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   Re: Is this invalid?

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  • From: "Steven R. Newcomb" <srn@techno.com>
  • To: ricko@allette.com.au
  • Date: Mon, 22 Mar 1999 11:50:51 -0600

[Rick Jelliffe:]

> From: Didier PH Martin <martind@netfolder.com>
> >Is this markup an invalid XML element?
> >
> ><!AFDR "ISO/IEC 10744:1997">
> > In which document is this listed? I know that these are
> > all valid SGML markup and there is ISO documents on it,
> > but where can I find W3C documents giving that
> > information?

> It is not valid XML. The AFDR markup type was invented to
> signify that the file was *not* SGML or XML. (What a
> strange thing to do: it is the kiss of death. )

Correction: The purpose of the <!AFDR... declaration is to
alert the SGML parser that, in the subsequent DTD, certain
extensions to the syntax of SGML DTDs are used.  These
extensions are standardized in the "Architectural Forms
Definition Requirements" (which a full-fledged ISO standard
in the SGML family of standards: A.3 of ISO/IEC 10744:1997).
Far from being "*not* SGML", it *is* SGML, except in the
technical sense that this extension hasn't yet been
incorporated, officially, in a long-awaited revision of ISO

The <!AFDR... syntax extensions are minor and it's easy (but
redundant) to do without them and still use architectural
forms at full power.  The main extension is that there can
be more than one <!ATTLIST... that contributes attribute
definitions to a single element type.  The other extension
is related to the first: there is a bogus element type
called "#ALL" that can be used in <!ATTLISTs to add
attribute definitions to all element types in the DTD.  This
is merely an easier, more maintainable, and clearer way of
adding "common" attribute definitions to every element.

As for <!AFDR... being the "kiss of death", I couldn't agree
less.  The primary SGML parser in industrial use today is
SP, and SP both recognizes <!AFDR... *and* fully supports
these minor syntax extensions.

Rick is correct in saying that <!AFDR... isn't part of any
W3C Recommendation for XML (at least as far as I know).


Steven R. Newcomb, President, TechnoTeacher, Inc.
srn@techno.com  http://www.techno.com  ftp.techno.com

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