Re: DOCBOOK-APPS: Re: conditionalization of XML

["Eric S. Raymond" <esr@thyrsus.com>]

Daniel Veillard <veillard@redhat.com>:
> > You know, there's reason people keep re-inventing mechanisms for this.
> > It's because they need to get work done -- and getting work done often 
> > means wanting to conditionalize documents without spending days on some
> > elaborate custom XSLT hack.
> 
>   But then you put the burden on someone else. And an underspecified,
> underreviewed mechanism is the hell of the maintainer's

Do we build tools to be worshiped or to be used?  It's our *job* to accept
that `burden', Daniel.

The conditionalization mechanisms now available are complex, weak, and
painful to use.  This needs to be fixed.  I have made a start at addressing
the problem.  I don't pretend to have a final solution, but at least I'm
doing something more effective than chanting the sacred litanies of XML 
theology and how XSLT will save us all, hallelujah!  

It would be nice if somebody else would notice that this is a real-world 
problem that affects real users.  I bumped my nose on it because I'm working
with a real document, the Jargon File.  You might have heard of it.

>  Doesn't cover a hell of issues, 2mn read just pops up tons of unspecified
> behaviour or serious problems. Heck, even the "condition=" syntax is only
> given in the example ....

"condition" could be any attribute.  The tool doesn't care.
 
> - well formedness breakage, your description is done at the
>   serialization level, it has 0 garantee on the level of XML well-formedness

That's right.

>   <?if condition='html'?>
>   <foo>
>   <?elif condition='pdf|ps'?>
>   </foo>
>   <?fi?>
> 
>   What gives ??? A further XML well formedness error ? In that case it's
>   better left external. Otherwise you'd have to start to give a description
>   in terms of the infoset, or similar like XInclude does.
> 
> - malformed preprocessor commands
>     <?if?>
>     <?elif cond='pdf
>     |foo'?>
>   unlatched <?else?> or <?fi?>, etc, etc ...

If you do this, you lose :-).

>   what is handled, and how ?

xmlif knows nothing about the XML structure of the document.  All it `sees'
is the processing instructions what is otherwise, from its point of view,
a featureless byte stream.
-- 
		<a href="http://www.tuxedo.org/~esr/";>Eric S. Raymond</a>