基于规范流网的Web服务行为适配方法研究

Web服务适配是面向服务计算领域的重要研究内容.针对现有服务行为建模和适配技术在循环服务行为、数据流建模和状态空间爆炸方面存在的问题,提出一种新的服务行为建模和适配方法,并结合实例阐述该方法如何以规范流网为基础,建模服务行为,构造服务行为的符号化可覆盖树,构建数据依赖关系和动作依赖关系,构建符号化执行轨迹适配器,直至最后完成服务行为适配的整个建模和适配过程.     

面向MPEG-21 DIA的适配决策模型

通用多媒体内容访问是未来多媒体服务的常用模式。针对这一访问模式,MPEG-21提出了DIA技术框架,以期实现相关技术标准化。但是,DIA现在只对上下文描述等元数据制定了标准,而适配决策引擎仍然是一个开放问题。针对已有适配决策模型存在的问题,提出了一种适配决策树模型,该模型将适配决策视为序列决策,并用决策树对其建模。为满足多媒体服务的个性化需求,利用用户偏好信息建立适配决策树。此外,利用优化模型构建决策空间,使参与决策的对象数缩小为模态数,从而减少了适配决策时间,满足了多媒体服务的实时性。通过仿真实验证明,该适配决策树模型在决策误差和平均迭代次数两个指标上都优于或相近于已有的适配决策模型。     

内容适配技术研究综述

内容适配技术是实现通用多媒体接入的技术体系。MPEG-21标准提出了内容适配技术框架和服务环境描述技术规范。针对MPEG-21内容适配框架,从内容适配系统、服务环境数据交换、适配决策等方面,介绍国内外相关研究现状。     

面向SOA的企业服务总线研究与实现

针对企业日益增长的信息共享和业务整合的需求,面向SOA的企业服务总线屏蔽各类异构的应用从而实现基于SOA架构的企业应用集成是大势所趋。现有的面向SOA的企业服务总线（s-ESB）大多立足于提供Web服务容器,并没有提供统一的适配机制无缝集成各类企业应用,从而极大限制s-ESB的高可用性和可扩展性。首先,提出了一种新型的基于SOA架构的企业应用集成环境,从而明确了s-ESB在构建企业应用集成中的地位和作用;其次,提出了s-ESB的体系结构模型,并解决了协议适配,服务适配和公共服务等关键技术问题;最后,原型系统证明s-ESB的灵活性,可有效集成各类异构企业应用。     

内容适配系统设计及性能评价研究

内容适配技术是实现通用多媒体访问的主流技术,如何实现内容适配系统是内容适配技术研究中的重要问题。基于SOA架构设计并实现内容适配系统。系统具有数据管理、服务管理、内容适配和内容服务功能。采用客观和主观指标结合的评价体系,对内容适配系统的服务质量进行评价。     

面向服务的内容适配框架研究*

将面向服务的体系架构引入内容适配研究,设计了一种新颖的面向服务的适配框架,并阐述了框架的运行机制.该框架在复用性、扩展性等方面具有良好的性能.     

基于适配的服务协作流程动态管理

服务协作以服务为构造单元,通过组合不同的服务,实现复杂的业务逻辑,并以此为基础构建新的应用.为实现正确的服务协作,服务之间的交互必须是兼容且一致的.适配技术通过构造适配器来弥补服务之间的交互差异,为解决协作的一致性问题提供了有效的方法途径.然而考虑到服务计算环境的动态特性,协作适配器本身应具有动态调整及重新配置的能力,从而避免使其成为协作系统响应动态变化的可适应能力的瓶颈.文中首先给出了一种基于适配的服务协作方法,以保证服务交互的一致性.并针对提出的适配器结构,建立了适配器的执行模型,在此基础上给出了适配器的动态更新方法,使适配器具有可重配置以及动态调整的能力,从而保证了基于适配的服务协作系统的灵活性和动态可适应性.     

