服务社区的无标度性质研究

文章揭示了基于UDDI注册中心的增长性服务社区网络社团结构性质,并从服务注册拓扑结构来研究与总结服务社区网络的无标度性质。因此本文关于无标度服务社区网络的研究为面向服务的体系结构提供有力的理论与实践依据,也对复杂网络的理论与实证研究起到了一定的推动作用。     

基于UDDI的Web服务发现研究

基于UDDI的Web服务发现机制仅提供了基于语法层关键字的匹配方法,缺乏语义推理的支持.在相关研究的基础之上,提出了一个基于UDDI的Web服务注册/发现方法,使得服务提供者可以发布OWL-S语言描述的服务,并发布到UDDI注册中心.在传统UDDI注册中心之外新建一层Sem-UDDI注册中心,使用Sem-UDDI注册中心来存储服务的语义信息和服务相关的分类属性,并由服务匹配引擎计算服务属性之间的语义相似度,从而支持基于语义的推理查询,增强了UDDI的语义Web服务发现的能力.     

点强度优先的UDDI超级节点部署策略

服务注册中心(UDDI)是SOA的重要组成部分,为解决UDDI存在的单点故障和扩展性等问题,人们提出了附属服务注册中心和P2P等解决方法,但实际效果较差.现采用"在密集区域投放服务点"的思路,提出一种具有超级节点的语义路由UDDI模型SPSR-UDDI,模型依据点强度优先连接原则,动态调整节点间的部分连接关系,使得全局服务响应时间较短;通过建立网络演化模型,实现了网络自组织演化过程,仿真实验验证了其有效性.     

UDDI分类机制的研究与应用

UDDI协议是面向服务体系结构协议栈中的重要成员,并且已经成为发布标准或规范及遵循这些标准或规范的应用服务的一个统一描述、发现与集成的工具。在介绍UDDI协议数据模型基础上,深入分析UDDI注册中心的标识法与分类法的实现机制,并结合应用实验服务分类标识方法,描述了UDDI注册中心中的标识法及分类法的设计与实现过程。     

基于UDDI的cnXML注册中心的设计与实现

随着网络的发展,电子商务已经成为企业的重要贸易手段.在电子商务系统中,注册中心是企业发布自身服务、查找电子商务贸易伙伴、获取商务信息的主要途径.根据cnXML注册规范,结合现有的UDDI技术,该文在cnXML注册规范基础上设计并实现了一个基于UDDI的cnXML注册中心--UCR,它采用了3层设计方案,主要实现了注册服务、安全访问控制和系统服务功能.     

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。     

利用经济模型架构QoS-Aware的eUDDI

QoS(QualityofService)问题是网络服务(WebServices)在实际应用中的一个关键问题,文章提出了一个QoS-Aware的eUDDI的架构设计,使用增强的UDDI(enhancedUDDI),在传统UDDI注册中心中增加了服务质量确认机制,并且基于经济模型提供了一个自动化的网络交易平台来提高网络服务的效率和质量。该交易平台是UDDI注册中心扩展的一部分,可根据不同的经济模型和交易策略由Web服务的提供者和使用者双方进行定制。     

基于本体相似的Web服务搜索

随着越来越多的Web服务被提交到UDDI注册中心注册,搜索一个合适的Web服务开始变得和在互联网上找到一个合适的页面同样困难。现有的技术主要是通过关键字匹配的技术来对UDDI注册中心Web服务的描述信息进行检索。但鉴于Web服务描述信息非常稀疏的特点,传统的信息检索技术并不能得到很好的效果,因此提出了基于本体的Web服务检索技术。在已有的对Web服务检索流程的改进的基础上,充分利用了从UDDI注册中心得到的Web服务描述信息,用本体来描述其内部的关系,并在此基础上应用本体相似技术来比较和匹配Web服务描述信息。     

Decentralising a service-oriented architecture

Service-oriented computing is becoming an increasingly popular paradigm for modelling and building distributed systems in open and heterogeneous environments. However, proposed service-oriented architectures are typically based on centralised components, such as service registries or service brokers, that introduce reliability, management, and performance issues. This paper describes an approach to fully decentralise a service-oriented architecture using a self-organising peer-to-peer network maintained by service providers and consumers. The design is based on a gradient peer-to-peer topology, which allows the system to replicate a service registry using a limited number of the most stable and best performing peers. The paper evaluates the proposed approach through extensive simulation experiments and shows that the decentralised registry and the underlying peer-to-peer infrastructure scale to a large number of peers and can successfully manage high peer churn rates.     

