XML/XSLT stylesheet/intersect

intersect operator

File: Data.xml
<?xml version="1.0" encoding="utf-8"?>
<favorite-books>
  <booklist>
    <book isbn="1111111111" 
      favorite="f1">XSLT</book>
    <book isbn="2222222222" 
      favorite="Doug">Java</book>
    <book isbn="3333333333" 
      favorite="Doug">C++</book>
    <book isbn="4444444444" 
      favorite="f1">SQL</book>
    <book isbn="5555555555" 
      favorite="Sheri">Oracle</book>
    <book isbn="0375724443" 
      favorite="Sheri">Java</book>
  </booklist>
</favorite-books>

File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="2.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  
  <xsl:output method="text"/>
 
  <xsl:variable name="Dougs-favorites" as="node()*">
    <xsl:sequence 
      select="/favorite-books/booklist
              /book[contains(@favorite, "Doug")]"/>
  </xsl:variable>
  <xsl:variable name="Sheris-favorites" as="node()*">
    <xsl:sequence 
      select="/favorite-books/booklist
              /book[contains(@favorite, "Sheri")]"/>
  </xsl:variable>
  <xsl:template match="/">
    <xsl:text>&#xA;Books we both like:</xsl:text>
    <xsl:text>&#xA;&#xA;  </xsl:text>
    <xsl:for-each select="$Dougs-favorites intersect $Sheris-favorites">
      <xsl:sort select="."/>
      <xsl:value-of select="."/>
      <xsl:text>&#xA;  </xsl:text>
    </xsl:for-each>
  </xsl:template>
</xsl:stylesheet>
Output:

Books we both like: