The history of luaTEX 2006–2009 / v 0.50 - Pragma ADE

This will save the content of the author element and ush it when the end tag article is
seen. So, given previous denitions, we will get the title, some text and then the author.
You may argue that instead we should use for instance xslt but even then a mapping is
needed from the xml to TEX, and it's a matter of taste where the burden is put.
Because ConTEXt also wants to support standards like MathML, there are some more
mechanisms but these are hidden from the user. And although these do a good job in
most cases, the code associated with the solutions has never been satisfying.
Supporting xml this way is doable, and ConTEXt has used this method for many years in
fairly complex situations. However, now that we have Lua available, it is possible to see
if some things can be done simpler (or differently).
After some experimenting I decided to write a full blown xml parser in Lua, but contrary to
the stream based approach, this time the whole tree is loaded in memory. Although this
uses more memory than a streaming solution, in practice the difference is not signicant
because often in MkII we also needed to store whole chunks.
Loading xml les in memory is real fast and once it is done we can have access to the
elements in a way similar to xpath. We can selectively pipe data to TEX and manipulate
content using TEX or Lua. In most cases this is faster than the stream-based method. Interesting
is that we can do this without linking to existing xml libraries, and as a result we
are pretty independent.
So how does this look from the perspective of the user? Say that we have the simple
article denition stored in demo.xml.
Whatever
Someone
some text
This time we associate so called setups with the elements. Each element can have its own
setup, and we can use expressions to assign them. Here we have just one such setup:
\startxmlsetups xml:document
\xmlsetsetup{main}{article}{xml:article}
\stopxmlsetups
When loading the document it will automatically be associated with the tag main. The
previous rule associates setup xml:article with the article element in tree main.
We need to register this setup so that it will be applied to the document after loading:
\xmlregistersetup{xml:document}
The luaTEX Mix 209