基于非确定性推理的网构软件服务质量动态评估方法

提出了网构软件环境下一种基于非确定性推理的构件服务质量动态评估方法.该方法基于贝叶斯网络,其主要特点在于考虑了用户对构件的QoS需求,可以预测在用户多种QoS需求下采用分级策略的构件服务能力,支持评估模型的动态更新,提高了评估结果的准确性.在自主开发的服务协同总线(Once-SCB)平台上进行了应用与验证,结果表明,该评估模型准确、有效,可以在用户多种QoS需求下为其选择最为合适的构件.     

实时嵌入式环境中面向构件系统的QoS模型研究

将基于构件技术的开发引入到实时嵌入式软件平台能够很好地适应嵌入式领域多样性的特点,满足对软件开发效率和软件质量的要求。为保证实时嵌入式环境对资源动态变化的需求，考虑到系统资源的全局管理特性，仅从应用中增加QoS适应机制是不够的，还需在现有的构件框架中增加QoS管理机制。为此，提出了一种面向CCM构件系统的QoS模型，能够主动适应动态变化的资源状态，模型中层次式的QoS转换器的设计简化了用户对服务的QoS参数配置。     

基于CCM的构件组装技术的研究与应用

随着计算机网络技术的应用发展,分布式构件技术成为分布式计算领域的热点,CCM就是主流的分布式构件技术之一.分析了CORBA构件模型(CCM)的特点:即通过端口定义构件对外提供的功能、通过端口定义构件所需要的外部功能,构件通过端口进行组装.在产品生命周期管理(PLM)中的供应链管理系统(SCM)中充分应用了0EM及其端口组装方法,实现在分布式环境下软件构件的即插即用功能,使SCM系统具有良好的可移植性和平台无关性.     

基于CCM的软件构件组装技术的研究

OMG在推出的CORBA3．0规范中提出了一个构件模型（CCM）。CORBA构件不仅定义了对外提供的功能,而且还定义了构件所需要的外部功能,使得构件可以利用接口进行组装。同时CCM借鉴了EJB、COM等构件模型的优点,并充分利用了CORBA的开放性。本文在对CORBA构件模型以及模型组装框架中的相关技术进行研究的基础上,努力探索基于CCM的构件组装在系统开发中的应用。     

高速网络多媒体传输中自适应QoS保证问题

1.引言自适应QoS技术是随着Internet中多媒体应用需求的不断增加和网络资源的限制而提出和不断发展的。何谓自适应QoS?它可定义为:“在网络资源有限的条件下,以最小的代价,在网络状态变化时,能最大限度满足用户对网络资源的需求,并获得最优的服务质量保证。”自适应QoS包括多媒体音/视频流的QoS保证、无线网络QoS保证、自适应路由、Inter-net代理服务器缓冲自适应等多个方面。国内外提出了众多自适应QoS的理论和模型,如文[1]设计了基于计算机微环境的CPU、网络接口的动态QoS管理模型AQUA,提出了集成一体化QoS管理的思想;文[2]开发了一种综合QoS管理模型,在端系统和网络中提供端到端的全程QoS保证;文[3]是RSVP的设计者LiXia Zhang提出的基于DiffServ模型的分层QoS管理模型,将自适应QoS的思想引入IP QoS领域。我们认为,总体来说当前的研究成果大都只涉及到静态的QoS调整,而QoS自适应应当集中考虑动态的资源变动方案,同时,应当在适应策略上适当考虑多种因素,如优先级、丢失率、媒体特性等。本文论述自适应QoS策略的产生和发展     

一种用于软件通信体系结构的构件模型

软件通信体系结构(SoftwareCommunicationsArchitecture,简称SCA)已被软件无线电(SoftwareDefinedRadio,简称SDR)论坛采纳为嵌入式系统的标准通信软件结构。SCA提供了一种支持通信软件和硬件可移植、可配置、可扩充和可重用的软件平台,但作为构件框架时仍显不足,主要是缺乏明确的构件模型。在研究CORBA构件模型(CORBAComponentModel,简称CCM)基础上,提出了适用于SCA的轻量级(Lightweight,简称Lw)CORBA构件模型———LwCCM。     

