XML-Data: advantages over DTD syntax?

Rick Jelliffe ricko at allette.com.au
Wed Oct 1 13:30:05 BST 1997

> From: len bullard <cbullard at hiwaay.net>
> That said, if it is enabling a more object-oriented capable 
> syntax, then these are two ways to create markup for the 
> same information.  I have no problems with that.  

One difference is also that XML does now include DTD declarations
& PEs.  These will not go away from XML.  So any XML-data software
that is also actually real XML *must* be more complicated than 
XML software that uses just the template method.  So I think the
argument for XML-data to ease the poor programmer's lot is,
to a certain extent, based on a false choice.

The template method may be a little ugly (though to me it is 
less ugly than XML-data, but that is purely a matter of familiarity),
but such ugliness can be dealt with by building nice DTD management

Many of SGML's complications are because it has
so many features to make data entry look nicer, but which do
not improve the expressiveness of the SGML: minimisation,
short-references, datatag, rank, etc.   I tend to think XML-data
is in fact the same kind of thing: it makes some easier to type
but does not improve the expressiveness of XML.   I want to
see things that XML-data can do that SGML cannot now do (I am certainly
not ruling it out--indeed I welcome it, it is an exciting prospect),
either by templates or by architectural forms.  (But, of course, 
I anticipate any great discoveries in this area will find their way
into standard XML/SGML syntax sooner or later.)

All three forms have three stages:

STAGE		templates			AF			XML-data

object	(text template)		Already in		SGML element
primitive					AF system		types

schema 	SGML element types	SGML element	SGML elements
definition					types

schema	SGML elements		SGML elements	XML-data on-the-fly
elements								elements

By the way, I want to also note that the Japanese Hiyama
and Tsuchiya also have an paper on these kind of issues,
which includes an interesting method for restricting possible values
of inherited attributes as well. 

Rick Jelliffe

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