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Re: Syntax + object model

• To: xml-dev@l...
• Subject: Re: Syntax + object model
• From: "Simon St.Laurent" <simonstl@s...>
• Date: Sat, 24 May 2003 22:31:42 -0400
• In-reply-to: <hl80dvgn94sg20nu7q92j6e6cjov17bjji@4...>

aray@n... (Arjun Ray) writes:
>| DTDs emerge from an understanding of what markup does, but both do
>| too much (infoset augmentation)
>
>Well, that's if one assumes there is a "the infoset" to be so
>augmented.

Fair enough.  I'm using a more recent term to describe the actions of
something that existed long before, and it reeks of anachronism.

>I think John Cowan once clarified that the Infoset Rec actually
>specifies only "an infoset", and not in any way "the infoset" in some
>normatively exclusive sense (though "derivative" specs of late seem
>quite eager to treat it so).

John is wisely modest about the Infoset.  I'm very glad that work wasn't
done by, uh, more eager people.

>| and too little (modularization is an interesting challenge.) 
>
>Actually, that isn't a problem with DTDs as much as it's a problem
>with the (implicit) validation model.  That is, if you assume that a
>DTD will be comprehensive about a document (an "encompassing
>architecture" to the HyTime folks) then modularization is a definite
>challenge.  Of course, DTDs were originally developed with
>comprehensiveness in mind only, but it's possible to relax the default
>scope and apply particular DTDs to only parts of a document (as in
>"enabling architectures").  For example, RNG can take a "maximal fit"
>rather than a "complete fit" view of validation. Similarly, it's
>possible to assume the moral equivalent of (#DONTCARE) as the content
>model of some elements, and thus delegate subtree validation
>constraints to other DTDs. 

I think this is a more complicated field.  Modularization always is, and
I was shocked to see the what lurks behind the TEI Pizza Chef.  Working
with DocBook (to take the example I deal with most frequently) is
simpler, but it can still be fun to wander through the parameter
entities, even in my employer's semi-simplified version.  

Generally speaking, I'm happier working with RELAX NG at this point than
with DTDs, but I still use (and even sometimes enjoy) DTDs on a regular
basis.

>That said, *XML* DTDs are utterly crippled in relation to SGML DTDs,
>and even those lack expressive power in some areas.   

I've only read SGML DTDs, never created them, so I'm definitely not
qualified to comment.

>| [...] while DTDs do too little, and extending them requires a lot of
>|ad hoc work.
>
>If you mean things like PE games to shoehorn colonified names, that's a
>colossal waste of time and energy indeed.

That's a particular case of perverse brilliance.  I'm amazed that the
loopholes for making it work proved usable, but it's no fun to work
through loopholes.

-- 
Simon St.Laurent
Ring around the content, a pocket full of brackets
Errors, errors, all fall down!
http://simonstl.com -- http://monasticxml.org

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