J2EE平台上基于Web Services的数据集成研究

数据集成是共享分布的异构数据资源的核心问题.在分析常用数据集成技术的基础上,结合Web Services技术和组件技术,提出了基于Web Services和组件技术实现Mediated系统的数据集成方案.最后,以J2EE为平台给出了一种面向服务的低偶合的数据集成框架,中介器和包装器由EJB组件实现,由组件部署的Web服务为用户提供一个透明的统一的接口,实现异地异构数据资源的共享和整合.     

A unified interface for integrating information retrieval

In this paper, we propose a unified interface and a flexible architecture for querying various information sources on the Internet and the WWW using both a popular object model and a data model. We propose an Integrated Information Retrieval (IIR) service based on the Common Object Service Specification (COSS) for Common Object Request Broker Architecture (CORBA) and apply the Document Type Definition (DTD) of eXtensible Markup Language (XML) to define the metadata of information sources for sharing the ontology between mediator and wrappers. The objective of using the IIR design is not only to provide programmers with a uniform interface for coding a software application that can query a variety of information sources on the Internet, but also to create a flexible and extensible environment that easily allows system developers to add new or updated wrappers to the system.     

面向异构数据集成的数据源能力描述框架

异构数据源集成系统旨在为用户提供一个一致的访问接口，由于参与集成的各数据源不仅高度自治、模式各异、更新频繁，而且查询功能有各自特殊的限制，给查询处理过程中数据源定位和查询优化造成一定的困难。本文在分析异构集成系统特征和功能需求的基础上，提出一种基于KQML的数据源能力描述框架，为各数据源灵活动态的发布自身能力提供保证。进而通过形式化的规范描述刻画数据源的结构特征和行为特征，为定位查询相关数据源奠定基础．并有助于全局查询处理器对查询计划进行优化，缩减查询的搜索空间，提高查询效率。     

一种统一的可扩展语言UXL及其应用

本文提出一种统一的可扩展语言UXL,它可用于描述Web上数据源、用户查询需求、各种服务、控制流以及事件等。利用UXL可实现对网上数据源和服务的统一描述,从而为各种服务器做一件外观统一的“主动服务外套”,构成所谓的“主动虚拟服务器。此外,还可利用UXL来描述查询计划,实现分布式协同工作和计算,构造可供网上使用的、动态的、可伸缩的分布式协同环境等。     

基于物理隔离的分布式数据库同步

使用安全隔离与信息交换系统对内网和外网进行物理隔离是电子政务建设的先决条件。为了在政务内网和外网的不同数据库环境下实现相互的数据交流和共享,该文提出一种基于XML标准的分布式数据库同步策略。它构造基于XML标准的描述文件和数据转换规则文件的接口层作为隔离层,利用该接口层组装数据包作为传输单位,以解决不同安全级别的网络连接下的数据传输问题。     

基于XML的Web异种数据库操作模型的研究

互连网的迅速发展使得Web数据库成为数据库应用的主流,随着网上数据量的增加,越来越多的应用迫切需要通过网络来交换数据。然而,目前的Web数据库实现技术与数据库在设计结构和平台上的差异给数据库的网络操作带来了实现上的困难,同时数据库操作的网络开放会带来诸多安全隐患。基于此,该文提出了一种基于XML的Web异种数据库操作模型,设计了请求和结果XML文档的一般结构(DTD),讨论了该模型在确保数据库安全的条件下,完成异种数据库在Web上的数据交换和共享的工作过程。     

The mediator authorization-security model for heterogeneous semantic knowledge bases

Many organizations often need to share semantic knowledge base content with selected members of other organizations. However, sharing semantic knowledge across different organizations is a critical problem. This is because the differences in the vocabulary utilized by the organizations have to be resolved before knowledge can be shared. Also, if semantic repositories are syntactically and schematically heterogeneous, information interoperation becomes a vital challenge. When a system needs to allow unknown entities to access its resources, mechanisms should be in place in order to provide a secure and trusted information-sharing environment and enable users to interact and share information easily and perfectly. To address these challenges, the Mediator Authorization-Security model is proposed to provide secure interoperation among heterogeneous semantic repositories. This paper addresses the issue of interoperability and how to incorporate trust into semantic interoperability. The evaluation showed that, despite the complexity of the mediator system, it still provides acceptable performance.     