语义Web服务组合综述

语义Web服务的目标是,利用语义Web技术将Web服务的静态描述和动态行为与功能有机地结合起来,解决Web服务的自动发现、组合和执行等问题。语义Web服务组合是服务资源重用的一种重要方式,也是语义Web服务研究领域的一个重要内容,它以现有的语义Web服务资源为基础,通过服务组合为基于Internet的大规模复杂应用提供新的、更多的可用资源。首先对语义Web服务相关的基本概念进行归纳和总结,概述语义Web服务组合的研究内容和目标,然后根据语义Web服务组合中使用的方法学对其进行分类并分析这些方法的实现过程和特点,最后总结全文,指出下一步的研究方向。     

基于服务功能链的多域安全服务按需适配方法

传统网络的服务管理和供应模式静态僵化,难以从全局角度为跨域数据流制定统一的安全和调度策略,无法满足多样化的安全需求。提出一种基于服务功能链（SFC）的多域安全服务按需适配方法,利用软件定义网络（SDN）和网络功能虚拟化（NFV）等技术,通过多层接口建立统一的描述模型,配置所需的安全服务资源,实例化所需的安全服务功能,并使用服务功能链将安全服务功能组合,进而实现安全服务的按需适配。最后,通过搭建原型系统,在不同的实验场景中验证所提方法的可行性。     

DANCE:一种面向云-端动态集成的服务适配方法

边缘计算可以通过将计算移到边缘设备上来提高大型物联网流数据处理质量以及降低网络运行成本.对于流数据处理,边缘设备通常只有有限的计算能力和存储能力,显然不能支持所有的实时流数据查询和处理.本文尝试引入服务并在边缘和云之间灵活地划分服务来实现云-端集成,云服务和端服务之间通过事件机制进行服务适配.物联网动态环境中,云-端服务的动态适配是使云基础设施和端设备间无缝集成的关键.动态集成背景下的服务适配需要把握适配时机来应对端服务适配请求的不确定性和非完全适配等难题.针对这一问题,论文提出了一种面向云-端动态集成的服务适配方法(Dynamic Adaption cloud Services with Edge Services,DANCE).这种方法的主要贡献在于:将云服务实例和端服务实例之间的适配问题建模为二分图顶点之间的动态匹配问题,同时结合排队论中的M/M/c/∞模型对二分图最优匹配Kuhn-Munkres算法进行了优化改进,保障适配过程中端服务实例的全局平均请求响应时间最小.最后,基于真实的电能质量监控案例和数据,验证了本文方法的有效性.     

A semantical framework to engineering WSBPEL processes

Web services promise the interoperability of various applications running on heterogeneous platforms over the Internet, and are gaining more and more attention. Web service composition refers to the process of combining Web services to provide value-added services, which has received much interest in supporting enterprize application integration. Industry standards for Web Service composition, such as WSBPEL, provide the notation and additional control mechanisms for the execution of business processes in Web service collaborations. However, these standards do not provide support for checking interesting properties related to Web Service and process behavior. In an attempt to fill this gap, we describe a formalization of WSBPEL business processes, that adds communications semantics to the specifications of interacting Web services, and uses a formal logic to model their dynamic behavior, which enables their formal analysis and the inference of relevant properties of the systems being built.     

Web service adaptation: A decade’s overview

With the exponential growth of communication and information technologies, adaptation has gained a significant attention as it becomes a key feature of service-based systems, allowing them to operate and evolve in highly dynamic and uncertain environments. Although several Web service standards and frameworks have been proposed and extended, existing solutions do not provide a suitable architecture, in which all aspects of monitoring and adaptation (e.g., proactive, cross-layer, and autonomic adaptation) can be expressed. In addition, the emergence of new computing environments to host and execute various types of services (Web/cloud services, big data-intensive services, mobile services, microservices, etc.) raises the need for more efficient monitoring and adaptation systems. This survey aims to bring a synthesis and a road-map to the adaptation of service-based systems. We also discuss adaptation solutions in emerging service models, such as cloud services and big services. Based on an adaptation taxonomy which we extracted from the surveyed approaches, and by identifying the main requirements and goals of service adaptation in Web, cloud and big data environments, detailed analysis and discussions, as well as the open issues, are provided.     

