Re: xml cross-references in lua?

[Hans Hagen <pragma@wxs.nl>]

On 11-9-2012 19:22, Thomas A. Schmitz wrote:
> 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!

If the number of bib items is not that large hashing does not save much. 
(In x-xfdf.mkiv you can see another example).

\starttext

\startbuffer[demo]
<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>
\stopbuffer

\startxmlsetups xml:define
     \xmlsetsetup{#1}{*}{xml:*}
\stopxmlsetups

\startxmlsetups xml:document
     \xmlall{#1}{/text}
\stopxmlsetups
\startxmlsetups xml:text
     \xmlflush{#1}
\stopxmlsetups
\startxmlsetups xml:p
     \xmlflush{#1}
     \par
\stopxmlsetups

\startxmlsetups xml:bib
    \BibAuthor{#1}{\xmlatt{#1}{ref}}
\stopxmlsetups

\startxmlsetups xml:author
     [[\xmlflush{#1}]]
\stopxmlsetups

\def\BibAuthor#1#2{[1:\xmlfirst{whatever}{/document/bibitem[@xml:id==string.sub('#2',2)]/author}]}

\xmlregistersetup{xml:define}

\xmlprocessbuffer{whatever}{demo}{}

\startluacode
     userdata = userdata or { }
     userdata.bibitems = { }
\stopluacode

\startxmlsetups xml:document
     \xmlflush{#1}
\stopxmlsetups

\startxmlsetups xml:bibitem
     \ctxlua{userdata.bibitems["\letterhash\xmlatt{#1}{xml:id}"] = "#1"}
\stopxmlsetups

\def\BibAuthor#1#2{[2:\xmlfirst{\cldcontext{userdata.bibitems['#2']}}{/author}]}

\xmlprocessbuffer{whatever}{demo}{}

\stoptext

(I ran into a recently introduced side effect of an optimization so I'll 
generate you a new beta. Older versions should work anyway as no special 
trickery is used.)

Hans


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