draft-whitehead-mime-xml-04

Paul Prescod papresco at technologist.com
Mon Jun 8 18:35:12 BST 1998


On Tue, 9 Jun 1998, MURATA Makoto wrote:
> An external parameter entity can also be an external DTD subset.  
> Thus, "dtd" and "entity" should not be distinguished, as I see it.  The only 
> reasonable thing is to distinguish "dtd" (including parameter 
> entities) and "entity" (including document entities).

XML does not define a concept of "DTD" that can stand alone separate from
an XML document. The closest you could come is "set of markup declarations."
But all "sets of markup declarations" can be used as entities.

The idea that "sets of markup declarations" are really "DTDs" is one of the
most pernicious misunderstandings in SGML and XML processing. I think Eliot
calls it one of the 10 big lies.

This is one reason that XSchemas are not merely another syntax for 
"DTDs". They are a new schema language entirely. Any resembelance to DTDs 
is merely due to the fact that they have similar goals (document validation).

 Paul Prescod


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