网格环境中数据统一访问的设计和实现

网格中汇集了大量分布、异构、多管理域的数据资源,使得网格用户对数据的访问变得非常复杂,必须为用户提供行之有效的方法,实现方便、高效、透明、统一的数据访问。本文描述了基于操作系统之上的文件层面的数据统一访问实现方法。这种方法采用虚拟数据集的机制将汇聚在网格中的存储系统抽象成一个虚拟一体化系统,实现了网格数数据的统一视图和一种网格环境中的数据统一访问方法。     

基于网格服务的数据发布系统

网格的核心任务是管理分布在Internet广域环境中的各种类型的软硬件资源，为基于Internet的分布式应用提供一个统一的、虚拟的共享资源的计算平台。如何将数据库资源并入现有的网格架构，满足更加广泛的网格应用的数据访问需求，已经成为一项亟待解决的课题。文章提出了一套网格环境中的数据发布系统的设计方案，以网格服务的形式封装对数据库的访问，实现跨越异构网络环境、异构操作系统环境和异构数据库平台的统一访问模式，从而将数据库资源加入到网格环境中。     

Griddaen数据网格系统的设计与关键技术实现

科学计算领域中的科学数据呈现爆炸式增长，未来的科学计算将以数据为中心，数据网格计算技术成为解决复杂海量科学数据的访问和管理的一种有效技术。设计和实现的Gfiddaen数据网格系统，可以管理多个分布异构的存储资源的数据，为用户提供统一的数据访问。重点介绍了数据网格系统体系结构，以及系统的设计原则和目标，并讨论了系统主要关键技术的实现。     

网格环境下的数据库访问和集成

为了集成网格环境中的数据库资源,促进网格应用支持现有数据库的访问,提出一种基于服务的数据库访问和集成系统(GridDBAdmin)。GridDBAdmin为用户提供了虚拟的全局逻辑数据库视图,支持用户使用现有的SQL语言同时访问多个数据库。系统由元数据服务和网格虚拟数据库服务构成。其中元数据服务负责发现含有用户所需数据的数据库,网格虚拟数据库服务提供全局逻辑视图,通过分布式查询机制将用户的SQL请求分解到具体的数据库中并进行结果合并。对基于Globus和OGSA-DAI工具包开发的原型系统进行了测试,得到了较好的结果。     

网格数据库管理模型与策略

越来越多的网格应用需要管理大容量和广域分布的数据。开放网格服务体系结构中的网格服务提供了动态创建、管理和在网格服务中交换的一致接口。本文探讨了以OGSA网格服务管理网格数据库的模型，网格数据库服务提供支持数据访问的控制和发现、执行数据管理的操作，实现数据资源的虚拟化，通过网格实现现有数据库的访问与集成。同时讨论了相关的优化策略。     

基于网格技术的分布式数据库OLAP应用

引入网格技术来处理分布式数据库,在网格环境下访问已有数据库,提供一个访问不同数据资源的统一接口,并在此基础上将已有的数据库动态地组成一个虚拟数据库完成某一特定任务。用OLAP工具进行数据的预测、分析和决策。最后以某市工商系统分布式业务数据为基础,设计了网格环境下数据集成的原型架构——GOLAPS,并采用模块化的设计方法,以网格服务的形式加以实现,服务之间通过标准的接口进行通信。     

网格环境中模式复用的异构数据库访问和集成方法

如何为网格环境的资源使用者提供异构数据库资源的全局统一视图和一致访问接口,是网格技术及其应用的关键问题和研究热点.由于大学数字博物馆网格(university digital museum grid,简称UDMGrid)需要整合和共享分布在8个城市12个大学数字博物馆的异构数据库资源,因此提出了一种网格环境下模式复用的异构数据库访问和集成方法(database access and integration in UDMGrid,简称UDMGrid-DAI).该方法首先提出了一种模式复用的虚拟数据库构建策略,定义了异构数据库资源的全局统一视图;在此基础上给出了数据库资源注册方式和虚拟数据库查询映射方法,为资源使用者提供了访问数据库的一致访问接口;最后,在UDMGrid的异构数据库资源环境下,实验了从数据库资源注册到使用的全过程,验证了UDMGrid-DAI方法的正确性和实用性.     

