Using a reference in a sort

I am trying to sort data based on an externally referred to value.  My
main XML file looks like this:

    <task>
      <person id="p001">
        ...
      </person>
    </task>

p001 refers to a person in another file structured like this:

    <people>
      <person id="p001" last="Heines" first="Jesse">
        ...
      </person>
    </people>

I can get at that person's last name by defining a variable to point to
the file:

    <xsl:variable name="filePeople" select="string('people.xml')" />

and then using that variable inside a template using an xsl:value-of:

  <xsl:value-of
select="document($filePeople)/people/person[@id=$strPersonID]/@last" />

(where $strPersonID is the ID extracted from the main XML file).

What I can't seem to be able to do is sort using this field.

    <xsl:apply-templates select="tasks/task">
      <xsl:sort 
 
select="document($filePeople)/people/person[@id=$strPersonID]/@last" 
          order="descending" />
    </xsl:apply-templates>

The problem is that one must use variables due to the context node
switching in this long XPath statement, but XSL won't let me use
xsl:variable inside an xsl:apply-templates statement.  The variable must
be defined inside the xsl:apply-templates tag so that it changes with
each recursion.

I tried using xsl:for-each, which does allow xsl:variable inside it, but
only *after* xsl:sort, so that doesn't work either.

I would appreciate any suggestions anyone can make to address these
issues.

Thank you,
Jesse Heines, heines@xxxxxxxxxx
UMass Lowell Computer Science




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