Scaling access to heterogeneous data sources with DISCO

Accessing many data sources aggravates problems for users of heterogeneous distributed databases. Database administrators must deal with fragile mediators, that is, mediators with schemas and views that must be significantly changed to incorporate a new data source. When implementing translators of queries from mediators to data sources, database implementers must deal with data sources that do not support all the functionality required by mediators. Application programmers must deal with graceless failures for unavailable data sources. Queries simply return failure and no further information when data sources are unavailable for query processing. The Distributed Information Search COmponent (Disco) addresses these problems. Data modeling techniques manage the connections to data sources, and sources can be added transparently to the users and applications. The interface between mediators and data sources flexibly handles different query languages and different data source functionality. Query rewriting and optimization techniques rewrite queries so they are efficiently evaluated by sources. Query processing and evaluation semantics are developed to process queries over unavailable data sources. In this article, we describe: 1) the distributed mediator architecture of Disco; 2) the data model and its modeling of data source connections; 3) the interface to underlying data sources and the query rewriting process; and 4) query processing semantics. We describe several advantages of our system     

异构数据库互操作可视化界面的实现

强大的数据操作功能是异构数据库操作系统所必不可少的。通过它,用户可以透明地访问多个异构数据库。为此,实现了一个基于Ｏｒａｃｌｅ和Ｓｙｂａｓｅ数据库的可视化互操作界面。     

异构数据源集成系统中基于数据源能力的查询分解和优化策略

异构数据源集成系统需要集成查询能力差别较大的各种数据源。为充分利用数据源的查询能力和简化包装器设计,本文提出使用复合法进行基于能力的查询分解和优化。在复合法中,仅需简单说明数据的基本查询能力,各数据源对查询处理的特殊限制封装在包装器中。文中给出描述数据源基本查询能力的方法,并且在讨论ＯＩＭ对象代数操作的概括查询和过滤子的基础上,探讨数据源包装器对基本支持查询的处理方法。     

The Pegasus heterogeneous multidatabase system

Pegasus, a heterogeneous multidatabase management system that responds to the need for effective access and management of shared data across in a wide range of applications, is described. Pegasus provides facilities for multidatabase applications to access and manipulate multipole autonomous heterogeneous distributed object-oriented relational, and other information systems through a uniform interface. It is a complete data management system that integrates various native and local databases. Pegasus takes advantage of object-oriented data modeling and programming capabilities. It uses both type and function abstractions to deal with mapping and integration problems. Function implementation can be defined in an underlying database language or a programming language. Data abstraction and encapsulation facilities in the Pegasus object model provide an extensible framework for dealing with various kinds of heterogeneities in the traditional database systems and nontraditional data sources     

一种多自治域层次互操作模型的系统框架

数据互操作是信息集成领域需要解决的关键问题。联邦数据库和多数据库是解决分布式异构环境中多个数据源的集成与互操作的两种方法,但它们各有优缺点。完全的集中不能保证局部系统的自治,全部的分散又不能保证系统之间的共享和互操作。在分析联邦数据库与多数据库特点与差异的基础上,提出了一种多自治域的层次互操作模型MDHI,通过对Panorama多数据库系统进行扩展,给出了一种基于WebService的PanoramaWebOne系统框架。这种框架既满足了局域范围内的集成和处理效率,又提供了一种集成广域范围内多种异构数据源的方法,更加符合当前实际应用的需要。     

一种跨域网络资源的安全互操作模型

网络资源需要在安全策略控制下共享与互操作。针对多异构安全域域间资源互操作的安全问题,提出了一种基于RBAC安全策略的跨域网络资源的安全互操作模型。首先引入域间角色的概念,并定义跨域资源共享访问的要求;其次在跨域操作准则的基础上,提出异构域间资源安全互操作模型和访问算法;最后以实例场境对模型和算法进行了应用分析。结果表明,该方法针对性强,权限控制有效,为实现多域资源共享和互操作的安全保障提供了一种可行的途径。     

