III:Next Generation XML Mediators

以前对数据集成的研究主要集中在XML中介体上，它为应用程序提供了一个虚拟的集成的XML视图，允许单点访问多个分布式和异类信息源的数据。随后的工业产品针对企业信息集成并遵循全局即视图的范例，其中所有者将集成的视图指定为源视图的XQuery函数。面向服务的体系结构的出现和基于Internet的大规模数据集成的出现，使得基于全局即视图的信息不足以从新出现的机会中获益，并且在大规模环境中效率低下。面向服务的体系结构通过向数据集提供一组Web服务调用来提供实时数据访问，这在大规模环境中是无效的大规模的数据集成突出了全局即视图示例所造成的部署、开发和维护瓶颈，它要求集成视图所有者了解所有数据源的模式、数据格式和语义。所提出的中介器通过在XML环境中采用新的全局本地即视图示例提供了一种可扩展的解决方案：每个源所有者都可以负责将其源数据和Web服务与集成视图相匹配。该范例的实现需要基础的算法和系统创新。首先，必须重写集成视图上的查询以使用源服务和数据。现有的重写关系视图上的关系查询的算法是不够的，因为它们没有解决服务和丰富的XML查询结构。其次，源代码所有者需要适当的语言和可视化工具来导出界面，其范围可以是对底层数据库的完全访问，也可以是几个参数查询以及介于两者之间的任何地方。上述基本贡献的解决将有助于UCSD-XMED XQuery中介器重写模块的开发，它可以成为一个有价值的信息共享和发布组件，特别是对于科学门户网站，科学家们将他们的实验数据数据库连接到基于XML的门户网站，以实现对科学信息的综合访问。UCSD-XMED查询处理器将供数据库和中间件技术专业的研究生和本科生使用。有关该项目的最新信息，包括人员、软件分发和出版物，请访问http://db.ucsd.edu/NSF07xmlMed/

Prior research on data integration ledto XML mediators, which provide to applications avirtual integrated XML viewthat allows a single point of access to the data ofmultiple distributed and heterogeneous information sources.Consequent industrial products address Enterprise Information Integrationand follow the Global-As-View paradigm,where the owner specifies the integratedview as an XQuery function of the source views.The emergence of Service-Oriented Architecturesand large scale Internet-based data integration, whichis often needed in the science domains,renders Global-As-View-based information insufficient to benefit fromthe emerging opportunities and inefficient in large scale environments.Service-Oriented Architectures provide live data accessat data sets by offering a set of web service calls to them,as opposed to (the studied in prior works) full query access to the data sets.Large scale data integration highlights the deployment, developmentand maintenance bottleneck that the Global-As-View paradigmcreates by requiring the integrated view owner to have knowledgeof the schema, data formats and semantics of all sources.The proposed mediator provides a scalable solutionby employing a new Global-Local-As-View paradigm in an XML setting:Each source owner can become responsible for fitting her sourcedata and web services to the integrated view.Fundamental algorithmic and system innovations are needed for the implementation of the paradigm.First, queries over the integrated view must be rewritten to use the source services and data. Existing algorithms for rewritingrelational queries over relational views are not sufficient, as they do not address services andthe rich structure of XML queries. Second, the source owner needsan appropriate language and visual tools to export interfaces ina way that can range from full access to theunderlying database to a few parameterized queries and anywhereinbetween. Finally, the client needs corresponding systemsto comprehend which XQueries can be asked on the integrated view.The resolution of the above fundamental contributions will enablethe development of the rewriting module of the UCSD-XMED XQuerymediator, which can become a valuable information sharing and publishing component, especially for science portals where scientists will connect their databases of experimental data to XML-based portals for integrated accessto scientific information. The UCSD-XMED query processor will beused by graduate and undergraduate students in database andmiddleware technologies.Updates about the project, including its people, software distributions and publications are available at http://db.ucsd.edu/NSF07xmlMed/