基于XML分布式数据库查询技术的研究
摘要
分布式数据库系统是物理上分散而逻辑上集中的数据库系统。分布式数据库的使用提高了数据库系统的可靠性、可扩展性、信息容量以及部门协同工作等各方面的能力。但随着Internet的飞速发展，为提供和获取信息资源，接入网络中的计算机越来越多。目前，在全球网络中已有无数的数据库系统在提供信息服务，而且这个数字仍在加速上升。面对如此众多的各种各样的网络异构数据源集合，产生了应该如何对这些信息进行查询等问题。而传统的分布式数据库技术难以解决这个问题。
XML作为一种全球统一的数据表示标准，它的出现为解决上述问题提供了理想的解决方案。因为作为Internet上数据传送的新标准，XML不仅能作为数据内容传输的载体，它还能准确地反映数据结构，并且实现了数据显示与数据内容的分离，使得数据该数据可以在任何平台、任何程序中都可以使用，是在互联网上进行数据交换和数据精确查询的理想工具。
本文围绕着在分布式异构数据库系统上如何实现分布式查询的问题，展开了研究和讨论，提出了基于XML技术的分布式异构数据库查询方案。
首先，针对复杂网络环境中不同类型数据库产品所造成的系统异构性，研究了通过数据库与XML数据模型的结合，以此来实现在各异构系统间数据交换处理的统一，为分布式数据库系统集成提供统一平台。
其次，在第一步基础上，根据XML与数据库结合方式的不同，剖析了分布式数据库的组成结构，并根据层次结构对分布式数据库划分类型。探讨了XML在不同层次上与分布式数据库的结合，并建立统一XML视图的问题，并筛选出可行的实现方案。
最后，针对分布式数据库系统存在于不可预料的复杂网络环境，提出了基于XML的查询方法，以及查询的错误处理与优化方案。
解决分布式异构数据库的查询问题，其实就是利用XML与数据库的紧密结合，使得在各个分布式异构数据库上建立统一数据模型视图成为可能。并处理好分布环境中的查询控制机制。
This paper was written with the goal of creating a complete picture of the XML's place in the today's distributed database applications. It also identifies the related research problems.
The reasons for conceiving XML were presented at the beginning of the paper, as was its broad applicability. Terms like: standard for data exchange, separation of presentation and data, tool for defining new languages etc. were associated with XML.
Then, the approaches and the implications of database XML-ization were considered. XML enabled databases and native XML databases were treated separately and in more detail. It was shown that it is still not clear what kind of XML database will prevail in the battle for XML management. For now, when making an engineering decision on selecting between those two types of XML databases, one must consider application requirements. Two large groups of applications, data-centric and document-centric were mentioned. It was concluded that there is no unique globally satisfying XML database solution.
Finally, focus was switched to distributed database systems dealing with XML. Classification was presented in the paper to slice up and consider separately the introduction of XML to different parts of distributed database architecture. Major approaches and challenges to efficient distributed XML query execution were also discussed.
XML作为一种全球统一的数据表示标准，它的出现为解决上述问题提供了理想的解决方案。因为作为Internet上数据传送的新标准，XML不仅能作为数据内容传输的载体，它还能准确地反映数据结构，并且实现了数据显示与数据内容的分离，使得数据该数据可以在任何平台、任何程序中都可以使用，是在互联网上进行数据交换和数据精确查询的理想工具。
本文围绕着在分布式异构数据库系统上如何实现分布式查询的问题，展开了研究和讨论，提出了基于XML技术的分布式异构数据库查询方案。
首先，针对复杂网络环境中不同类型数据库产品所造成的系统异构性，研究了通过数据库与XML数据模型的结合，以此来实现在各异构系统间数据交换处理的统一，为分布式数据库系统集成提供统一平台。
其次，在第一步基础上，根据XML与数据库结合方式的不同，剖析了分布式数据库的组成结构，并根据层次结构对分布式数据库划分类型。探讨了XML在不同层次上与分布式数据库的结合，并建立统一XML视图的问题，并筛选出可行的实现方案。
最后，针对分布式数据库系统存在于不可预料的复杂网络环境，提出了基于XML的查询方法，以及查询的错误处理与优化方案。
解决分布式异构数据库的查询问题，其实就是利用XML与数据库的紧密结合，使得在各个分布式异构数据库上建立统一数据模型视图成为可能。并处理好分布环境中的查询控制机制。
This paper was written with the goal of creating a complete picture of the XML's place in the today's distributed database applications. It also identifies the related research problems.
