Re: XML catalog draft

When PUBLIC and SySTEM are both given, writes Murray Altheim,
> [first look at the SYSTEM Identifier] Then,
> if the SYSTEM fails, resort to the more generalized process of a catalog
> lookup using PUBLIC.
> I believe Panorama has the same behaviour.


If you give a SYSTEM Identifier, Panorma looks only at that, and ignores
the PUBLIC identifier for the purposes of fetching the DTD.  The PUBLIC
ID is still used as a lookup key in ENTITYRC for navigator definitions
and stylesheets.  If the SYSTEM ID doesn't work, Panorama gives up.

Probably all ViewPort applications are the same, although it's possible
in theory for a VP application to change this behaviour.

Author/Editor is the same: if the SYSTEM ID is given and doesn't
work, the user is asked to specify a "rules file" (the compled DTD)
in a pop-up file finder dialogue box.

If you treat the SYSTEM ID is being the thing that tells you how to
resolve the PUBLIC ID, this is the only approach possible.  If the
author has specified how to find the DTD, we shouldn't use another one.

The whole problem with PUBLIC is that different people use it for
different things, and the standard gives no clear guidance.

I still think we should avoid PUBLIC.  I have yet to see any clear examples
that require it.  Paul Prescod has come close, with a teaching environment
using SGML where the students don't have network access, but it is not
clear to me that that example applies to a version of SGML developed
especially for web use.  In other words, the requests for PUBLIC seem
to come from SGML users rather than Web users, and stem largely from
backwards compatibility.  Jon's system at Sun is interesting, but
could equally well be done with URLs as far as I can see.