网格环境下数据库系统的整合研究

分析了在网格情况下数据库系统所面临的新情况，着重分析了单点访问源和多点访问源两种主要的数据库访问模式。阐述了中科院数据网格项目中数据库统一访问的体系结构，及其主要部件的功能实现。最后对项目经验进行了总结。     

基于OGSA-DAI的数据集成模型研究

随着网格技术应用研究的发展,网格计算环境下数据库访问和集成现成为研究热点。以OGSA-DAI和异构数据库集成技术为基础,概述了数据集成的关键技术,提出了基于OGSA-DAI的数据集成模型,重点讨论了模型的体系结构、数据集成的步骤和实现方法,并以开发的基于此模型的虚拟数据库作为应用实例,验证了所提出模型的有效性。     

网格环境中基于Web服务的DAI中间件的设计与实现

分析和研究了网格环境中数据访问和集成(data access and integration,DAI)需求,结合中间件技术的特点,提出了具有N层应用体系结构的DAI中间件实现策略,即在不同种类的数据资源和网格应用之间构建了一个中间层软件--"虚拟数据库系统",经授权认证的合法用户可通过"虚拟数据库系统"提供的标准访问接口及统一数据格式对网格环境中各种分布的、异构的、不同种类的数据资源进行动态访问和集成.     

GEMLCA: Running Legacy Code Applications as Grid Services

There are many legacy code applications that cannot be run in a Grid environment without significant modification. To avoid re-engineering of legacy code, we developed the Grid Execution Management for Legacy Code Architecture (GEMLCA) that enables deployment of legacy code applications as Grid services. GEMLCA implements a general architecture for deploying legacy applications as Grid services without the need for code re-engineering, or even access to the source files. With GEMLCA, only a user-level understanding is required to run a legacy application from a standard Grid service client. The legacy code runs in its native environment using the GEMLCA resource layer to communicate with the Grid client, thus hiding the legacy nature of the application and presenting it as a Grid service. GEMLCA as a Grid service layer supports submitting jobs, getting their results and status back. The paper introduces the GEMLCA concept, its life cycle, design and implementation. It also presents as an example a legacy simulation code that has been successfully transformed into a Grid service using GEMLCA.     

一种基于网格服务的数据库元数据管理框架

该文主要针对数据网格的分布式异构数据库环境,提出一种基于网格服务来实现数据库元数据采集、存储、查询功能的参考框架。文章讨论了对于异构数据库的元数据,如何实现动/静态信息的管理。通过扩展GlobusToolkit中的MDS(MonitoringandDiscoverService)目录服务模块,使其支持后台关系型数据库,来存储静态元数据,而利用信息采集程序(InformationProvider)来生成动态元数据。整个系统框架建立在网格服务(GridService)基础之上,以网格服务方式提供元数据的访问功能。     

An overview of S-OGSA: A Reference Semantic Grid Architecture

The Grid's vision, of sharing diverse resources in a flexible, coordinated and secure manner through dynamic formation and disbanding of virtual communities, strongly depends on metadata. Currently, Grid metadata is generated and used in an ad hoc fashion, much of it buried in the Grid middleware's code libraries and database schemas. This ad hoc expression and use of metadata causes chronic dependency on human intervention during the operation of Grid machinery, leading to systems which are brittle when faced with frequent syntactic changes in resource coordination and sharing protocols.The Semantic Grid is an extension of the Grid in which rich resource metadata is exposed and handled explicitly, and shared and managed via Grid protocols. The layering of an explicit semantic infrastructure over the Grid Infrastructure potentially leads to increased interoperability and greater flexibility.In recent years, several projects have embraced the Semantic Grid vision. However, the Semantic Grid lacks a Reference Architecture or any kind of systematic framework for designing Semantic Grid components or applications. The Open Grid Service Architecture (OGSA) aims to define a core set of capabilities and behaviours for Grid systems. We propose a Reference Architecture that extends OGSA to support the explicit handling of semantics, and defines the associated knowledge services to support a spectrum of service capabilities. Guided by a set of design principles, Semantic-OGSA (S-OGSA) defines a model, the capabilities and the mechanisms for the Semantic Grid.We conclude by highlighting the commonalities and differences that the proposed architecture has with respect to other Grid frameworks.     

