SGML SEEALSO Parameter

[Arjun Ray <arayq2@gmail.com>]

 On Wed, 21 Jul 2021 15:09:20 -0400, John Cowan <johnwcowan@gmail.com>
wrote:
| On Wed, Jul 21, 2021 at 12:30 AM Rick Jelliffe <rjelliffe@allette.com.au>
| wrote:

| > 3. The language *MUST NOT* be characterizable by WebSGML (ISO SGML as
| > extended, e.g. by Annex J and K) without the use of the SEEALSO capability.
| 
| Alas, I am not an SGML maven, so I can't interpret that without much
| research.

The SEEALSO parameter in the SGML Declaration was itself invented in
the WebSGML TC, I believe:

    http://www.sgmlsource.com/8879/n0029.htm

It isn't documented well at all, so the details and nuances are known
only to the people present at the creation.  The general idea seems to
be that it's a reference to another spec of some kind that documents
constraints not expressible in SGML.  (Though how that differs from
APPINFO is somewhat of a mystery too.)

All kind of vague, no doubt.

Rick may be getting at the idea that this new generation XML may not
even be a SGML "profile", and that therefore, inter alia, we should
not expect a conforming SGMl parser, even with modifications, to be
able to parse all new doucments.  Presaging a final break with SGML?
Just a guess.