Muenchian grouping on external XML files

Is there any way I can use keys when calling on external XML files using
the document function? I am trying to use the Muenchian grouping
technique to list unique content values for an element, but the values
exist in a document that is external to the one I'm processing.

More detail below (apologies for long post):

I am developing an application that publishes XML files (marked up in
TEI) as static HTML files. I am processing one set of XML files which
create the general web pages themselves, e.g. snippet from 'genweb.xml'

-----------------XML FILE--------------
<TEI.2>
  ...
  <text>
    ...
     <p>This is an index of people:</p>
     <divGen id="personIndex" />
     <p>And some more text ...</p>
  </text>
</TEI.2>
-------------------------------

My TEI publishing process uses the <divGen> element in this XML file to
call for an index to be created at a particular point: in this case, an
index of people.

I have another series of (primary source) XML files that contains
various references to people. Snippet2 from an example 'primary.xml':

-----------------XML FILE--------------
<TEI.2>
  ...
  <text>
    ...
     <p>Some text with mentions of <rs type="person">person 1</rs> and
<rs type="person">person 2</rs>.</p>
     <p>And some more text ...</p>
     <p>Another mention of <rs type="person">person 1</rs></p>
  </text>
</TEI.2>
-------------------------------

I group these primary source files together as a collection in
'master_primary.xml'. I then want to create an index of people mentioned
throughout the collection, with links to the individual mention.
Something like this:

-----------------HTML output--------------
Index of people mentioned

[each asterisk takes you to an individual mention of the person in
question]

person 1:  *  *  *
person 2:  *  *  *  *  *
-------------------------------

I normally do this with Muenchian grouping, but can't get it working on
external XML files. See following XSLT snippet, which I think crashes
because of the match pattern in <xsl:key>:

-----------------XSLT FILE--------------
<xsl:key name="myKeyName" match="document('master_primary.xml')//rs"
use="normalize-space(.)" />
 
<xsl:template match="divGen">
  <xsl:if test="@id='personIndex'">
    <xsl:for-each
select="document('../../xml/02_master/master_object.xml')//rs[generate-i
d(.)=generate-id(key('myKeyName',
normalize-space(.))[1])][@type='person']">
                   NOW DO SOMETHING ELSE ...
    </xsl:for-each>
  </xsl:if>
</xsl:template>
---------------------------------------------

I can think of other methods, using intermediate XML output, but would
prefer to avoid them if possible.

I am using Saxon processor version 6.5.2.

Thanks in advance,
Paul

---------------------------------------
Paul Spence
Centre for Computing in the Humanities
King's College London


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