DOCBOOK-APPS: Re: SGML vs XML

[Yann Dirson <ydirson at users dot sourceforge dot net>]

On Tue, Jul 30, 2002 at 03:31:19PM -0700, Norman Walsh wrote:
> / Yann Dirson <ydirson@users.sourceforge.net> was heard to say:
> |> The proposed linking extensions will add XLink-namespaced attributes
> |> more-or-less throughout. That works fine in SGML, until someone uses a
> |> different xmlns declaration for the XLink namespace in different parts
> |> of the same document.
> |
> | Why should it be a problem ?  That's something an XML author could
> | want to do, but that would just not be available to SGML authors.  Or
> | do I miss the point ?
> 
> I didn't speak clearly. The issue isn't really SGML vs XML here, it's
> DTD validation.
> 
> You can't make this work:
> 
>   <section>...
>     <para xmlns:xlink="...">
>       <emphasis xlink:href="...">...</emphasis>
>     </para>
>     <para xmlns:xl="...">
>       <emphasis xl:href="...">...</emphasis>
>     </para>
>   </section>
> 
> You can make either prefix (xl: or xlink:) work in any given document,
> but as soon as you mix them, DTD validation is out the window.

Sure.  But that'd only be possible in a namespace-enabled XML
environement.  For SGML we anyway have to select a "namespace prefix",
hardcode it in the DTD, and stick with it.

I can see no place for using different prefixes, unless we define the
prefix as a general entity, AND use SUBDOCs in which we'll define this
entity to different values.  But anyway SUBDOCs are not used by
DocBook, so that applies only to customisation layers that use them.

Regards,
-- 
Yann Dirson <Yann.Dirson@fr.alcove.com>                 http://www.alcove.com/
Technical support manager                Responsable de l'assistance technique
Senior Free-Software Consultant          Consultant senior en Logiciels Libres
Debian developer (dirson@debian.org)                        Développeur Debian