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IT420: Database Management and Organization XML 21 April 2006 Adina Crăiniceanu www.cs.usna.edu/~adina
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Kroenke, Database Processing 2 Overview From HTML to XML DTDs Transforming XML: XSLT
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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
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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
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Kroenke, Database Processing 5 XML What is this? What does it mean? Madison HTML: How to display information on a browser. HTML: no “semantic” information, i.e. no meaning ascribed to tags
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Kroenke, Database Processing 6 XML: Semantic information Madison Madison Madison, U of Wisc Madison, James (JMU)
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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
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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
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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)
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Kroenke, Database Processing 10 If we want to share information is structure important? Structure provides meaning 10111011000101110110100101010101101010110110101…. What is the meaning of this bit stream?? The bit stream has meaning if we assign structure
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Kroenke, Database Processing 11 Example: XML DTD & Document
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Kroenke, Database Processing 12 XML DTD XML document consists of two sections: Document Type Declaration (DTD) The DTD begins with DOCTYPE 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
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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
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Kroenke, Database Processing 14 Lab exercise Restore some database in MySQL Open MySQL command line using mysql –u root --xml
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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
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Kroenke, Database Processing 16 Example: External DTD
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Kroenke, Database Processing 17 Example: XML Document
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Kroenke, Database Processing 18 Example: XML Document Michelle Correlli 1824 East 7th Avenue Suite 700 Memphis TN 32123-7788 Lynda Jaynes 2 Elm Street New York City NY 02123-7445
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Kroenke, Database Processing 19 XSL Stylesheet for CustomerList
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Kroenke, Database Processing 20 Example: XML Browser
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Kroenke, Database Processing 21 Show XSL document example CustomerList.xml
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Kroenke, Database Processing 22 XML Review STRUCTURE: DTD or XML Schema CONTENT: XML document MATERIALIZATIONS: XSL document
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Kroenke, Database Processing 23 Sharing Data: Transparency XML data XSL Trans Validate DTD Database Raw data Validate DTD XSL Trans XML data Database Raw data Business A Business B Agreed upon structure SHARE
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Kroenke, Database Processing 24 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
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Kroenke, Database Processing 25 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
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Kroenke, Database Processing 26 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
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