# [NTG-context] Xml filtering in Lua

Thomas A. Schmitz thomas.schmitz at uni-bonn.de
Wed Nov 16 18:33:07 CET 2022

Hi Duncan,

Thank you for pointing this out! I knew this was true inside the xmlns namespace, so you can’t have identical xml:id tags, but you’re probably right that it’s better to avoid this confusion altogether. Alas, this doesn’t help with my problem. Since there was a type in my minimal example from my experimentations, I include a corrected version, avoiding the identical tags

All best

Thomas

\startbuffer[test]
<document>
<topics>
<topic t:id="test1">
<title>This is the first test</title>
<date>22/11/16</date>
</topic>
<topic t:id="test2">
<title>This is the second test</title>
<date>22/11/17</date>
</topic>
</topics>
<chapters>
<chapter ch:id="test1">
<content>
This will be the content of the <emph>first</emph> chapter.
</content>
</chapter>
<chapter ch:id="test2">
<content>
This will be the content of the <emph>second</emph> chapter.
</content>
</chapter>
</chapters>
</document>
\stopbuffer

\startxmlsetups xml:testsetups
\xmlsetsetup{#1}{*}{-}
\xmlsetsetup{#1}{document|chapters|chapter|content|emph}{xml:*}
\stopxmlsetups

\xmlregistersetup{xml:testsetups}

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

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

\startxmlsetups xml:chapter
\xmlfunction {#1} {chapter}
\xmlflush {#1}
\stopxmlsetups

\startxmlsetups xml:chapter:content
\xmltext {#1} {content}
\stopxmlsetups

\startxmlsetups xml:emph
{\em \xmlflush {#1}}
\stopxmlsetups

\startluacode
function xml.functions.chapter (t)
local ch_id = t.at.ch:id
local metadata = xml.filter (t, '../../topics/topic[@t:id=="%s"]', ch_id)
lxml.command(t, ".", "xml:chapter:content")
context.par ()
context (ch_id)
context.par ()
end
\stopluacode

> On 16. Nov 2022, at 17:18, Duncan Hothersall via ntg-context <ntg-context at ntg.nl> wrote:
>
> I'm not sure about the code, sorry, but I do know that an XML document can't have two IDs of the same value. Typically you would use a linkend attribute on the element which is referencing an id (in this case the topics, I think).
>
> Probably doesn't help with your problem, but it's likely a prerequisite for it to work.
>
> Bests,
>
> Duncan