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Predicates

Predicates. Elena Pierazzo 2006-2007. Intro. Part of XPath Refine the filtering of selected nodes Only nodes that correspond to the predicates assumption will be considered Syntax: [predicate_content]. E.g. Only elements that have a particular attribute value

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Predicates

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  1. Predicates Elena Pierazzo 2006-2007

  2. Intro • Part of XPath • Refine the filtering of selected nodes • Only nodes that correspond to the predicates assumption will be considered • Syntax: [predicate_content]

  3. E.g. • Only elements that have a particular attribute value • Only elements that have a given position

  4. Select nodes with given attribute values <xsl:template match="p[@audience='Instructor']"> <p><font color="red"><xsl:apply-templates/></font></p> </xsl:template>

  5. Other examples with attributes • p[@audience != 'Instructor']  NOT EQUAL • p[@justify] •  the value of the attribute doesn’t matter

  6. And others • p[@WIDTH &lt; 40] < 40 (i.e. 2, 35) • p[@WIDTH &gt; 40] > 40 (i.e. 45, 12183) • p[@WIDTH &lt;= 40]  <=40 (i.e. 2, 35, 40) Reminder Some characters have to be escaped in XML because they conflict with the syntax. < &lt; > &gt; & &amp;

  7. Testing elements • “div[p]” Notice the difference with “div/p”

  8. Positions <div> <p>bla bla</p> (1)  just this should be indented <p>bla bla</p> (2) <p>bla bla</p> (3) <p>bla bla</p> (4) </div>

  9. Functions for testing positions • position()  reports on the position of the current node in the current selected list. • last()  tells you the number of the last node in the current selected list.

  10. The XSLT <xsl:template match=“div/p[position()=1]”> <p style=“margin-left: 1cm;”> <xsl:apply-templates/> </p> </xsl:template> <xsl:template match=“div/p[position()!=1]”> <p> <xsl:apply-templates/> </p> </xsl:template>

  11. Abbreviated syntax <xsl:value-of select=“p[position()=1]”/> = <xsl:value-of select=“p[1]”/> • <xsl:value-of select=“p[position()=last()]”/> = • <xsl:value-of select=“p[last()]”/>

  12. Examples and Exercises Example: PBE Exercise: Ex. 3

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