Managing Role-Based Access Control Policies for Grid Databases in OGSA-DAI Using CAS

In this paper, we present a role-based access control method for accessing databases through the Open Grid Services Architecture – Data Access and Integration (OGSA-DAI) framework. OGSA-DAI is an efficient Grid-enabled middleware implementation of interfaces and services to access and control data sources and sinks. However, in OGSA-DAI, access control causes substantial administration overhead for resource providers in virtual organizations (VOs) because each of them has to manage a role-map file containing authorization information for individual Grid users. To solve this problem, we used the Community Authorization Service (CAS) provided by the Globus Toolkit to support the role-based access control (RBAC) within OGSA-DAI. CAS uses the Security Assertion Markup Language (SAML). Our method shows that CAS can support a wide range of security policies using role-privileges, role hierarchies, and constraints. The resource providers need to maintain only the mapping information from VO roles to local database roles and the local policies in the role-map files, so that the number of entries in the role-map file is reduced dramatically. Also, unnecessary authentication, mapping and connections can be avoided by denying invalid requests at the VO level. Thus, our access control method provides increased manageability for a large number of users and reduces day-to-day administration tasks of the resource providers, while they maintain the ultimate authority over their resources. Performance analysis shows that our method adds very little overhead to the existing security infrastructure of OGSA-DAI.     

A replicated information system to enable dynamic collaborations in the Grid

The main advantage of Grid computing over other distributed computing paradigms is its capability to coordinate the access to data and resources in a virtual multi‐institutional environment. To this end, the information system plays a decisive role in selecting the services that meet the applications' needs. This paper presents an information system for the Grid that provides transparent and scalable group communication services to standard Grid applications, with the objective of supporting dynamic collaborations that could help address problems that involve only some participants of a virtual organization. In particular, it enables more flexible delivery mechanisms, which allows applications to select the appropriate services before sending their data to the information system. This significantly enhances the protection of data from unauthorized access, and avoids the transmission of unnecessary messages over the network. The proposed information system is based on the use of XML technologies and replication. It introduces several new advanced features that are not currently supported as a whole by any Grid middleware, such as: several entry points to the information, persistent capabilities, support for advanced queries based on XQuery, and support for the industrial standard WS‐Policy. The information system has been stress tested under realistic workloads in a Grid infrastructure with 50 sites. Scalability has been evaluated in up to 1000 messages that can be up to 10KB in size each, updated with a frequency of 5min. Copyright © 2012 John Wiley & Sons, Ltd.     

ROAM: An Authorization Manager for Grids

The Resource Oriented Authorization Manager (ROAM) was created to provide a simple but flexible authorization system for the FusionGrid computational Grid. ROAM builds on and extends previous community efforts by both responding to access authorization requests and by providing a Web interface for resource management. ROAM works with the Globus Resource Allocation Manager (GRAM), and is general enough to be used by other virtual organizations that use Globus middleware or X.509/TLS authentication schemes to secure a Grid of distributed resources. In addition to describing ROAM, this paper discusses the basic design parameters of a Grid authorization system and the reasons for the choices made in the ROAM design.     

GeneGrid: Architecture, Implementation and Application

The emergence of Grid computing technology has opened up an unprecedented opportunity for biologists to share and access data, resources and tools in an integrated environment leading to a greater chance of knowledge discovery. GeneGrid is a Grid computing framework that seamlessly integrates a myriad of heterogeneous resources spanning multiple administrative domains and locations. It provides scientists an integrated environment for the streamlined access of a number of bioinformatics programs and databases through a simple and intuitive interface. It acts as a virtual bioinformatics laboratory by allowing scientists to create, execute and manage workflows that represent bioinformatics experiments. A number of cooperating Grid services interact in an orchestrated manner to provide this functionality. This paper gives insight into the details of the architecture, components and implementation of GeneGrid.