title: Not IN equivalent in XPath expression
body: <p>I am working on an XSL development and I am in need of knowing the NOT IN equivalent in XPATH. 
  I am presenting the XML and XSL in the simplest format which would be understandable to all.</p>
  
  <pre><code>&lt;?xml-stylesheet type="text/xsl" href="XSL.xsl"?&gt;
  &lt;Message&gt;
      &lt;Customers&gt;
          &lt;Customer pin="06067"&gt;1&lt;/Customer&gt;
          &lt;Customer pin="06068"&gt;2&lt;/Customer&gt;
          &lt;Customer pin="06069"&gt;3&lt;/Customer&gt;
          &lt;Customer pin="06070"&gt;4&lt;/Customer&gt;
          &lt;Customer pin="06072"&gt;5&lt;/Customer&gt;
      &lt;/Customers&gt;
      &lt;Addresses&gt;
          &lt;Address pin1="06067"&gt;A&lt;/Address&gt;
          &lt;Address pin1="06068"&gt;B&lt;/Address&gt;
          &lt;Address pin1="06069"&gt;C&lt;/Address&gt;
      &lt;/Addresses&gt;
  &lt;/Message&gt;
  </code></pre>
  
  <p>XSL</p>
  
  
  
  <p></p>
  
  <pre><code>&lt;xsl:template match="/Message"&gt;
      &lt;html&gt;
          &lt;body&gt;
              &lt;h4&gt;Existing Customers&lt;/h4&gt;
              &lt;table&gt;
                  &lt;xsl:apply-templates select="//Customers/Customer[@pin = //Addresses/Address/@pin1]"&gt;&lt;/xsl:apply-templates&gt;
              &lt;/table&gt;
  
              &lt;h4&gt;New Customers&lt;/h4&gt;
              &lt;table&gt;
                  &lt;!--This place need to be filled with new customers--&gt;
              &lt;/table&gt;
          &lt;/body&gt;
      &lt;/html&gt;
  &lt;/xsl:template&gt;
  
  &lt;xsl:template match="Customer" name="Customer"&gt;
      &lt;xsl:variable name="pin" select="./@pin"&gt;&lt;/xsl:variable&gt;
      &lt;tr&gt;
          &lt;td&gt;
              &lt;xsl:value-of select="."/&gt;
              &lt;xsl:text&gt; is in &lt;/xsl:text&gt;
              &lt;xsl:value-of select="//Addresses/Address[@pin1=$pin]"/&gt;
          &lt;/td&gt;
      &lt;/tr&gt;
  &lt;/xsl:template&gt;
  </code></pre>
  
  <p></p>
  
  <p>In the above XSLT, under the commented area, i need to match and display the customers who's address is not existing in the Addresses/Address node.</p>
  
  <p>Please help find an XPath expression that would match the Customers who are NOT IN the Addresses Node set. (Any alternate could also help)</p>