xml cross-references in lua?

["Thomas A. Schmitz" <thomas.schmitz@uni-bonn.de>]

Hi all,

I have a question about xml processing and I think that what I want/need 
can best be achieved by using lua code, but so far, I'm not really sure 
how to proceed, so any help from one of the resident lua gurus would be 
welcome.

So: the question. xml allows to provide elements with unique identifiers 
so that one can add cross-references within the document structure. Here 
is a sample xml file that shows what I mean:

<document>
   <bibitem xml:id="hagen2011">
     <author>Hans Hagen</author>
     <title>The Meaning of Life Is 42</title>
     <journal>The Rhetoric of Mathematics</journal>
     <date>2011</date>
   </bibitem>
   <bibitem xml:id="hagen2012">
     <author>Hans Hagen</author>
     <title>The New Meaning is Now 43</title>
     <journal>High Energy Metaphysics</journal>
     <date>2012</date>
   </bibitem>
   <text>
     <p>This has been successfully proven in papers by <bib
     ref="#hagen2011"/> and <bib ref="#hagen2012"/>.</p>
   </text>
</document>

[Note: the TEI guidelines add the hash character in the attribute value 
to such references, but after much googling, I'm still not sure if this 
is standard or necessary or bizarre.]

So: at the point of the reference (which may be empty, like here, or 
contain text), I want to refer back to the bibitems. The typesetting 
engine should then be instructed to pick up the information, so that 
this is, e.g., typeset as "This has been successfully proven in papers 
by Hans Hagen (2011) and Hans Hagen (2012)."

My idea: since the xml:id attributes must be unique across the document, 
it would be easiest to collect them into a lua table, with the xml:id as 
key, so their content could be accessed and typeset later. But 
unfortunately, I have no clue how to go about this... Could somebody 
provide a pointer?

Thanks for your interest, if you've read this far!

Thomas
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