Re: DOCBOOK-APPS: DTD validation question for docbook under redhat

[Jason Diamond <jason at injektilo dot org>]

On Tue, 2002-08-06 at 06:18, Robert P. J. Day wrote:
 
>   i was playing around on the latest red hat beta -- limbo --
> and for the fun of it, decided to see what would happen if i
> tried to define my docbook file with an invalid DTD number, so
> i cranked the value in the public and system identifiers up
> to 4.3, which does not exist -- limbo comes with 4.2.
> 
>   no problem, xsltproc generated the HTML just fine, so i'm
> curious, what's the algorithm for locating the proper DTD when
> xslsproc goes to work?  as i read it, that program uses the
> contents of the env var SGML_CATALOG_FILES, but that still
> doesn't explain why there was no complaint about a non-existent
> DTD file.

I noticed a similar phenomenon recently using TEI. I used xsltproc to
transform a TEI document that referenced the TEI DTD from their website.
The transformation succeeded even though I was currently offline and had
yet to add their DTD to my local catalog. I simply guessed that xsltproc
doesn't do validation and that my document didn't contain any entity
references that needed to be replaced (or maybe it did but just silently
skipped them).

By the way, I believe that libxml uses /etc/xml/catalog for its XML
catalogs. You can override this by setting $XML_CATALOG_FILES. The
--help output for xmllint says that $SGML_CATALOG_FILES is only used
when you specify --catalogs. libxml must have support for the older SGML
catalog specification that's not enabled by default.

Jason