The reasons for conceiving XML were presented at the beginning of the paper, as was its broad applicability. Terms like: standard for data exchange, separation of presentation and data, tool for defining new languages etc. were associated with XML.
Then, the approaches and the implications of database XML-ization were considered. XML enabled databases and native XML databases were treated separately and in more detail. It was shown that it is still not clear what kind of XML database will prevail in the battle for XML management. For now, when making an engineering decision on selecting between those two types of XML databases, one must consider application requirements. Two large groups of applications, data-centric and document-centric were mentioned. It was concluded that there is no unique globally satisfying XML database solution.
Finally, focus was switched to distributed database systems dealing with XML. Classification was presented in the paper to slice up and consider separately the introduction of XML to different parts of distributed database architecture. Major approaches and challenges to efficient distributed XML query execution were also discussed.
引文
[1]．胡彬华，异构分布式数据库系统集成的研究与实现，计算机应用研究，2002
[2]．朱文凯，面向Internet的分布式数据库的开发，计算机与现代化，2002
[3]．李巍 丛治琪，异构分布式数据库及其实现机制，2001
[4]．柴晓路，XML数据环境下基于关系模式的数据交换方法，http://ww-900.ibm.com/developerWorks/cn/xml/x-rdb/index.shtml, 2001
[5]．万常选，基于XML的Web数据库技术，计算机与现代化，2002
[6]．王春枝 纪利群，利用XML实现异构数据库间互访，微型机与应用，2002
[7]. Canonical XML, Version 1.0, W3C Recommendation 15 March 2001,/TR/xml-c14n
[8]. XML Schema Part 2: Datatypes, W3C Recommendation 02 May 2001,/TR/xmlschema-2
[9]. XQuery 1.0 and XPath 2.0 Data Model, W3C Working Draft 30 April 2002,/TR/query-datamodel
[10]. XSL Transformations (XSLT), Version 1.0, W3C Recommendation 16 November1999,FFR/xslt
[11]. Web Services Activity, /2002/ws
[12]. Document Object Model (DOM),/DOM
[13]. XML Schema,/XML/Schema
[14]. XQueryX,/TR/xqueryx
[15]. XML Path Language (XPath),/TR/1999/REC-xpath-19991116
[16]. Naming and Addressing: URIs, URLs, ...,/Addressing/
[17]. XML Query,/XML/Query
[18] Alin Deutch, Mary Fernandez, Dan Suciu, "Storing Semistructured Data with STORED," Proc. ACM-SIGMOD Conf., 1999, pp. 431-442.
[26] Daniela Florescu, Donald Kossmann, "A Performance Evaluation of Alternative Mapping Schemes for Storing XML Data in a Relational Database," INRIA Research Report, 1999.
[27] XML:DB InJtiative, "What Js an XML database?," http://www.xmldb.org
/faqs.html#faq-1
[28] Ronald Bourret, "XML and Databases," http://www.rpbourret.com/xml/XMLAndDatabases.htm
[29] Daniela Florescu, Donald Kossmann, loana Manolescu, "Integrating keyword search into XML query processing," Proc. of the 9th WWW Conf., Amsterdam, NL, May 2000.
[30] Alex Bcrson, "Client Server Architecture," McGraw-Hill series on computer communications, 1996.
[31] Donald Kossmann, "The State of the Art in Distributed Query Processing, "ACM Computing Surveys, vol. 32, no. 4, 2000, pp. 422-469.
[32] Roelof van Zwol, "Modelling and searching web-based document collections," PhD thesis, CTIT, Twente University, Netherlands, 2002.
[33] Jayavel Shanmugasundaram et al, "Querying XML Views of Relational Data,"Proceedings of the27th VLDB, 2001, pp. 261-270.
[34] Ioana Manolescu, Daniela Florescu, Donald Kossmann, "Answering XML Queries over Heterogeneous Data Sources," Proc. of 27th Int'l Conf. Very Large Data Bases (VLDB'01, Rome, Italy), Morgan Kaufmann, 2001, pp. 241-250.
[35] Patricia Rodriguez-Gianolli, "ToX-The Toronto XML Engine," Workshop on Information Integration on the Web, Rio de Janeiro, 2001.
