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IT420: Database Management and Organization

Learn about the importance of XML in database processing, its benefits compared to HTML, and how to create and transform XML documents using DTDs and XSLT.

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IT420: Database Management and Organization

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  1. IT420: Database Management and Organization XML 21 April 2006 Adina Crăiniceanu www.cs.usna.edu/~adina

  2. Overview • From HTML to XML • DTDs • Transforming XML: XSLT Kroenke, Database Processing

  3. Introduction • Database processing and document processing need each other • Database processing needs document processing for transmitting/ expressing database views • Document processing needs database processing for storing and manipulating data • Internet expansion made the need obvious Kroenke, Database Processing

  4. XML • XML: Extensible Markup Language, developed in early 1990s • Hybrid of document processing and database processing • It provides a standardized yet customizable way to describe the content of documents • A recommendation from the W3C • XML = data + structure • XML generated by applications • XML consumed by applications • Easy access: across platforms, organizations Kroenke, Database Processing

  5. XML What is this? What does it mean? <h2>Madison</h2> HTML: How to display information on a browser. HTML: no “semantic” information, i.e. no meaning ascribed to tags Kroenke, Database Processing

  6. XML: Semantic information <presidents> <name>Madison</name> <US_cities> <Wisconsin> <name>Madison</name> <US_Colleges> <name>Madison, U of Wisc</name> <name> Madison, James (JMU)</name> Kroenke, Database Processing

  7. XML vs. HTML • XML is better than HTML because It provides a clear separation between document • structure • content • materialization • It is standardized but allows for extension by developers • XML tags represent the semantics of their data Kroenke, Database Processing

  8. Why is XML important with regard to databases? • XML provides a standardized way to describe, validate, and materialize any database view. • Share information between disparate systems • Materialize data anyway you want • Display data on web • Display data on sales-person computer • Display data on mobile device Kroenke, Database Processing

  9. How does XML work? Three Primary Components to XML • Data has a structure • Document Type Declarations (DTDs) • XML Schemas can be used to describe the content of XML documents • Data has content • XML document • Data has materializations • Extensible Style Language: Transformations (XSLT) Kroenke, Database Processing

  10. If we want to share information is structure important? • Structure provides meaning What is the meaning of this bit stream?? 10111011000101110110100101010101101010110110101…. The bit stream has meaning if we assign structure Kroenke, Database Processing

  11. Example: XML DTD & Document Kroenke, Database Processing

  12. XML DTD • XML document consists of two sections: • Document Type Declaration (DTD) • The DTD begins with DOCTYPE <document_type_name> • Document data • XML documents could be • Type-valid if the document conforms to its DTD • Well-formed and not be type-valid, because • It violates the structure of its DTD • It has no DTD • DTD may be stored externally so many documents can be validated against the same DTD Kroenke, Database Processing

  13. Create XML Documents from Relational DB Data • Most RDBMS can output data in XML format • MySQL: mysql –u root --xml • For SQL Server: • SELECT . . . FOR XML RAW | AUTO, ELEMENTS | EXPLICIT Kroenke, Database Processing

  14. Lab exercise • Restore some database in MySQL • Open MySQL command line using • mysql –u root --xml Kroenke, Database Processing

  15. XSLT • XSLT, or the Extensible Style Language may be used to materialize (transform) XML documents using XSL document • From XML documents into HTML or into XML in another format • XSLT is a declarative transformation language • XSLT uses stylesheets to indicate how to transform the elements of the XML document into another format Kroenke, Database Processing

  16. Example: External DTD <?xml version="1.0" encoding="UTF-8"?> <!ELEMENT customerlist (customer+)> <!ELEMENT customer (name, address)> <!ELEMENT name (firstname, lastname)> <!ELEMENT firstname (#PCDATA)> <!ELEMENT lastname (#PCDATA)> <!ELEMENT address (street+, city, state, zip)> <!ELEMENT street (#PCDATA)> <!ELEMENT city (#PCDATA)> <!ELEMENT state (#PCDATA)> <!ELEMENT zip (#PCDATA)> Kroenke, Database Processing

  17. Example: XML Document <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE customerlist SYSTEM "http://localhost/Support-Files-Chap-13-XML/CustomerList.dtd"> <?xml-stylesheet type="text/xsl" href="http://localhost/Support-Files-Chap-13-XML/CustomerList-StyleSheet.xsl"?> <customerlist> <customer> <name> <firstname>Michelle</firstname> <lastname>Correlli</lastname> </name> <address> <street>1824 East 7th Avenue</street> <street>Suite 700</street> <city>Memphis</city> <state>TN</state> <zip>32123-7788</zip> </address> </customer> <customer> <name> <firstname>Lynda</firstname> <lastname>Jaynes</lastname> </name> <address> <street>2 Elm Street</street> <city>New York City</city> <state>NY</state> <zip>02123-7445</zip> </address> </customer> </customerlist> Kroenke, Database Processing

  18. XSL Stylesheet for CustomerList Kroenke, Database Processing

  19. Example: XML  Browser Kroenke, Database Processing

  20. Show XSL document example CustomerList.xml Kroenke, Database Processing

  21. XML Review • STRUCTURE: DTD or XML Schema • CONTENT: XML document • MATERIALIZATIONS: XSL document Kroenke, Database Processing

  22. Sharing Data: Transparency Agreed upon structure Database Raw data Database Raw data XML data XSL Trans Validate DTD Validate DTD XSL Trans XML data SHARE Business A Business B Kroenke, Database Processing

  23. Example XML Industry Standards • Accounting • Extensible Financial Reporting Markup Language (XFRML) • Architecture and Construction • Architecture, Engineering, and Construction XML (aecXML) • Automotive • Automotive Industry Action Group (AIAG) • XML for the Automotive Industry (SAE J2008) • Banking • Banking Industry Technology Secretariat (BITS) • Bank Internet Payment System (BIPS) • Electronic Data Interchange • Data Interchange Standards Association (DISA) • XML/EDI Group Kroenke, Database Processing

  24. What About XML Queries? • Xpath • A single-document language for “path expressions” • Not unlike regular expressions on tags • E.g. /Contract/*/UnitPrice, /Contract//UnitPrice, etc. • XSLT • XPath plus a language for formatting output • XQuery Kroenke, Database Processing

  25. Conclusions • XML: The new universal data exchange format • Unlike HTML, XML = data + semantics • STRUCTURE: DTD or XML Schema • CONTENT: XML document • MATERIALIZATIONS: XSL document • More flexible than relational model • More difficult to query – research Kroenke, Database Processing

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