开放网格服务体系结构OGSA及其仿真应用

该文对目前网格最新的体系结构一开放网格服务体系结构OGSA进行了介绍，该体系结构基于Web Selwices框架提出了一种网格服务结构的思想。OGSA的服务功能主要包括动态服务创建、服务发现、生命周期管理、注册和通知等。分布式仿真系统与网格有许多相似之处，同时基于HLA标准建立的分布仿真系统又存在着很多有待完善之处，所以提出将网格技术结合到仿真系统的设计中，建立基于网格的分布式仿真系统。基于OGSA的结构特点，这种新的仿真系统以建立标准的仿真服务为中心，同时实现了对仿真资源的动态分配和调度，增强了系统的可重用性和灵活性。     

网格服务实现HLA/RTI向Intemet环境的扩展

基于HLA的分布式仿真已得到广泛的应用,但组建需要跨越组织或基于公共互联网通信的基于HLA的分布式仿真应用目前还较难实现.网格计算技术在资源协调、管理方面的优势为分布式仿真提供了新的发展空间.本文在回顾基于网格技术的仿真的发展研究前沿前提下,提出了基于网格服务实现HLA/RTI向Intemet环境扩展的系统结构.系统结构在考虑融入网格技术优势之外,同时考虑到了仿真组件的可重用性、互操作性和兼容性等问题.原型系统仿真实验表明了系统结构的可行性.     

仿真网格资源自动部署设计与实现

高层体系结构(HLA)已经成为当今分布式交互仿真的标准。HLA具有良好的互操作性和可重用性,然而HLA标准中并不提供仿真资源的动态部署机制。缺乏灵活性的静态部署极大地降低了仿真系统的运行效率。设计开发了一种基于网格的分布式交互仿真平台,介绍了该仿真网格平台的体系结构,并且详细论述了该仿真网格平台下的资源自动部署处理流程。     

基于Agent体系结构的HLA联邦成员设计与实现

智能Agent建模方法是一种描述、研究复杂对象的有效手段。高层体系结构（HLA）是一种服务于复杂系统建模、仿真的技术支撑框架，为联邦成员层次上的重用和互操作提供了基础。但HLA并未对联邦成员内部仿真对象模型的重用和仿真对象的复杂性和智能性描述提供足够的支持。文章通过引入Agent体系结构提出了一种新的联邦成员设计实现方法，提高了仿真对象模型的重用性、互操作性和智能性，降低了系统耦合性。通过将RTI服务函数进行封装，简化了HLA接口凋用。     

基于XACML的网格授权服务的设计与实现

为更好地解决网格环境下分布式跨域授权问题、增强授权功能的可扩展性和可复用性,构建了基于可扩展访问控制标记语言(extensible access control markup language,XACML)规范的网格授权框架.在该框架的基础上,依照Web服务资源框架和Web服务通知规范,设计实现了基于XACML策略引擎的网格授权服务.将复杂的模块交互调用封装在授权框架内,通过简单易用的服务接口实现域间互操作时的权限分配.实现结果表明,该框架更加灵活,适用于动态、异构的网格环境.     

利用KD-FedWrapper开发可组构的联邦成员

在分布式仿真领域,HLA(High Level Architecture)使联邦成员可以作为独立的组件在特定的联邦内即插即用,极大提高了联邦成员的重用性和互操作性.但是,这种重用性和互操作性受到特定联邦约定的FOM(Federation Object Model)约束,限制了HLA倡导的重用性和互操作性思想的实现.该文采用KD-FedWrapper(联邦成员包装器)工具从可组构性思路实现联邦成员,使联邦成员具有可定制和可扩展性,使HLA倡导的重用性和互操作性思想得到充分地发挥.     

基于网格的分布式仿真综述

分布式仿真已经广泛应用于科学研究、工程、商业等方方面面.HLA的提出是为了解决分布式仿真中不同类型的仿真模型、仿真应用模块之间的互操作和提高仿真组件的重用性,并没有涉及到仿真资源层的管理,所以在面对现在分布式仿真向大规模发展和需要使用在地理位置上处于分布式的计算资源和数据资源时,存在一定的局限.基于网格的分布式仿真是一门刚刚起步的新兴技术,它致力于将传统的分布式仿真移植到网格环境中,以利用网格技术的各项优势.文中介绍了分布式仿真与网格技术的发展与应用现状,随后着重介绍基于网格的分布式仿真的研究发展前沿,并分析讨论了其面临的问题和发展的方向,为进一步的研究提供一定的指导性帮助.     