基于SOA总线的资源协同组织机制

面向服务架构(SOA)是一种架构模型和开发概念,对总线的资源组织方式进行设计。通过总线资源的协同组织机制,实现总线上服务的动态加入和退出机制、服务状态动态变化机制、负载感知的自适应机制和节点的容错机制。在仿真与开发中,证实了该机制效率高、收敛快、适应性好,适用于大型分布式应用集成系统。     

A platform for P2P agent-based collaborative applications

The operational environment can be a valuable source of information about the behavior of software applications and their usage context. Although a single instance of an application has limited evidence of the range of the possible behaviors and situations that might be experienced in the field, the collective knowledge composed by the evidence gathered by the many instances of a same application running in several diverse user environments (eg, a browser) might be an invaluable source of information. This information can be exploited by applications able to autonomously analyze how they behave in the field and adjust their behavior accordingly. Augmenting applications with the capability to collaborate and directly share information about their behavior is challenging because it requires the definition of a fully decentralized and dependable networked infrastructure whose nodes are the user machines. The nodes of the infrastructure must be collaborative, to share information, and autonomous, to exploit the available information to change their behavior, for instance, to better accommodate the needs of the users to prevent known problems. This paper describes the initial results that we obtained with the design and the development of an infrastructure that can enable the execution of collaborative scenarios in a fully decentralized way. Our idea is to combine the agent-based paradigm, which is well suited to design collaborative and autonomous nodes, and the peer-to-peer paradigm, which is well suited to design distributed and dynamic network infrastructures. To demonstrate our idea, we augmented the popular JADE agent-based platform with a software layer that supports both the creation of a fully decentralized peer-to-peer network of JADE platforms and the execution of services within that network, thus enabling JADE multiagent systems (MASs) to behave as peer-to-peer networks. The resulting platform can be used to study the design of collaborative applications running in the field.     

METEOR-S WSDI: A Scalable P2P Infrastructure of Registries for Semantic Publication and Discovery of Web Services

Web services are the new paradigm for distributed computing. They have much to offer towards interoperability of applications and integration of large scale distributed systems. To make Web services accessible to users, service providers use Web service registries to publish them. Current infrastructure of registries requires replication of all Web service publications in all Universal Business Registries. Large growth in number of Web services as well as the growth in the number of registries would make this replication impractical. In addition, the current Web service discovery mechanism is inefficient, as it does not support discovery based on the capabilities of the services, leading to a lot of irrelevant matches. Semantic discovery or matching of services is a promising approach to address this challenge. In this paper, we present a scalable, high performance environment for Web service publication and discovery among multiple registries. This work uses an ontology-based approach to organize registries into domains, enabling domain based classification of all Web services. Each of these registries supports semantic publication and discovery of Web services. We believe that the semantic approach suggested in this paper will significantly improve Web service publication and discovery involving a large number of registries. This paper describes the implementation and architecture of the METEOR-S Web Service Discovery Infrastructure, which leverages peer-to-peer computing as a scalable solution.     

结构化P2P覆盖网络中匿名通信的研究

结构化P2P覆盖网络提供一个自组织、可升级且容错性能好的合作P2P应用平台.借助于结构化覆盖网络的自组织和结构化特性,本文在结构化P2P覆盖网络基础上提出了一种不需要中心管理节点的重路由匿名通信机制.由于覆盖网络的开放性,本文分析了重路由路径长度的期望值与转发概率的关系以及重路由路径长度的期望值与覆盖网络中恶意成员数量的关系,并且分析了随着重路由路径重组轮数的增加,恶意节点将以更高的概率找到发起者.计算数据表明,采用递减转发概率将使得重路由路径长度的期望值显著降低,因而能保证良好的通信延时.     

A negotiation framework for content distribution in mobile transient networks

Transient networks are spontaneous networks that appear for a short period of time in order to provide basic services such as connectivity and content distribution among a small community. Nowadays mobile devices are becoming multimode by nature providing multiple connection paths. This paper investigates the efficiency and benefit of a mobile transient network where multiple nodes collaborate, offering a multihomed network with community services by means of intelligent agents. The paper concretely proposes an architecture able to fully support a peer-to-peer transient community during both negotiation and service steps for two different modes: file download and multimedia streaming. The first mode, implemented on intelligent and cooperative agents, provides two negotiation models (fair and dynamic) in order to guarantee wider flexibility for different possible scenarios and community models; the second one implements a content delivery system into transient community, taking advantage of multihomed features of mobile devices.     