基于CCM的网络信息安全构件的设计与实现

信息安全,特别是网络环境中所传输信息的安全性,已经成为影响网络进一步发展的重要因素。信息安全构件是为了在分布式网络应用环境中,提供网络安全技术而提出的。本文首先介绍了CCM规范实现的CCM构件平台,遵循CORBA构件模型CCM1.0,在符合CORBA2.3规范的StarBus分布计算平台上开发了服务器端信息安全构件原型。同时,介绍了一种捕获网络数据包的方法。采用成熟的CCM构件技术和安全技术,提供一个分布式网络安全管理平台。     

基于CCM的构件组装技术的研究与应用

随着计算机网络技术的应用发展,分布式构件技术成为分布式计算领域的热点,CCM就是主流的分布式构件技术之一。分析了CORBA构件模型（CCM）的特点：即通过端口定义构件对外提供的功能、通过端口定义构件所需要的外部功能,构件通过端口进行组装。在产品生命周期管理（PLM）中的供应链管理系统（SCM）中充分应用了CCM及其端口组装方法,实现在分布式环境下软件构件的即插即用功能,使SCM系统具有良好的可移植性和平台无关性。     

CORBA构件模型研究与实现

对几种构件模型进行了比较分析，研究了CORBA构件模型体系结构，提出了CCM构件平台实现技术及方法，并给出了采用国防科大计算机学院研制的CCM构件平台进行程序开发的步骤，体现出CORBA构件模型可以简化CORBA服务器方的应用开发过程，并能够提高CORBA的易用性。     

无线网络构件化协议研究

层次化网络体系结构设计本身存在缺陷,如冗余、各层之间无交互等.由于这些缺陷,在应用过程中会遇到诸多问题,如QoS保障、网络安全等,层次化网络体系结构运用于无线网络除了会遇到上述问题外,还面临资源不足、间歇链路等限制.为消除层次网络设计缺陷,解决应用中的问题和限制,提出了构件化网络体系结构.构件化网络体系结构打破当前网络层次化概念,将网络按照功能协议进行划分,形成低耦合功能构件.通过组合各构件向应用数据提供高质量服务.对构件化协议体系进行详细设计.     

Model driven middleware: A new paradigm for developing distributed real-time and embedded systems

Distributed real-time and embedded (DRE) systems have become critical in domains such as avionics (e.g., flight mission computers), telecommunications (e.g., wireless phone services), tele-medicine (e.g., robotic surgery), and defense applications (e.g., total ship computing environments). These types of system are increasingly interconnected via wireless and wireline networks to form systems of systems. A challenging requirement for these DRE systems involves supporting a diverse set of quality of service (QoS) properties, such as predictable latency/jitter, throughput guarantees, scalability, 24x7 availability, dependability, and security that must be satisfied simultaneously in real-time. Although increasing portions of DRE systems are based on QoS-enabled commercial-off-the-shelf (COTS) hardware and software components, the complexity of managing long lifecycles (often ∼15-30 years) remains a key challenge for DRE developers and system integrators. For example, substantial time and effort is spent retrofitting DRE applications when the underlying COTS technology infrastructure changes.This paper provides two contributions that help improve the development, validation, and integration of DRE systems throughout their lifecycles. First, we illustrate the challenges in creating and deploying QoS-enabled component middleware-based DRE applications and describe our approach to resolving these challenges based on a new software paradigm called Model Driven Middleware (MDM), which combines model-based software development techniques with QoS-enabled component middleware to address key challenges faced by developers of DRE systems — particularly composition, integration, and assured QoS for end-to-end operations. Second, we describe the structure and functionality of CoSMIC (Component Synthesis using Model Integrated Computing), which is an MDM toolsuite that addresses key DRE application and middleware lifecycle challenges, including partitioning the components to use distributed resources effectively, validating software configurations, assuring multiple simultaneous QoS properties in real-time, and safeguarding against rapidly changing technology.     

