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   Re: A Line in the Declarative Syntax Sand(Was: XML complexity,namespaces

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  • From: Paul Prescod <paul@prescod.net>
  • Date: Wed, 24 Mar 1999 11:00:40 -0600

David Megginson wrote:
> Sean Mc Grath writes:
>  > This is an interesting thread.  Many non-tag-minimization
>  > reliables can be put forth as things that SGML "can do" that
>  > XML cannot. Things like data attributes, exclusion exceptions,
>  > internal SDATA entities and so on.
> I think that I agree with what Sean is saying here and later in the
> message -- think of *what* you can represent rather than *how* you
> represent it.

That representation alone isn't good enough -- standardization is also

Here's what I heard Sean saying:

 * SGML favours globally standardized declarations over locally maintained
custom code.

 * XML restricts the number of globally standardized declarations in favor
of locally maintained custom code.

In other words: SGML favours standarization and XML favours one-off
system-specific ad-hocery. If I really believed that then I would drop XML
and advise my customers not to use it. XML removed certain specific
declarative features of SGML that were either not used enough or could be
added in at another level. But little by little XML is becoming more and
ore declarative through other layers like XLink, XSL, RDF and XML Schemas.
The move towards declarativeness and away from ad hoc code is precisely
XML's gift to the Web. Standardized declarativeness is the real XML
revolution. XML just happens to be the syntax.

Let me demonstrate that XML is also standard declaration-focused by
turning around the "notations" example. The SGML way was to declare a
notation and have a second level validate that the data adhered to the
notation. Unfortunately, we never really standardized a decent declarative
syntax for the second level. In other words, SGML was not declarative

XML, on the other hand, will likely have a mechanism where notations can
be declared in the schema (under the title of "user-defined data types").
So the XML family will have a more powerful, standardized, declarative
mechanism which will reduce the need for maintaining custom code. The
declarativeness baton has been passed from SGML to XML.

Custom code is the enemy. We will always need it but we must continue to
relegate it to more and more complex or esoteric problems.

 Paul Prescod  - ISOGEN Consulting Engineer speaking for only himself

"Perpetually obsolescing and thus losing all data and programs every 10
years (the current pattern) is no way to run an information economy or
a civilization." - Stewart Brand, founder of the Whole Earth Catalog

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