Performing Set Operations When Querying XML - Implementing the Recursive Templates

These recursive templates are implemented in terms of the following definitions:

Union(nodes1,nodes2)
   The union includes everything innodes2plus
   everything innodes1not already a member of  
   nodes2.

Intersection(nodes1,nodes2)
   The intersection includes everything innodes1that 
   is also a member ofnodes2.

Difference(nodes1,nodes2)
   The difference includes everything innodes1that is
   not also a member ofnodes2.

In all cases, membership defaults to equality of string values, but the importing stylesheet can override this default.

Given these value-oriented set operations, you can achieve the desired effect on people1.xml and people2.xml using the following stylesheet:

  <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/ Transform"
   xmlns:vset="http:/www.ora.com/ XSLTCookbook/namespaces/vset">

  <xsl:import href="set.ops.xslt"/>

  <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>

  <xsl:template match="/">
    <people>
      <xsl:call-template name="vset:union">
        <xsl:with-param name="nodes1" select="//person"/>
        <xsl:with-param name="nodes2" select="document('people2.xml')//person"/>
      </xsl:call-template>
    </people>
  </xsl:template>

  <!--Define person equality as having the same name -->
  <xsl:template match="person" mode="vset:element-equality">
    <xsl:param name="other"/>
    <xsl:if test="@name = $other/@name">
      <xsl:value-of select="true()"/>
    </xsl:if>
  </xsl:template>

  </xsl:stylesheet>

Next: XSLT 2.0 Enhancements >>
 

More XML Tutorials Articles
More By O'Reilly Media