AGENT ENABLED ADAPTIVE MANAGEMENT OF QoS ASSURED PROVISION OF COMPOSITE SERVICES

The assurance of quality-of-service (QoS) is critical for the successful deployment of service-oriented applications, especially in open, dynamic, and distributed cross-organizational environments. Adaptive management of the QoS assured provision of composite services is required for more reliable, fault-tolerant, and flexible service delivery in such environments. It can be realized with software agents offering a unified framework and necessary capabilities for carrying out different adaptive management tasks across the whole lifecycle of composite service provision.     

CCMPerf: A Benchmarking Tool for CORBA Component Model Implementations

Commercial off-the-shelf (COTS) middleware is now widely used to develop distributed real-time and embedded (DRE) systems. DRE systems are themselves increasingly combined to form systems of systems that have diverse quality of service (QoS) requirements. Earlier generations of COTS middleware, such as Object Request Brokers (ORBs) based on the CORBA 2.x standard, did not facilitate the separation of QoS policies from application functionality, which made it hard to configure and validate complex DRE applications. The new generation of component middleware, such as the CORBA Component Model (CCM) based on the CORBA 3.0 standard, addresses the limitations of earlier generation middleware by establishing standards for implementing, packaging, assembling, and deploying component implementations.There has been little systematic empirical study of the performance characteristics of component middleware implementations in the context of DRE systems. This paper therefore provides four contributions to the study of CCM for DRE systems. First, we describe the challenges involved in benchmarking different CCM implementations. Second, we describe key criteria for comparing different CCM implementations using key black-box and white-box metrics. Third, we describe the design of our CCMPerf benchmarking suite to illustrate test categories that evaluate aspects of CCM implementation to determine their suitability for the DRE domain. Fourth, we use CCMPerf to benchmark CIAO implementation of CCM and analyze the results. These results show that the CIAO implementation based on the more sophisticated CORBA 3.0 standard has comparable DRE performance to that of the TAO implementation based on the earlier CORBA 2.x standard.Arvind S. Krishna is a PhD student in the Electrical Engineering and Computer Science Department at Vanderbilt University and a member of the Institute for Software Integrated Systems. He received his MA in management from the Brila Institute for Technology and Science (BITS), Pilani, India and his MS in computer science from University of California, Irvine. His research interests include patterns, real-time Java technologies for Real-Time Corba, model-integrated QA techniques, and tools for partial evaluation and specialization of middleware. He is a student member of the IEEE and ACM. Contact him at the Inst. for Software Integrated Systems, 2015 Terrace Pl., Nashville, TN 37203.Balachandran Natarajan is a senior staff engineer at the Institute for Software Integrated Systems and a PhD student in electrical engineering and computer science at Vanderbilt University. His research focuses on applying patterns, optimization principles, and frameworks to build high-performance, dependable, and real-time distributed systems. He received his MS in computer science from Washington University. Contact him at the Inst. for Software Integrated Systems, 2015 Terrace Pl., Nashville, TN 37203.Aniruddha Gokhale is an assistant professor in the Electrical Engineering and Computer Science Department at Vanderbilt University and a senior research scientist at the Institute for Software Integrated Systems. His research focuses on real-time component middleware optimizations, distributed systems and networks, model-driven software synthesis applied to component middleware-based distributed systems, and distributed resource management. He received his PhD in computer science from Washington University. Contact him at the Inst. for Software Integrated Systems, 2015 Terrace Pl., Nashville, TN 37203.Douglas C. Schmidt is a professor in the Electrical Engineering and Computer Science Department at Vanderbilt University and a senior research scientist at the Institute for Software Integrated Systems. His research interests include patterns, optimization techniques, and empirical analyses of software frameworks and domain-specific modeling environments that facilitate the development of distributed real-time and embedded middleware and applications running over high-speed networks and embedded system interconnects. He received his PhD in information and computer science at the University of California, Irvine. Contact him at the Inst. for Software Integrated Systems, 2015 Terrace Pl., Nashville, TN 37203.Nanbor Wang is a Research Scientist in the Distributed Technologies Group at the Tech-X Corporation in Boulder, Colorado. He received M.S. and Ph.D. degrees in Computer Science from Washington University in St. Louis, Missouri. While working for his degree, he also worked as a Research Associate in the Center of Distributed Object Computing in the Department of Computer Science where he conducted research on design, implementation and analysis of object-oriented and component-based techniques for development of distributed systems and management of extra-functional concerns. Dr. Wangs work currently focuses on developing and applying middleware techniques, such as CORBA and Grid Computing, for enabling distributed and parallel scientific applications, such as, distributed data analysis, remote visualization and collaboration, and, work-flow management for large-scale scientific applications.Gautam H. Thaker was born in Amdavad, India, in 1955. He holds a BSEE (75) and MSEE (77) from Clemson University, Clemson, SC. He spent the 85-86 academic year at M.I.T. as a visiting researcher. His research interests include analysis, design, construction and validation of real-time, command and control systems. In particular he has focused on interactions between operating systems, networking protocols, and middleware technologies.     

