> I can sort the elements from both the documents in ascending 
> or descending order and extract the maximum and minimum value 
> elements using a single stylesheet. But how do I perform 
> mathematical operations on the sorted elements ? For e.g if I 
> want to add the first and the last <From> element from the 
> sorted list of <From> elements how can I do this and store 
> this value in a global variable so that it can be reused ? 
> 

You capture the sorted lists in result tree fragments and then use the
xx:node-set() extension function to access these as if they were source
documents:

<xsl:variable name="sorted-list-1">
  <xsl:for-each select="document('a.xml')/record">
    <xsl:sort select="key"/>
    <xsl:copy-of select="."/>
  </
</

<xsl:variable name="sorted-list-2">
  .. ditto ..
</

<xsl:variable name="sum-of-first-and-last"
   select="xx:node-set($sorted-list-1)/record[1] +
           xx:node-set($sorted-list-1)/record[last()]"/>

Michael Kay
Software AG
home: Michael.H.Kay@xxxxxxxxxxxx
work: Michael.Kay@xxxxxxxxxxxxxx 


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