Algorithms for checking channel passing in web service choreography

Web service choreography describes global models of service interactions among a set of participants. For an interaction to be executed, the participants must know the required channel(s) used in the interaction, otherwise the execution will get stuck. Since channels are composed dynamically, the initial channel set of each participant is often insufficient to meet the requirements. It is the responsibility of the participants to pass required channels owned (known) by one to others. Since service choreography may involve many participants and complex channel constraints, it is hard for designers to specify channel passing in a choreography exactly as required. We address the problem of checking whether a service choreography lacks channels or has redundant channels, and how to automatically generate channel passing based on interaction flows of the service choreography in the case of channel absence. Concretely, we propose a simple language Chor _c , a channel interaction sub-language for modeling the channel passing aspect of service choreography. Based on the formal operational semantics of Chor _c , the algorithms for static checking of service choreography and generating channel passing are also studied, and the complexity results of algorithms are discussed. Moreover, some illustrated service choreography examples are presented to show how to formalize and analyze service choreography with channel passing in Chor _c .     

The semantics and verification of timed service choreography

As a service composition and coordination language, the service choreography gives the global and neutral view on the collaboration among a collection of highly distributed services involving multiple different organizations or heterogeneous independent processes. In this paper, we extend the service choreography by introducing the explicit time activity, which can be used to specify and reason about the timed behaviour of Web service choreography. Then we explore an execution model for the proposed timed service choreography which possesses several novel features, such as timed activity, choreography composition, exception handling and finalization. Furthermore, a set of mapping rules is elaborately designed to translate the timed choreography into communicating sequential programs processes, thus the corresponding simulation and verification of Web services choreographies with timing restrictions can be carried out in the model checker process analysis toolkit. The case study shows that our approach is both effective and practical.     

Web应用服务器中Web Service引擎的设计与实现

Web Service为程序之间的交互提供了基础,实现了独立于程序设计语言的一致化编程模型,并以通用的方法进行应用程序集成。分析了Web应用服务器实现Web Service的关键需求,阐述了在应用服务器中基于SOAP的Web Service引擎的设计与实现,介绍了实现Web Service引擎的若干关键技术和解决办法。Web Service引擎已在自主研发的OnceAS应用服务器中实现。     

服务管理代理中Web服务的调用策略研究

服务管理代理在面向服务架构的系统中作为一个Web服务的管理中介,担负起按需动态调用Web服务的重要任务研究并实现了服务管理代理调用其所管理的Web服务的策略--响应向服务管理代理发出的Web服务请求.最后通过实现其内部的服务代理工厂利用Web服务同步调用/异步调用的机制实现对Web服务的有效动态调用.     

基于UDDI的语义Web服务发现研究

目前基于UDDI的Web服务发现机制仅提供了简单的基于关键字的搜索方法,缺乏对语义推理的支持。因此给出了一种基于UDDI的语义Web服务发现的架构,通过把Web服务的语义描述发布到UDDI注册中心,并扩展查询API的规范,在服务查找中加入语义推理,从而增强了UDDI的语义Web服务发现的能力。     

A process partitioning technique for constructing decentralized web service compositions

Web service compositions have been widely applied in different applications. A service composition is usually implemented in either a centralized or decentralized manner. Compared with the centralized service composition, the decentralized composition has no central control component, and components interact with each other directly, thereby achieving better performance. Process partitioning is a technique to divide a process into multiple parts and has been shown that it can be successfully applied to decentralizing process-driven service compositions. This paper proposes a new process partitioning technique for constructing decentralized service compositions. The proposed technique, which is based on typed digraphs and a graph transformation technique, is used for exploring available process partitioning solutions. For applications, this paper discusses the topology and interaction features about the partitioning solutions and summarizes a ranking method for them. Three experiments are conducted to evaluate the proposed methods in this paper. Experimental results show that the proposed methods can be applied in constructing decentralized service compositions effectively. In addition, the results also show that the decentralized compositions can have lower average response times and higher throughputs than the corresponding centralized compositions in the experiments.     

基于语义的Web服务发现模型研究

Web服务发现是Web服务系统架构的重要部分,现有的主流Web服务发现方法是采用基于UDDI框架的服务匹配,但由于UDDI注册中心只能提供基于关键字的查询,并且缺乏对语义信息的支持,造成服务的查准率查全率得不到保证.针对目前Web服务发现技术存在的不足,引入了语义技术,并设计了一个基于语义的服务发现原型,来验证提出的基于语义的服务发现方法的可行性.     

Semantic web service composition testbed

A huge amount of web services are deployed on the Web, nowadays. These services can be used to fulfill online requests. Requests are getting more and more complicated over time. So, there exists a lot of frequent request that cannot be fulfilled using just one web service. For using web services, composing individual services to create the added-value composite web service to fulfill the user request is necessary in most cases. Web services can be composed manually but it is a too tedious and time consuming task. The ability of automatic web service composition to create a new composite web service is one of the key enabling features for the future for the semantic web. There are some successful methods for automatic web service composition, but the lack of standard, open, and lightweight test environment makes the comparison and evaluation of these composition methods impossible. In this paper we propose an architecture for a light weight and scalable testbed to execute, test and evaluate automatic web service composition algorithms. The architecture provides mandatory components for implementing and evaluation of automatic web service composition algorithms. Also, this architecture provides some extension mechanisms to extend its default functionalities. We have also given reference implementations for web service matchmaking and composition. Also, some scenarios for testing and evaluating the testbed are given. We have found that the performance of the composition method will dramatically decrease as the number of web services increases.     

