摘要
随着Internet的发展，可扩展标记语言XML(eXtensible Markup Language)正逐渐成为互联网上数据发布和交换的标准。由于其强大的数据表达能力和嵌套的结构、自描述的特点，XML可以在互联网和数据库之间扮演更为重要的角色。然而，目前企业的大量数据仍存在于占主导地位的关系数据库中，如何在现有的数据库平台上以XML形式准确地表达关系数据，已成为亟待解决的关键问题。
本文的研究以MDA(Model Driven Architecture，模型驱动的体系架构)作为指导思想，分别从模式层和实例层的角度探讨了关系数据库的XML发布技术。本文第一部分从XML和关系数据库的技术特点入手，分析了用XML发布企业关系数据库的必要性和可行性。
接着，是本文的主要工作之一：分析了XML Schema和关系模式的语义约束特征，总结了关系模式到XML文档模式的一般转换规则；在此基础上，提出了构建XML视图模式结构图的两种典型策略。
本文的第三部分比较了几个主流数据库厂商提供的XML动态发布技术；并选择以Oracle的产品作为实验工具，详细剖析了Oracle发布函数的使用特点。
最后，给出企业数据库的XML发布模型，并根据该模型提出了可自动生成XML视图的XViews-Generator工具。同时结合一个气象数据库的XML发布系统的应用案例说明了上述技术：即运用XViews-Generator工具的实现原理，根据源气象关系数据库的相关信息，获得可选的XML视图模式文档，再结合动态的查询得到XML实例文档，从而实现气象关系数据库的XML发布。
本文以RDB作为底层数据载体，研究了通过在其上建立XML视图实现数据发布的方法。本文落点于XML视图模式文档结构的设计方案的研究，有机地将静态映射规则与动态查询技术结合起来实现了企业数据库的XML发布。
With the exponential growth of Internet, XML(eXtensible Markup Language) isbecoming a de-facto standard for data publishing and data exchange. Due to its highexpressiveness and nested structure, self-describing characteristic, XML can play amore important role than Relational Database does in connecting Database withInternet. While at the present time most business data are still stored in traditionalrelational database systems, how to transform data from existing relational databaseinto XML representation has become the pivotal problem to be resolved.
Some discussions have been done about the technology of publishing XMLdocuments from RDB at the viewpoint of both schema and instance, guided by thepopular MDA principle. We analyze the necessity and feasibility of publishing XMLfrom RDB according to the features of XML and RDB in the first part of this thesis.
The following is one of the main contributions in this thesis: Two strategies areproposed to design XML views schema structure by analyzing the semanticconstraints characteristics of both XML Schema and relational schema andsummarizing the general transformation rules from relational schema to XMLdocument schema.
In the third part we compare several techniques of XML publishing provided bythe mainstream manufacturers of database. And we choose Oracle as the test-bed byanalyzing the characteristics of XML publishing functions provided by Oracledatabase.
At last, a publishing model of enterprise database is brought forward.Correspondingly a tool named XViews-Generator which can automatically generateXML views schema is implemented. At the same time a case about the publishing ofweather database is introduced to illustrate the techniques mentioned above: Utilizingthe realization principle of XViews-Generator to get the candidate XML viewsschema according to the main information of weather database and on the basis ofthis dynamic query techniques are used to implement the XML publishing from weather database.
The publishing technique is studied in which the RDB is taken as the bottomstoring medium and the upper XML views are set up in this thesis. To implement theXML publishing from RDB, the thesis establish two strategies of designing XMLviews schema structure combining the static mapping rules with the dynamic queries.
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