Preference-driven personalization for flexible digital item adaptation

The delivery of multimedia content often needs the adaptation of the content in order to satisfy user constraints. With the Digital Item Adaptation part, the MPEG-21 standard already defines a useful frame-work to handle this task. However, in modern service-oriented architectures the functionality of adaptation is split over several services. Hence, the central instantiation of a suitable service chain needs to tackle a complex multi-objective optimization problem. In this problem between content choice and possible adaptations the current preference model in the MPEG-7/21 standard still lacks expressiveness. In the course of this paper we demonstrate this shortcoming and how the integration of more powerful models can ease the instantiation problem. Furthermore we explain how to efficiently evaluate preference trade-offs by evaluating skyline queries as currently investigated in the field of information systems. As a running example we use preference-based content adaptation in a typical media streaming application with Web services as basic modules. The contribution of our framework is to enable a central coordinator to instantiate an executable service composition chain by integrating all needed Web services to adapt the multimedia content in the best possible fashion in the sense of Pareto optimality. This work was supported in part by the German Research Foundation (DFG) within the Emmy-Noether Program of Exellence.     

一种规则驱动的网络服务组装机制

提出了一种规则驱动的服务组装方法,实现了一个基于软件Agent的框架,在运行时刻监控和管理组装流程的执行．该方法给出一个算法将流程规约转化为等价的规则集合以用于指导Agent的行为,并允许用户通过定义一组可插拔(pluggable)的自适应策略,方便地扩展流程对变化的适应能力．框架实现基于反射式中间件平台PKUAS,该平台为网络服务和软件Agent提供运行支持,并基于其反射机制为Agent提供运行时刻的环境信息．     

QoS-aware middleware for Web services composition

The paradigmatic shift from a Web of manual interactions to a Web of programmatic interactions driven by Web services is creating unprecedented opportunities for the formation of online business-to-business (B2B) collaborations. In particular, the creation of value-added services by composition of existing ones is gaining a significant momentum. Since many available Web services provide overlapping or identical functionality, albeit with different quality of service (QoS), a choice needs to be made to determine which services are to participate in a given composite service. This paper presents a middleware platform which addresses the issue of selecting Web services for the purpose of their composition in a way that maximizes user satisfaction expressed as utility functions over QoS attributes, while satisfying the constraints set by the user and by the structure of the composite service. Two selection approaches are described and compared: one based on local (task-level) selection of services and the other based on global allocation of tasks to services using integer programming.     

Content Adaptation Architectures Based on Squid Proxy Server

The overwhelming popularity of Internet and the technology advancements have determined the diffusion of many different Web-enabled devices. In such an heterogeneous client environment, efficient content adaptation and delivery services are becoming a major requirement for the new Internet service infrastructure. In this paper we describe intermediary-based architectures that provide adaptation and delivery of Web content to different user terminals. We present the design of a Squid-based prototype that carries out the adaptation of Web images and combines such a functionality with the caching of multiple versions of the same resource. We also investigate how to provide some form of cooperation among the nodes of the intermediary infrastructure, with the goal to evaluate to what extent the cooperation in discovering, adapting, and delivering Web resources can improve the user-perceived performance.     

Using ontologies and Web services for content adaptation in Ubiquitous Computing

The diversity of small mobile devices and networks enabling users to access the Internet expands every day. In this highly dynamic environment of Ubiquitous Computing, current programming paradigms do not offer the flexibility needed for software reuse. To improve this flexibility, this paper proposes the use of ontologies and Web services, within a framework of components for the content adaptation domain, to facilitate the development of software based on reuse. A case study illustrates the use of the proposed solution.     

基于服务交互行为的复杂服务协同网络建模

随着分布式计算技术的发展,以自治的服务协同与互操作为主要构造手段、结构与行为随需而变的面向服务的软件系统已成为当前主流的软件架构,分析并理解服务交互行为对于这类复杂软件系统的开发、维护和运营具有重要意义.针对面向服务的软件系统中基本构成元素Web服务的复杂交互执行行为,考虑到服务自治性及系统规模化所带来的复杂性,借鉴复杂网络建模分析方法,提出了一种考虑服务行为特征的服务动态行为生长演化模型.模型首先以真实服务的服务结构数据为基础,以服务间参数关联关系为核心,通过参数匹配建立服务结构网络作为基本连通性约束,代表可能发生交互关系的服务.然后,基于服务间的择优选择、组合交互及动态重组等特性,对面向服务的软件系统生长演化及动态执行行为进行了仿真建模.在Seekda及QWS数据集上进行了仿真实验,结果表明:与传统的软件系统的层次性结构有所不同,由自治的Web服务所构成的软件系统具有更强的模块性;与系统中个体服务演化规则,如择优连接及动态重组相比,服务结构网络的性质对系统最终形态有更重要的影响,相关结果对大规模服务软件的构建及分析具有重要的指导意义.