS是应用于Web服务上的服务合成规范。通过分析网格服务和Web服务的异同，设计出一种可行的模型，解决了BPEL4WS不支持网格服务中部分特性的问题，从而可以将BPEL4WS应用于网格服务合成上。     

Eine Dienstgüte unterstützende Webservice-Architektur für flexible Geschäftsprozesse

Web services as a technology to enable distributed business processes gain in importance. However, the support of Quality of Service (QoS) is crucial in this context. Thus, we present an integrated web service architecture with comprehensive QoS support. The architecture we introduce in this paper supports the assessment of web services to assure that only web services will be used in critical business processes that satisfy the requirements defined by the user. The selection and execution of a certain web service depends on its QoS-properties that must be guaranteed in Service Level Agreements (SLAs). The compliance with SLAs is monitored by the system as well. Furthermore we introduce a prototypical implementation of our web service architecture.     

A simulation-based approach for dynamic process management at web service platforms

Web services technology is being adopted as a viable deployment approach for future distributed software systems that enable business-to-business and business-to-consumer interactions across the open and dynamic internet environment. Recent research is focused on developing support technologies for web service discovery, on-demand service composition, and robust execution to facilitate web services based deployment of business processes. Developing techniques to cope with the volatile and open nature of the web during execution of composite services at the service platform is essential for delivering reliable and acceptable performance in this new process delivery framework. In this paper, we propose a simulation-based framework to guide scheduling of composite service execution. Online simulation of the dynamics of the open environment is used for scheduling service requests at the service platform. Comparison of the look-ahead simulation for different scheduling policies with the current execution state provides guidelines for service execution in order to cope with system volatility. We have implemented a prototype of the proposed framework and illustrate the feasibility of our approach with experimental studies.     

服务时间随机条件下服务组合质量分析

本文分析采用业务过程执行语言（BPEL2WS）描述的web服务组合的执行时间,给出在服务执行时间随机情况下,根据单个服务的执行时间概率分布密度和BPEL2WS模型的结构求解web服务组合执行时间的概率分布密度函数的算法。根据概率密度函数可以求得业务过程执行时间在任意时限内的概率,从而可以根据给定的概率条件优化组合服务,使得服务执行成本最低．最后通过一个应用实例验证了算法的有效性。     

An experience report on developing an automated web services platform

Web services have attracted significant industry interest as a low-cost and flexible technology alternative to distributed object and proprietary message-oriented methods for delivery of on-demand business processes, enabling intra-organizational systems integration, and in the long term, development of dynamic inter-organizational process networks that may revolutionize B2C and B2B e-commerce. Exploiting this latent potential of web services technology requires the development of automated techniques for scalable and reliable service composition and execution in web service platforms. In this paper, we summarize our experience in developing an architectural framework for web services platforms, called Integrated Service Planning and Execution architecture (ISP & E). The use of recent advances in AI planning, learning and semantic web technologies for service composition, reliable service execution, transaction synthesis, and model-driven deployment of services is discussed. Furthermore, we discuss implications for and research issues in the development of web services based systems to aid e-business.     

Meta web service: building web-based open decision support system based on web services

Web services are currently one of the trends in network-based business services, which intuitively will be applied to build a semantic web-based decision support system (DSS). Since web services are self-contained, modular business process applications, based on open standards, enable integration models for facilitating program-to-program interactions. Decision modules in a semantic web-based DSS can be viewed as a web service. However, according to the current features, web services know only about themselves, they are neither autonomous, nor are they designed to use ontologies; they are passive until invoked, and they do not provide for composing functionalities. These lead to the motivation on building a sophisticated web service to contain these features and to utilize web services on behalf of the user. This paper aims to propose a new concept of Meta Web Service, a web service-based DSS. The meta web service understands the user's problem statement with ontology, performs web service discovery, web service composition, and automatically generates codes for composite web service execution. Case-based reasoning is applied to quickly find past histories of successful service compositions. A prototype of research web service has been developed to show the feasibility of the proposed idea.     

A dual-layered model for web services representation and composition

Nowadays more and more companies and organizations implement their business services in the Internet due to the tremendous progress made recently in the field of Web services. It becomes possible to publish, locate and invoke applications across the Web. Thus, the ability to select efficiently and integrate at runtime services located in different sites on the Web is an important issue. In some situations, if no single Web service can satisfy the request of the user, there should be a possibility to combine existing services together in order to meet the user’s request. This paper provides a dual-layered model for web services, where the first model layer captures the high-level functional specifications (namely goals, achievement contexts, and external behaviours), and the second model layer captures the low-level functional specifications (namely interfaces). This model allows the service composition process to be performed on both high-level and low-level specifications. We also introduce the composition operators (both high-level and low-level) to allow composition of virtual services.     

Web Service Diagnoser Model for managing faults in web services

Reliability is an important criterion to facilitate extensive deployment of web service technology for commercial business applications. Run-time monitoring and fault management of web services are essential to ensure uninterrupted and continuous availability of web services. This paper presents WISDOM (Web Service Diagnoser Model) a generic architecture for detecting faults during execution of web services. Policies have been proposed to describe the intended behavior of web services and faulty behavior would be detected as deviations or inconsistencies with respect to the specified behavior. The model proposes the use of monitoring components in service registries and service providers to detect run-time faults during publishing, discovery, binding and execution of web services. An independent fault diagnoser is proposed to coordinate the individual monitoring components and also act as a repository for the specified web service policies. The proposed model has been tested with a sample web service application and the results obtained are presented.     

Towards a classification of web service feature interactions

The rapid introduction of new web services into a dynamic business environment can lead to undesirable interactions that negatively affect service quality and user satisfaction. In previous work, we have demonstrated how such interactions between web services can be modeled as feature interactions. In this paper, we outline a classification of web service feature interactions. The goals of this classification are to understand the scope of the feature interaction problem in the web services domain, and to propose a benchmark against which to assess the coverage of solutions to this problem. As there is no standard set of web services that one could use as examples, we illustrate the interactions using a fictitious e-commerce scenario.     

A Web-Service based framework for analyzing and measuring business performance

The web services paradigm provides organizations with an environment to enhance B2B communications. The aim is to create modularized services supporting the business processes within their organization and also those external entities participating in these same business processes. Current web service frameworks do not include the functionality required for web service execution performance measurement from an organization perspective. As such, a shift to this paradigm is at the expense of the organizations performance knowledge, as this knowledge will become buried within the internal processing of the web service platform. This research introduces an approach to reclaim and improve this knowledge for the organization establishing a framework that enables the definition of web services from a performance measurement perspective, together with the logging and analysis of the enactment of web services. This framework utilizes web service concepts, DSS principles, and agent technologies, to enable feedback on the organizations performance measures through the analysis of the web services. A key benefit of this work is that the data is stored once but provides information both to the customer and the supplier of a web service, removing the need for development of internal web service performance monitoring.     

基于SOA的Web服务组合的研究

基于Web服务具有松耦合、跨平台的特性,面向服务的架构(Service-Oriented Architecture,SOA),充分利用了Web服务的松散耦合、跨平台等优势。通过将某个特定的业务流程封装为具有统一、公开接口的服务,使基于Web服务组合的业务流程集成成为可能。从而实现跨部门、跨企业的业务过程集成。主要研究基于业务流程实现服务组合的方法,应用于教材管理系统。通过业务流程执行语言(BPEL)将其以业务流程方式进行封装,而对外只暴露出统一的服务端口,从而形成粒度更大、数据共享性更好、功能内聚性更强的Web服务供外界调用,使重构后的系统业务流程有更强的灵活性和可扩展性、更加贴近系统逻辑业务流程模型。