Ad Hoc网络中基于DSR的QoS路由协议研究

AdHoc网络的特性决定为各种多媒体业务的服务质量提供保证是很难解决的问题。AdHoc网络路由协议的QoS研究正是试图解决这样的问题。本文介绍了DSR路由协议和AdHoc网络QoS路由技术的相关概念。然后,对基于DSR的QoS实现的路由协议进行了详细的分析。最后探讨了其今后的发展动态和研究方向。     

Web QoS及其保证方法

Internet的服务模式正由传统的数据通信与信息浏览向电子交易与服务转变,仅靠网络QoS机制并不能完全解决端到端的QoS控制问题。Web服务器系统作为核心设施,必须同样具备建立和支持QoS的机制与策略,对不同的用户或HTTP请求提供区分服务和性能保证。文中综述了Web QoS的发展情况、研究现状以及保证方法(包括请求分类机制的划分方法、Web服务供应商的Web系统解决方案以及无线网络的保证方法),并分析了进一步的研究方向。     

认知无线电网络动态QoS保证机制研究

针对认知无线电网络提出了一种基于中间件的分布式动态QoS保证机制DQAM,当网络对应用承诺的QoS保证发生变化,或者应用对网络的QoS要求发生变化时,通过网络和应用之间的反馈和协商,在分析当前网络状态和应用需求的基础上,根据特定的策略对网络和应用进行动态干预,在保证一定QoS的前提下,使应用最大程度的适应网络,网络最大限度的支持应用,以提高认知无线电网络对应用的支持能力和应用对网络的适应能力。对DQAM的原理、系统组成以及运行方式等,进行了讨论;从体系结构、工作过程、信息收集与策略生成和节点（任务）重构等4个方面,给出了DQAM的基本框架,并通过一个典型场景就DQAM的应用问题进行了探讨。     

Web QoS控制研究综述

Internet的服务模式正由传统的数据通信与信息浏览向电子交易与服务转变 ,Web服务器系统作为支持电子商务的核心设施 ,需要对不同的用户或HTTP请求提供区分服务和性能保证 ,因此必须具备建立和支持服务质量 (QualityofService ,QoS)控制的机制与策略 .该文综述了WebQoS控制的研究现状 ,包括Web请求的分类机制、Web服务器应用软件的QoS控制机制、操作系统的WebQoS控制机制、中间件的WebQoS控制机制以及Web服务器集群系统的QoS控制机制与策略 ,并分析了进一步的研究方向 .     

支持组合服务QoS动态优化的服务总线

面向服务的体系结构SOA已经逐渐成为应用软件系统集成的主流技术。服务总线在构建SOA基础架构中起着关键作用,如何根据服务QoS进行动态优化是服务总线中的重要研究课题之一。SOARBus是一个支持QoS动态优化的服务总线,SOARBus实现组合服务请求动态调度算法和QoS感知的组合服务动态调整算法,使其能够根据引擎负载按照负载均衡原则对组合服务请求进行动态调度和以及在组合服务执行期间根据QoS对组合服务进行动态调整。