基于网格的WebService实现

Web Service提供了在不同体系结构下构建的网站之间相互提供应用接口服务、数据的一种仿案。它是网格服务的基础,这里讨论了网格计算和WS的基本概念,通过实现的一个应用描述了构建基于GT的带有安全性的WS的方法。     

基于软件代理的网格信息服务

计算网格允许对地理域上分散的资源进行大范围的、深入的、一致的共享。它们的固有属性将发现处于不同行政区域的资源和预测资源的性能并监控其行为的事务进行合并。监控和发现服务MDS（Monitoring and Discovery Service）是Globus工具集提供的一项主要服务,它可以用于为已存在的基于代理的资源发布和发现系统提供网格信息服务。给出一个代理系统,它使用MDS中的网格信息协议GRIP（Grid Information Protocol）和网格注册协议GRRP（Grid Registration Protocol）去发现虚拟组织并监控相关资源,使得此系统具有资源代理、监控及性能预测的作用。     

基于WebService的网格服务功能的研究

Web Service分为无状态的和有状态的两种,网格服务实例中有些也是特殊的有状态的Web服务实例,而直接开发网格服务的难度较大,因此可以开发特殊的有状态的Web Service实例来增加网格服务的功能.介绍了Web Service的相关知识,开发了两个Web Service服务实例并部署到tomcat中,同时在GT4环境下部署网格服务,并用MathService服务实例测试部署情况;将两个Web Service服务实例部署到网格服务的容器中,并编写客户端程序测试服务的运行情况,观察结果说明可以通过开发特殊的Web Service服务实例来增加网格服务的功能.     

一种轻量级的Web服务QoS预测机制

服务质量（Quality of Service, QoS）作为Web服务非功能属性的代表,已被广泛作为重要的服务选择依据。然而现有QoS预测方法存在着难以兼顾运行效率与预测准确度的问题,且普遍忽略了服务器端的QoS预测。针对该问题,提出一种适用于服务器端环境的轻量级QoS预测机制（LPM）。LPM基于卡尔曼滤波算法构建QoS状态转换模型实现来QoS预测,并借助预测准确度优化预测周期。实验结果显示,在存在显著量测噪声的应用环境中,LPM的预测准确度明显优于常规方法。LPM的QoS预测结果可为用户选择Web服务提供首要的客观依据。     

基于资源预测的网格任务调度模型

跨越虚拟组织中多个域(或集群)的网格任务调度由于资源的不确定性（如动态性和异构性）而成为网格应用中亟待解决的问题。提出了一种有效的基于资源预测的网格任务调度模型——RPTS,该模型利用加权最小二乘方法进行参数估计的自回归滑动平均(ARMA)预测方法对网格环境下的主机负载进行预测。利用上述资源预测结果和一类数据并行性网格任务的建模结果,对它们进行预处理、匹配并调度执行。RPTS充分考虑了网格环境下资源的动态性和异构性,为解决网格环境下任务调度问题提供了一种较好的方法。与其他一些网格任务调度方法进行了一系列的仿真实验,结果表明RPTS模型具有任务执行时间最短和稳定性较好的特点。     

一个科学计算服务网格应用系统的设计与实现

为扩大计算能力的共享规模，并充分复用已有的计算程序．提出了一个SCS服务的概念．一个SCS服务把一个科学计算程序和它的宿主环境（计算节点）结合起来，构成了一个提供科学计算服务的基本单元．设计了一个网格应用系统（PCG系统）来管理SCS服务．PCG系统是一个3层的架构，顶部是一个Web门户，中间是SCS服务管理器，网格中间件系统位于后端．SCS服务管理器是整个系统的核心部分，包含了四个模块：通讯模块（comm）、需求转换模块（User Requirements Translator）、服务信息查询协商模块（Service Query＆Broker）和服务提交管理模块（Service Handler）．基于GlobusToolkit作为中间件，PCG系统已经在北京大学校园网内跨越多个局域网进行了实现．在PCG系统上．已经成功地运行了若干个实际科学计算的实例．     

教育培训行业PaaS解决方案

PaaS（Platform-as-a—Service：平台即服务）是把服务器平台作为一种服务提供的商业模式。通过网络进行程序提供的服务称之为SaaS（Software as a Service）,而云计算时代相应的服务器平台或者开发环境作为服务进行提供就成为了PaaS（Platform as a Service）。PaaS也是SaaS模式的一种应用。但是,PaaS的出现可以加快SaaS的发展,     

网格服务及调用模型研究

开放网格服务体系结构（OGSA）是在Globus网格计算工具包和Web Service技术融合的基础上提出的一套规范和标准.OGSA以服务为中心,将一切都抽象为服务,网格服务是OGSA的基本概念.在介绍了网格服务的思想之后,分析了OGSA的架构体系,讨论了网格服务的组成以及典型标准接口的功能描述,研究了创建网格服务实例的过程,提出了一个网格服务调用模型,并对其处理过程进行了描述.     

