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   Re: [xml-dev] Come On, DTD, Come On! Thoughts on DSDL Part 9

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Marcus Carr <mcarr@allette.com.au> wrote:

| Are we really certain that there will never be a mechanism similar to 

Never say never. :-)

If OMITTAG ever makes into XML, it ought not to be SGML's broken variant.

One use that I'd like to have (in SGML too) is a "virtual element type"
whose basic purpose is grouping, allowing a complex content model to be
analysed into simpler named components.  For instance, suppose we had a
HTML-like specification like this:

  <!ELEMENT  dl  (dt+,dd+)* >

Sometimes it's useful to gather a term with its descriptions as a group,
like this:

  <!ELEMENT  dl  (dli)* >

  <!MODEL  dli  (dt+,dd+) >

Such "elements" could be required to have no tags!  (And they also take
away one reason to use parameter entities.  An open issue would be whether
such virtual elements should share the same namespace as element types, or
be indicated specially in model groups with a distinct marker, such as a
'$' or '@' prefix.) 

| A year ago I would have bet that nobody would ever put any further work 
| into DTDs, yet here we are. 

I've never understood the distaste for DTDs.  The only real eyesore is
parameter entities.  They function as grabbags for all the things that
were missed in the first cut at the syntax - too few kinds of declarations
and thus the brittle practice of using a text substitution mechanism to
"capture" conceptual categories.


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