[38] Nalin Gupta, Jayant Haritsa, Maya Ramanath, "Distributed Query Processing on the Web," 16th International Conference on Data Engineering (ICDE), 2000, pp. 84.
[37] Jeffrey Naughton et al, "The Niagara Internet Query System," http ://www.cs.wisc.edu/niagara
[38] The Tukwila Data Integration System, http://data.cs.washington.edu/integration/
[39] Jayavel Shanmugasundaram et al, "Architecting a network query engine for producing partial results," In WebDB (Informal Proceedings) 2000, pages 17-22,2000.
[2]．朱文凯，面向Internet的分布式数据库的开发，计算机与现代化，2002
[3]．李巍 丛治琪，异构分布式数据库及其实现机制，2001
[4]．柴晓路，XML数据环境下基于关系模式的数据交换方法，http://ww-900.ibm.com/developerWorks/cn/xml/x-rdb/index.shtml, 2001
[5]．万常选，基于XML的Web数据库技术，计算机与现代化，2002
[6]．王春枝 纪利群，利用XML实现异构数据库间互访，微型机与应用，2002
[7]. Canonical XML, Version 1.0, W3C Recommendation 15 March 2001,/TR/xml-c14n
[8]. XML Schema Part 2: Datatypes, W3C Recommendation 02 May 2001,/TR/xmlschema-2
[9]. XQuery 1.0 and XPath 2.0 Data Model, W3C Working Draft 30 April 2002,/TR/query-datamodel
[10]. XSL Transformations (XSLT), Version 1.0, W3C Recommendation 16 November1999,FFR/xslt
[11]. Web Services Activity, /2002/ws
[12]. Document Object Model (DOM),/DOM
[13]. XML Schema,/XML/Schema
[14]. XQueryX,/TR/xqueryx
[15]. XML Path Language (XPath),/TR/1999/REC-xpath-19991116
[16]. Naming and Addressing: URIs, URLs, ...,/Addressing/
[17]. XML Query,/XML/Query
[18] Alin Deutch, Mary Fernandez, Dan Suciu, "Storing Semistructured Data with STORED," Proc. ACM-SIGMOD Conf., 1999, pp. 431-442.
[26] Daniela Florescu, Donald Kossmann, "A Performance Evaluation of Alternative Mapping Schemes for Storing XML Data in a Relational Database," INRIA Research Report, 1999.
[27] XML:DB InJtiative, "What Js an XML database?," http://www.xmldb.org
/faqs.html#faq-1
[28] Ronald Bourret, "XML and Databases," http://www.rpbourret.com/xml/XMLAndDatabases.htm
[29] Daniela Florescu, Donald Kossmann, loana Manolescu, "Integrating keyword search into XML query processing," Proc. of the 9th WWW Conf., Amsterdam, NL, May 2000.
[30] Alex Bcrson, "Client Server Architecture," McGraw-Hill series on computer communications, 1996.
[31] Donald Kossmann, "The State of the Art in Distributed Query Processing, "ACM Computing Surveys, vol. 32, no. 4, 2000, pp. 422-469.
[32] Roelof van Zwol, "Modelling and searching web-based document collections," PhD thesis, CTIT, Twente University, Netherlands, 2002.
[33] Jayavel Shanmugasundaram et al, "Querying XML Views of Relational Data,"Proceedings of the27th VLDB, 2001, pp. 261-270.
[34] Ioana Manolescu, Daniela Florescu, Donald Kossmann, "Answering XML Queries over Heterogeneous Data Sources," Proc. of 27th Int'l Conf. Very Large Data Bases (VLDB'01, Rome, Italy), Morgan Kaufmann, 2001, pp. 241-250.
[35] Patricia Rodriguez-Gianolli, "ToX-The Toronto XML Engine," Workshop on Information Integration on the Web, Rio de Janeiro, 2001.
[38] Nalin Gupta, Jayant Haritsa, Maya Ramanath, "Distributed Query Processing on the Web," 16th International Conference on Data Engineering (ICDE), 2000, pp. 84.
[37] Jeffrey Naughton et al, "The Niagara Internet Query System," http ://www.cs.wisc.edu/niagara
[38] The Tukwila Data Integration System, http://data.cs.washington.edu/integration/
[39] Jayavel Shanmugasundaram et al, "Architecting a network query engine for producing partial results," In WebDB (Informal Proceedings) 2000, pages 17-22,2000.