基于HLA的超联邦管理的研究与实现

本文简述了HLA架构在分布式系统设计中的重要作用，分析了HLA系统的以FOM为中心的编程模型的特点及带来的开发、维护和重用问题。本文提出的HLA中的超联邦管理方法是在联邦执行的层面上对其进行控制，实现了灵活机动的仿真方式，并成功地解决了上述问题。本文还对HLA和流行的场景渲染技术的结合做了有益的尝试，对大型可视化仿真具有一定的参考价值。     

分布式近地空间环境仿真

从近地空间环境对人类生存等的重要性方面阐述建立分布式近地空间环境仿真平台的必要性。为使其具有更好的可扩展性、可重用性以及互操作性,该文提出基于HLA的近地空间环境仿真平台联邦的基本框架,针对空间环境可能面对的主要对象,设计联邦中的主要成员。该方案可以实现联邦中各成员间的分布式集成,已应用于航天以及空间环境领域的实时仿真中。     

网格环境下基于HLA的分布交互仿真动态交互研究

基于HLA开发的分布交互仿真缺乏灵活性，不支持动态资源分配。网格服务是开发基于网络的分布交互仿真的另一途径，但只应用网格服务开发分布交互仿真，开发者必须自己创建通信机制来协调仿真执行。本文提出了一个动态交互框架，将基于HLA的分布交互仿真建立在网格服务的基础之上，来克服两者所存在的问题并发挥各自的优点，实现仿真资源的动态分配、动态状态监控及任务动态迁移。文中详细地阐述了框架的构成、框架关键服务构建的设计和实现、各种网格服务的机制及服务接口，并给出实例进行验证。     

基于BPEL4WS的网格服务组合体系结构及其分析

开放网格服务基础结构OGSI（Open Grid ServicesInfrastrstructure）把Web服务工作流引入到网格任务描述中，给出了几种Web服务与网格技术相融合机制，但并没有界定如何进行网格服务组合.而BPEL4WS（Business Process Execution Language for Web Services）是描述Web服务业务工作流的工业标准.通过对BPEL4WS和OGSI在生命周期管理、Web服务实例化和状态交互管理等方面异同的深度分析，提出了一种兼容OGIS并使用BPEL4WS来合成网格服务的高层体系结构.介绍了一个电力网电能损耗理论计算的实际应用原型系统，表明该文提出的体系结构可应用于网格服务的建模和构造.     

A collaborative platform for complex product design with an extended HLA integration architecture

How to integrate the heterogeneous, autonomous models in a distributed environment, running on Internet, integration based on multilayer federation architecture and simulation resources dynamic reuse are the major difficulties for complex product collaborative design and simulation. An extended HLA-based collaborative simulation platform for multidisciplinary collaborative design is proposed. The architecture of platform is first given. The idea and realization of four key technologies, the dynamic creation of simulation federation based on resource management federation (RMF), HLA enabled template, collaborative simulation algorithm based on stage-data synchronization and TH_RTI, an extensible HLA runtime infrastructure (RTI), which is a web enabled RTI and can be used at Internet, are emphasized. Finally, an industry case is given. The demonstration of these prototype systems shows that extended HLA integration architecture is effective infrastructure for multidisciplinary collaborative modeling and simulation (M&S).     

Synchronization in federation community networks

A large scale High Level Architecture (HLA)-based simulation can be constructed using a network of simulation federations to form a “federation community”. This effort is often for the sake of enhancing scalability, interoperability, composability and enabling information security. Synchronization mechanisms are essential to coordinate the execution of federates and event transmissions across the boundaries of interlinked federations. We have developed a generic synchronization mechanism for federation community networks with its correctness mathematically proved. The synchronization mechanism suits various types of federation community network and supports the reusability of legacy federates. It is platform-neutral and independent of federate modeling approaches. The synchronization mechanism has been evaluated in the context of the Grid-enabled federation community approach, which allows simulation users to benefit from both Grid computing technologies and the federation community approach. A series of experiments has been carried out to validate and benchmark the synchronization mechanism. The experimental results indicate that the proposed mechanism provides correct time management services to federation communities. The results also show that the mechanism exhibits encouraging performance in terms of synchronization efficiency and scalability.     

Distributed simulation of DEVS and Cell-DEVS models using the RISE middleware

With the expansion of the Web, the desire toward global cooperation in the distributed simulation technology has also been on the rise. However, since current distributed simulation interoperability methods are coupled with system implementations, they place constraints on enhancing interoperability and synchronization algorithms. To enhance simulation interoperability on the Web, we implemented the RISE (RESTful Interoperability Simulation Environment) middleware, the first existing simulation middleware to be based on RESTful Web-services (WS). RISE is a general middleware that serves as a container to hold different simulation environments without being specific to a certain environment. RISE can hold heterogeneous simulations, and it exposes them as services via the Web. One of such services is called Distributed CD++ (DCD++) simulation system, an extension of the CD++ core engine that allows executing DEVS and Cell-DEVS models. Here, we introduce a proof-of-concept design and implementation of DCD++ using the distributed simulation using the RISE environment. We show how the RESTful WS interoperability style in RISE has improved the design, implementation and the performance of the DCD++ simulator. We also discuss a substantial performance improvement of the implementation of the RISE-based DCD++ presented here, showing many advantages of the RESTful WS presented here: improved interoperability, a seamless method to be connected into a cloud computing environment, and performance improvement when compared to our SOAP-based DCD++ in a similar testing environment.     