通过内容自适应改善Web服务器服务质量

在近似计算算法基础上,提出了一个最高优先级优先（Highest-Priority-First,HPF）算法。在HPF算法基础上,设计了一个Web内容自适应的PIK机制来代替传统Web服务机制,并通过修改ApacheWeb服务器软件,实现了一个基于Web内容树结构的内容自适应PIK机制。通过对PIK机制仿真实验表明,PIK机制提高了Web服务器对请求的响应质量和响应率,它为研究Web服务器区分服务和服务质量问题提供了一种新技术思路。     

基于邻接矩阵的Web服务组合

针对当前Web服务组合方法在动态性和算法时间复杂度方面存在的不足,提出一种基于邻接矩阵的服务组合方法,使用邻接矩阵表示服务间的顺序及并发关系,在构建抽象服务基础上由领域专家初步建立抽象服务的组合关系,利用Warshall算法计算传递闭包来判定服务请求是否可满足,同时构建动态服务组合流程。方法操作简单,Warshall算法时间复杂度为O(n3),在服务组合中有较好的实用性。     

Web服务个性化推荐研究综述

随着Web服务的广泛使用和互联网上服务数量的增加,如何向用户提供最佳的服务选择列表成为了新的挑战.Web服务个性化推荐实现了由被动接受用户请求向主动感知用户需求的转变.个性化的Web服务推荐方法已经成为Web服务发现和选择的有效辅助手段.Web服务的个性化推荐技术也成为了近年来服务计算领域的研究热点.对当前Web服务个性化推荐的文献进行了归类分析,总结了当前Web服务个性化推荐的技术现状、研究方法和实验的数据集,列出了未来Web服务个性化推荐研究热点和挑战.     

A measurement approach of trust relation in web service

With the advent and proliferation of web services, quality of service serves as a benchmark to differentiate and select the services. Because trust has been regarded as an essential security relationship within a distributed network environment, quality evaluation of services from the viewpoint of trust presents a significant trend in decision support for selecting service over Internet. Unfortunately, the current research in the context of web services does not accurately reflect the randomness and fuzziness of trust, the basic issue in related research about trust. In this paper, we designed two kinds of trust cloud based on cloud model theory to describe the randomness and fuzziness of trust factors. Furthermore, a formalized calculation was provided to obtain the trust degree. To our knowledge, this is the first investigation into trust of web Service considering the integration of randomness and fuzziness, and applying the cloud model to quantitative evaluation of trust in the field of web services.     

基于语义描述的Web服务工作流集成

Web服务是可以由其它软件在Internet上访问的一种软件接口。Web服务工作流则是一组按一定顺序执行的Web服务的集合。如何集成一个Web服务工作流,特别是如何运用对Web服务的语义描述来为一个工作流来自动寻找和匹配Web服务,这是目前所急需解决的问题。介绍如何用语义Web服务本体论来集成工作流,同时提出一个基于语义Web服务工作流集成的模型。     

基于用户策略的Web服务动态选择方法研究

目前的Web服务选择方法主要是服务关键词语义和属性匹配、运行性能最优评估,未能很好考虑用户对服务质量的个性化需求.对用户需求、服务质量进行模型描述,结合用户策略给出了一个服务评估和选择算法,该算法根据服务请求者的满意度对候选服务进行评估和选择.与已有的服务性能选择方法相比,该方法更能满足个性化需求.     

Dynamic web service composition based on OWL-S

Composing existing web services for enterprise applications may enable higher level of reuse. However the composition processes are mostly static and lack of support for runtime redesign. In this paper, we describe our approach to the extension of the OWL-S ontology framework for dynamic web service composition. We raise the level of abstraction and propose an abstract service layer so that web services can be com- posed at the abstract service level instead of the concrete level. Each abstract service is attached with an instance pool including all instances of the abstract service to facilitate fail-over and dynamic compositions.     

基于Web 服务和工作流的MIS框架模型的研究

分析了目前企业管理信息系统的不足,介绍了Web服务和工作流技术,提出了一种基于Web服务和工作流技术的企业管理信息系统框架,给出了系统的体系结构和软件框架模型,为建立企业管理信息系统提供了新的思路。最后给出了一具体实例,介绍了该模型的应用。     

Web Service技术在教育资源整合中的研究与实现

分析了教育资源的特点和教育资源整合中面临的问题,在深入研究Web Service技术的基础上,给出基于Web Service技术的教育资源整合系统的体系结构及实现中的关键技术,并将解决方案应用于无线接入远程教育系统,取得了良好的应用效果。     

基于Web服务的Matlab功能封装模型

为了实现对Matlab软件强大功能的跨平台调用,提出了一种基于Web服务的Matlab功能封装模型.在该模型中,根据Matlab的ActiveX自动化接口,将Matlab封装为名称为Matlab_Service的Web服务、Matlab的相应功能被封装为Matlab_Service中的相应操作,其它系统就可能通过Matlab_Service实现对Matlab功能的调用.最后,通过Matlab_Service在产品开发过程在线数据回归分析方面的应用,证明了该模型的有效性及实用性.     

基于Web Service的数值计算网格平台研究

在自强2000高性能集群计算机应用环境中使用NetSolve时,发现该系统存在一些问题。针对这些问题,结合Web Service技术提出了一种应用于高性能计算的网格系统,对该系统的体系结构进行了探讨。该系统有效地把高性能计算资源和网格技术结合在一起,取得了良好的应用效果。