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Understanding XPath and Trees in XML: A Comprehensive Guide

Explore XPath language to locate data in XML documents through tree views and path syntax. Learn about steps, paths, operators, syntax rules, and practical examples. Discover how to process text values efficiently in XSLT.

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Understanding XPath and Trees in XML: A Comprehensive Guide

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  1. XPath and trees Elena Pierazzo 2006-2007

  2. XPath • A language to describe how to locate a part of an XML document • Used in many XML-based technologies and tools

  3. XML documents: a tree view <p>Here is some <hi type="ital">highlighted</hi> text.</p> node link

  4. Or a genealogical chart Parent of <p> Ancestor of <hi>, @type, text nodes Child of / Siblings, descendant of /

  5. Other examples Let’s see some more examples

  6. Paths and Steps one step’s path <xsl:template match=“section”> <xsl:template match=“section/title”> / step operator (= child of) two steps’ path

  7. Abbreviated Syntax • / = child of E.g.: “section/title” Not the same as: /section/title • // = descendant of E.g.: “body//title” • * = any node E.g.: body/*/title • . = current node E.g.: .//para Not the same as //para

  8. XPath at work <AUTHOR TYPE="main">  <NAME><FIRST>Professor Christopher</FIRST><LAST>Gantley</LAST></NAME>  <AFFIL>University of Northumbria</AFFIL>  <EMAIL>c.gantley@unnx.ac.uk</EMAIL></AUTHOR><AUTHOR>  <NAME><FIRST>Megan</FIRST><LAST>Graham</LAST></NAME>  <AFFIL>Institute of Image Research, University of Northumbria</AFFIL>  <EMAIL>megan.graham@unnx.ac.uk</EMAIL></AUTHOR>

  9. We want obtain: Gantley, Professor Christopher <xsl:template match="NAME"><Ii><xsl:apply-templates select="LAST"/>, <xsl:apply-templates select="FIRST"/></i></xsl:template> Children of the contextual node Contextual node

  10. The select attribute • Has different meaning! • <xsl:template match=“node and descendant”> • <xsl:apply-templates select=“selected node”> • <xsl:value-of select=“text”>  forthcoming!

  11. Processing the text: value-of As it was: http://www.cch.kcl.ac.uk/legacy/teaching/av2001/xslt/class_mats/chap1/examples/eeyore.xsl How we can making it better: <xsl:template match="story"><html><head><title>Winnie-the-Pooh: <xsl:value-of select="/story/title"/></title></head><body><xsl:apply-templates/></body></html></xsl:template> Just text, not other nodes

  12. More examples • XML document: chap 2 > examples > abst10.xml • "Finished" template: chap 2 > examples > abstrs.xsl

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