基于P2P网格的视频点播自适应性研究

研究了基于P2P网格的网络自适应视频点播的可行性及有效性．在提出的GridVOD系统中，点播用户在享受服务的同时也能够作为mini-server向他人提供服务，系统在利用P2P获得良好的可扩展性的同时，基于网格的安全策略为系统管理提供了保障．GridVOD将具有相似兴趣的关联结点组织在对等结点自治组中，利用基于网格环境的系统监测服务进行网络自适应视频组播，并且利用分布式协同缓存来增强本地服务能力．分析表明，网络自适应视频点播机制提高了系统的服务质量．     

Cooperative Media Data Streaming with Scalable Video Coding

Live peer-to-peer (P2P) streaming has become a promising approach for broadcasting non-interactive media content from a server to a large number of interested clients. However, it still faces many challenges such as high churn rate of peer clients, uplink bandwidth constraints of participating peers, and heterogeneity of client throuput capacities. This paper presents a new P2P network called LSONet, a collaborative peer-to-peer streaming framework for scalable layer-encoded bit streams. The contributions are the combination of the advantages of both layered conding and mesh-based packet exchange. With layered coding, it overcomes overlay bandwidth limitatioins and heterogeneity of client capacities. With mesh based overlay streaming, it can better handle peer churns, as compared to tree-based solutions. For achieving these targets, this paper employs a gossip-based data-driven scheme for partnership formation, and proposes two algorithms, optimized transmission policy (OTP) and graceful degradation scheme (GDS), for multi-layers allocation. The proposed system is completely self-organizing, and in a fully distributed fashion. Extensive simulations show that LSONet achieves higher quality of service by peer-assisted streaming and layered video coding. Also, through comparison, results show that the system outperforms some previous schemes in resource utilization and is more robust and resilient for nodes departure, which demonstrate that it is well-suited for quality adaptive live streaming applications.     

Service oriented architectures: approaches,technologies and research issues

Service-oriented architectures (SOA) is an emerging approach that addresses the requirements of loosely coupled, standards-based, and protocol- independent distributed computing. Typically business operations running in an SOA comprise a number of invocations of these different components, often in an event-driven or asynchronous fashion that reflects the underlying business process needs. To build an SOA a highly distributable communications and integration backbone is required. This functionality is provided by the Enterprise Service Bus (ESB) that is an integration platform that utilizes Web services standards to support a wide variety of communications patterns over multiple transport protocols and deliver value-added capabilities for SOA applications. This paper reviews technologies and approaches that unify the principles and concepts of SOA with those of event-based programing. The paper also focuses on the ESB and describes a range of functions that are designed to offer a manageable, standards-based SOA backbone that extends middleware functionality throughout by connecting heterogeneous components and systems and offers integration services. Finally, the paper proposes an approach to extend the conventional SOA to cater for essential ESB requirements that include capabilities such as service orchestration, “intelligent” routing, provisioning, integrity and security of message as well as service management. The layers in this extended SOA, in short xSOA, are used to classify research issues and current research activities.     

Distributed distance measurement for large-scale networks

There is an increasing trend in the Internet that a set of replicated providers are qualified for a service or resource request from a client. In this case, it is advantageous to select the best provider considering some distance measures, such as hop count or path latency. In this paper, we present a group-based distance measurement service (GDMS), which estimates and disseminates distance information of node-pairs in large-scale wide area networks. GDMS is fully distributed and does not rely on any centralized servers; thus is particularly suitable for the rapidly popularized peer-to-peer applications. The key concept in GDMS is measurement groups (MGroups). Nodes are self-organized into MGroups to form a hierarchical structure. A set of algorithms are proposed to handle network dynamics and optimize the group organization to reduce system costs as well as improve estimation accuracy. Moreover, a novel multicast-based algorithm is used for both intra- and inter-group performance measurements. Performance evaluation over different network topologies shows that GDMS is scalable and provides effective distance information to upper-layer applications at a relatively low cost.