#7 XML catalog support

[Michael(tm) Smith]

XML catalogs[1] seem to be the XML evolution of
SGML/OASIS Open
catalogs. Daniel Veillard has already implemented them
in Libxml2[2]
and in his xmllint application.

I think it'd be real useful to have support for XML
catalogs in PSGML,
and it seems like it'd not be nearly as much work to
implement as some
of the other new PSGML features that folks have been
requesting (XML
schema support, for example).

[1] http://www.oasis-
open.org/committees/entity/spec.html
[2] http://xmlsoft.org

[Sagar R. Shah]

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Please please please please please could we have XML Catalog
Support

[James Henstridge]

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I did a quick hack to add xml catalog support to psgml,
which you can find here:
http://www.daa.com.au/~james/files/xmlcatalog.el

(it isn't finished yet, but should work a bit). It calls
the xmlcatalog program (distributed with libxml2) to
perform the catalog lookups.

It was able to load up the DTD for a DocBook document using
the following doctype:

<!DOCTYPE article SYSTEM
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">

[Michael(tm) Smith]

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Very cool. I had my XML catalog file set up only
with public IDs, but added system IDs and
PSGML found everything as expected.

James - Are you planning on implementing support
for public IDs?

[James Henstridge]

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The hook used by that bit of elisp uses is to perform
lookups of unknown system identifiers, so no, I probably
won't be expanding it to do that (I don't know that much elisp).

The other drawback is that it doesn't handle relative sysids
very well. For example, the modulare XHTML 1.0 DTD includes
the latin1 entities with the relative sysid of
"xhtml-lat1.ent", and that gets passed straight through to
my hook, without any context needed to resolve it.