Namespaces, Architectural Forms, and Sub-Documents

Eve L. Maler elm at
Thu Feb 5 00:16:44 GMT 1998

This exchange is fascinating.  One comment:

At 05:53 PM 2/4/98 -0500, David Megginson wrote:
>Paul Prescod writes:
> >  * "content model communication" (how do I pass a %cell; content model
> > into my table subdoc)
>You're thinking of CALS here.  I'd suggest that we move away from the
>older SGML model of heavily parameterised DTDs (as from heavily
>#IFDEF'ed C header files): remember that one of the arguments for the
>namespace model is to reuse stylesheets and other processing
>specifications -- if a table model can vary its content unpredictably,
>then you will not be able to reuse stylesheets anyway.  Again,
>encapsulation is a big win, and it keeps things easy.

I don't think the problem has anything to do with CALS.  In fact, until
SGML Open came along, it was pretty hard to use the CALS table model as a
module -- it was not designed with this use in mind, and its inflexibility
resulted in dozens or hundreds of DTDs recoding the whole thing just to
change a few features.

Table models, even if they're not CALS, are going to vary their content
unpredictably, because cells typically need to contain markup *inside* them
that is specific to the information domain *outside* the table structure;
they're surrounded coming and going.  (As an aside, I don't think this
means you can't reuse stylesheets; you just sequester the table geometry
stuff from the cell formatting and recode just a little bit of
element-in-context stylesheet code.)

Table cells are a common boundary case of namespace mixing from the text
world, and perhaps there are similar situations in the data world.  I think
that a black-box approach (subdocuments) would require way more overhead
than a unified-model approach in doing "content model communication."


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