J.Fine wrote:
>> Fundamental point, of course, but the current plan is that LaTeX3 will
>> work with pdfTeX, XeTeX and LuaTeX. If we were going down the ConTeXt
>> "LuaTeX-only" route, then I'd quite possibly agree. But we're not (at
>> the moment!).
> 
> You're claiming here that there is a requirement here to use TeX macros, namely use with pdfTeX etc.  But what you say does not impose such a requirement.
> 
> Don Knuth's WEB system uses a custom program WEAVE to create a TeX input file from a .web file.
> 
> It's perfectly possible to use a similar front end for processing documents written in the LaTeX syntax.

My impression is that we are *not* in the business of writing any new
binaries. The team have always tried to leave that to the "engine
people". You can of course argue that it might be better to take a
different approach, but I think if you do then the LuaTeX-only route
looks the most sensible (at the tool is there and being actively improved).

> Surely to do this you will need a LaTeX->XML translator written in /some other language/.  And once you have that, why do you need an implementation written in TeX macros?
> 
> And come to that, the translator will surely want access to
>>> \DeclareDocumentCommand \section { s o m } {
>>>   % Code here
>>> }
> ===
> 
> Any comments here?

I'm not sure how everyone sees this. My take is that xparse is mainly
about <arbitary input> => LaTeX-as-typesetting-system. So, for example,
to read XML you re-do your document commands but leave the underlying
code functions alone.

One thing you could consider is:

LaTeX-document-syntax => XML (or other structured format) =>
LaTeX-as-typesetting-system

i.e. always doing some kind of translation to a very structured format.
 Other people on the team are the experts on this type of idea: I can
see that TeX macros would not necessarily be a good choice. (That said,
ConTeXt has a lot of XML stuff going on, even in Mk II, and I'm not sure
how much TeX is used there.) My worry with this approach is that you
will exclude so many people from using it that you'll never get anywhere
in user terms.
-- 
Joseph Wright