用MyProxy改进统一认证服务CAS的网格门户研究

分析了统一认证服务CAS（Central Authentication Service）作为网格门户单点登录系统的不足，阐述了MyProxy（在线证书仓库）的工作原理，并给出了将两者相结合实现网格门户的方案。最后说明了该方案在实现单点登录（SSO）和网格门户中的安全性和健壮性。     

基于网格的虚拟数据源的设计与实现

随着商业和科学研究领域中数据密集型应用越来越广泛,提供透明地访问分布式的、异构的数据源将成为这种应用的关键。提出一种基于网格数据仲裁服务（Grid Data Mediation Service,GDMS）的数据集成系统,它能够把网格中的分布式的、异构的数据源表示成一个逻辑上虚拟的数据源,并设计出了一种灵活的映射模式来描述构建虚拟数据源的过程。     

基于Web服务的分布式仿真资源重用

实现全球资源共享是以网格为代表的新一代信息技术的主要目标,然而现有的分布式仿真资源远没有实现全球范围的共享,原因是缺乏对仿真资源统一的组织和管理,资源的可重用性不强,而利用网格和Web服务有望解决该问题.该文分析了Web服务、网格计算和高层体系结构HLA三者之间的潜在联系,设计了网格环境下以Web服务为中心的分布式仿真资源框架,在该框架中所有仿真资源都封装为Web服务.最后重点研究了HLA仿真系统中的联邦资源重用问题,对仿真服务的描述和仿真联邦的组合进行了深入的探讨和具体的设计,论证了方案的可行性.     

Resource Space Grid: model,method and platform

A Resource Space Grid is a virtual Grid that aims at effectively sharing, using and managing versatile resources across the Internet. The kernel of the Resource Space Grid includes a Resource Space Model (RSM) and a uniform Resource Using Mechanism (RUM). This paper presents the Resource Space Grid's core scientific issues and methodology, architecture, model and theory, design criteria and method, and practice. A normal form theory is proposed to normalize the resource space—a coordinate system for uniformly specifying and organizing resources. The RUM provides not only the end‐users with an operable resource browser to operate resources using the built‐in Resource Operation Language (ROL), but also the application developers with the ROL‐based programming environment. The prototype platform based on the proposed model and method has been implemented and used for sharing and managing resources in distributed research teams. Operations on Resource Spaces can constitute the virtual communities of Resource Space Grids—a platform independent resource sharing environment. Copyright © 2004 John Wiley & Sons, Ltd.     

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     

网格工作流中基于商品市场的服务选择

服务选择是网格工作流的重要环节。针对现有Web服务组合方法对服务质量（QoS）贪婪索取而不利于网格资源有效利用的问题,提出基于商品市场的"按需"网格服务选择方法：根据面向工作流全局的评价模型,以服务使用者需求为约束条件,将服务选择建模为0-1多维背包问题;并引入经济学中的"价格-供需关系"改进了服务选择模型。仿真实验表明：基于商品市场的服务选择均衡了系统负载,有利于网格资源的高效利用。     

A Market-Oriented Grid Directory Service for Publication and Discovery of Grid Service Providers and their Services

The emergence of Grids as a platform for sharing and aggregation of distributed resources increases the need for mechanisms that allow an efficient management of resources. The Grid economy has been identified as one of the potential solutions as it helps in managing the supply and demand for resources and enables sustained sharing of resources by providing economic incentive for Grid resource providers. An economy based Grid computing environment needs to support an infrastructure that enables the creation of a marketplace for meeting of providers and consumers. This paper presents the Grid Market Directory (GMD) that serves as a registry for publication and discovery of Grid service providers and their services.     

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.     

Grid resource discovery based on distributed learning automata

This paper focuses on resource discovery problem for Grid. Grid is a devices and services environment that has evolved with the goal of resource sharing. Grid resource discovery encompasses locating and retrieving computational resources. Existing resource discovery solutions are not well adapted to the dynamicity and heterogeneity of Grid. Query propagation is a novel approach that forwards an unsupported query from its resident peer to an adjacent peer. The concept of next generation intelligent Grid environments needs intelligent modules for resource discovery. Learning automaton is a stochastic tool with learning ability which simply adapts to the progressive environmental changes. The proposed method utilizes a distributed learning automata (DLA) which is a network of learning automata (LA). Here, multiple DLA are used for forwarding domain-specific queries. Different Grid scales are utilized for evaluation of the proposed method. Results demonstrate that the resource discovery based on DLA optimizes resource utilization, maximizes throughput, minimizes response time and avoids overload. Moreover, the algorithm is also scalable, fully distributed and failure-free.     

Building a Peer-to-peer Information System in Grids via Self-organizing Agents

A Grid information system should rely upon two basic features: the replication and dissemination of information about Grid services and resources, and the distribution of such information among Grid hosts. This paper examines an approach based on ant systems to replicate and map Grid services information on Grid hosts according to the semantic classification of such services. The Ant-based Replication and MApping Protocol (ARMAP) is used to disseminate resource information by a decentralized mechanism, and its effectiveness is evaluated by means of an entropy index. Information is disseminated by agents – ants – that traverse the Grid by exploiting P2P interconnections among Grid hosts. A mechanism inspired by real ants’ pheromone is used by each agent to autonomously drive its behavior on the basis of its interaction with the environment. “Swarm Intelligence” emerges from the activity of a high number of ants. The ARMAP protocol enables the use of a semi-informed search algorithm which can drive query messages towards a cluster of peers having information about resources belonging to the requested class. A simulation analysis has been performed to evaluate the performance of ARMAP.     

网格服务复制机制的研究

网格的OGSA模型要求网格上一切资源都是服务,实现对网格服务的复制可以解决网格中网格服务的访问瓶颈、负载均衡等问题.现有的网格副本服务技术只能对数据、文件资源等静态资源进行复制,不能对包含软硬件需求的有状态的网格服务进行复制.针对这一问题,我们提出了一种有状态网格服务的复制方法,该方法基于虚拟工作空间、Snapshot和有状态资源模拟技术的原理,实现了对网格服务代码的复制、对网格服务运行所需的软硬件环境的复制和搭建、对网格服务内存数据的复制和对网格服务使用的有状态资源的复制.