一种分布式网格计算框架以及在大规模分子动力学模拟中的应用

分子动力学（molecular dynamics）模拟蛋白质等大分子内原子间的相互作用,蛋白质折叠所需的时间通常在微秒（10^-6s）量级，而进行模拟的时间步长在飞秒（10^-15s）量级，并且每步需要计算大量的相互作用（O（n^2），n为原子数），以致于无法模拟足够长时间的折叠过程．现今在满足精确度的需求下没有更好的模拟算法．最近，生物学家研究了一种分布式的动力学方法，使得可以利用分布在Internet上的计算机进行并行模批成为可能,本文的目标是设计并实现在分布式P2P和网格计算环境等多种异构计算资源下进行动力学模拟的可靠框架，以便更大限度地利用计算资源，加快计算过程．我们基于Java和web service技术，已经实现了对应用透明的计算框架，并已将它扩展到我们的网格计算环境,实验表明分子动力学模拟程序在该框架下运行良好．     

基于Web服务的网格体系结构及其支撑环境研究

网格技术是当前网络计算的前沿领域,基于Web服务技术构建网格系统有助于提高网格系统的可扩展性和互操作能力,是这一领域中的最新热点.但现有的工作尚未明确界定基于Web服务的网格的功能模型和实现机制.首先讨论了网格功能模型,基于OGSA(open grid service architecture)框架提出了基于Web服务的网格层次体系结构,并将Web服务工作流引入到网格任务描述中,给出一种Web服务与网格技术相融合的机制,介绍了基于Web服务的网格支撑环境WebSASE4G的总体结构和设计原理,为基于Web     

DynaGrid: A dynamic service deployment and resource migration framework for WSRF-compliant applications

Large-scale Grid is a computing environment composed of Internet-wide distributed resources shared by a number of applications. Although WSRF and Java-based hosting environment can successfully deal with the heterogeneity of resources and the diversity of applications, the current Grid systems have several limitations to support the dynamic nature of large-scale Grid.This paper proposes DynaGrid, a new framework for building large-scale Grid for WSRF-compliant applications. Compared to the existing Grid systems, DynaGrid provides three new mechanisms: dynamic service deployment, resource migration, and transparent request dispatching. Two core components, ServiceDoor and dynamic service launcher (DSL), have been implemented as WSRF-compliant Web services to realize DynaGrid, which are applicable to any Java-based WSRF hosting environment. We construct a real testbed with DynaGrid on the Globus Toolkit 4 and evaluate the effectiveness of our framework using two practical applications. The evaluation results show that dynamic service deployment and resource migration in DynaGrid bring many advantages to large-scale Grid in terms of performance and reliability with minimal overhead.     

A standards-based interoperable single sign-on framework in ARC Grid middleware

Security infrastructure is one of the most challenging tasks in the development, integration and deployment of Grid middlewares. Even though the Grid community addresses the security issue through public key infrastructures (PKI) to support mutual authentication using X.509 certificates, maintaining X.509 credentials is not that easy for non-IT-experts, and has proved to be an obstacle for a more wide deployment of Grid technologies. The identity federation is an increasingly popular technology that can facilitate cross-domain single sign-on without requiring the users to maintain any credentials additional to their own institutional accounts. We believe that utilizing identity federation for Grid middlewares is a promising path for the Grid technology to get more widely used. This paper describes a single sign-on infrastructure developed as a part of the NorduGrid ARC (Advanced Resource Connector) Grid middleware. It adopts the identity federation standard (SAML), as well as other Web Service standards. It focuses on a single sign-on solution at the middleware level for users to access Grids by only using their frequently used accounts, without being bothered to maintain X.509 credentials. Users can use their username/password only to access Grids developed in ARC middleware, as well as access Grids developed in other middlewares that requires users to provide X.509 certificates. Moreover, the single sign-on for workflow-like Grid applications (in which intermediate entities act on behalf of users) is also supported. As an important aspect of single sign-on, authorization is also considered by implementing an attribute-based authorization using SAML standard. In addition, the performance of single sign-on solution is measured. We identify performance limitations of security-related services inside this solution, and analyse the ways to avoid the limitations. To our knowledge, the work presented in this paper is the first evaluated implementation that utilizes identity federation for Grid usage on the middleware level.     

基于服务等级的网格服务质量描述语言

针对网格服务质量管理中使用服务水平协议(SLA)带来较大协商开销的问题,提出基于服务等级的网格服务质量描述语言即网格服务等级语言(CGSL)及建立在CGSL之上的网格服务质量管理框架.服务等级是轻量级SLA,提供一种区分不同服务质量的机制.CGSL基于XML技术和WSRF规范,与Web服务描述语言(WSDL)兼容,用于描述网格服务提供方所能提供的不同服务等级,为监控服务质量提供具体信息.网格服务质量管理框架建立在CGSL之上,并通过Mobile Agent监控服务质量是否得到满足.一个具体的文件存储网格服务实例用来展示CGSL在网格服务质量管理中的应用.该实例表明CGSL以少量的服务等级代替复杂的SLA,能有效降低运行时消耗,适合异构多变的网格环境.