A visual tool for ontology alignment to enable geospatial interoperability

In distributed geospatial applications with heterogeneous databases, an ontology-driven approach to data integration relies on the alignment of the concepts of a global ontology that describe the domain, with the concepts of the ontologies that describe the data in the distributed databases. Once the alignment between the global ontology and each distributed ontology is established, agreements that encode a variety of mappings between concepts are derived. In this way, users can potentially query hundreds of geospatial databases using a single query. Using our approach, querying can be easily extended to new data sources and, therefore, to new regions. In this paper, we describe the AgreementMaker, a tool that displays the ontologies, supports several mapping layers visually, presents automatically generated mappings, and finally produces the agreements.     

REMUS: A Rerouting and Multiplexing System for Grid Connectivity Across Firewalls

The Grid provides unique opportunities for high-performance computing through distributed applications that execute over multiple remote resources. Participating institutions can form a virtual organization to maximize the utilization of collective resources as well as to facilitate collaborative projects. However, there are two design aspects in distributed environments like the Grid that can easily clash: security and resource sharing. It may be that resources are secure but are not entirely conducive to resource sharing, or networks are wide open for resource sharing but sacrifice security as a result. We developed REMUS, a rerouting and multiplexing system that provides a compromise through connection rerouting and wrappers. REMUS reroutes connections using proxies, ports and protocols that are already authorized across firewalls, avoiding the need to make new openings through the firewalls. We also encapsulate applications within wrappers, transparently rerouting the connections among Grid applications without modifying their programs. In this paper, we describe REMUS and the tests we conducted across firewalls using two Grid middleware case studies: Globus Toolkit 2.4 and Nimrod/G 3.0.     

基于分布式OSGi的通用电力数据平台

提升智能电网中各种异构应用软件间的数据共享和功能交互能力,是电力企业亟需解决的问题。而依靠标准化数据模型、SOA等技术的传统交互方案对模块运行期热插拔、分布式编程模型低侵入性和电力数据持续变化的支持度不足。为此,以电力数据为中心,从软件架构角度,将电力应用解耦为数据总线和数据插件,提出一种基于分布式开放式服务网关(OSGi)的通用电力数据平台。阐述平台拓扑架构、分布式OSGi的扩展方法及通用电力元数据模型,给出平台在福建电网的实施方法,并对典型业务模块的功能及并发性能进行测试,结果表明,该平台能有效降低异构电力应用间的数据共享和功能交互难度。     

分布式环境下地理信息互操作技术研究

地理信息系统( GIS ) 的迅速发展产生和积累的大量地理空间数据以不同的存储格式存放于不同地点的不同系统和设备中, 从而对数据的互操作、共享管理和综合利用产生了极其不利的影响。互联网、分布式计算和空间数据库等新技术的发展给空间数据的共享管理带来了难得的机遇,在分析当前GIS 数据互操作相关技术基础上, 对面向分布式的多源异构数据互操作机制进行研究, 提出了解决方案。     

基于XML异构数据库集成中间件的设计与实现

为了解决网络环境中异构数据库数据共享和协作问题,提出了基于XML中间件技术实现异构数据库之间信息交换模型.在此模型中对虚拟法或中介法模型进行改进设计了翻译器、集成器和转换器,分别用于数据获取、合并和格式转换.为了更精确地描述XML文件自身结构信息,实现了从DTD到XML Schema的转换.     

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.     

Metadata for Managing Grid Resources in Data Mining Applications

The Grid is an infrastructure for resource sharing and coordinated use of those resources in dynamic heterogeneous distributed environments. The effective use of a Grid requires the definition of metadata for managing the heterogeneity of involved resources that include computers, data, network facilities, and software tools provided by different organizations. Metadata management becomes a key issue when complex applications, such as data-intensive simulations and data mining applications, are executed on a Grid. This paper discusses metadata models for heterogeneous resource management in Grid-based data mining applications. In particular, it discusses how resources are represented and managed in the Knowledge Grid, a framework for Grid-enabled distributed data mining. The paper illustrates how XML-based metadata is used to describe data mining tools, data sources, mining models, and execution plans, and how metadata is used for the design and execution of distributed knowledge discovery applications on Grids.