XCatalogs & Stylesheets (was Re: NMU request: docbook-xml bug fixes)

[Mark Johnson <mrj@debian.org>]

On , June 25, Michael Alan Dorman wrote:
> 
> This may be a stupidly naive question (AKA, one that is documented
> somewhere), but how would one use a catalog entry to specify a
> stylesheet?

Not naive at all, Mike. More like a direct hit to one of the central
issues in XML/XSL. And once again, Norm Walsh and OASIS have come to
the rescue. But there's no implementation at present, this stuff is
still in the draft stage.

Here's my limited understanding...

Short, possibly incorrect, answer:

   Someone assigns a URN [1] in the "publicid" namespace [2] to their
   stylesheet distribution. 

     Fictitous example: "urn:publicid:MikeD:XSL+FOO+V1.20")
  
   with additional strings for specific files. (e.g. bar.xsl => bar)

   So the stylesheet file is identified with a URN like:
    
     "urn:publicid:MikeD:XSL+FOO+V1.20:bar"

   Then, if the processing tools need something like a formal PUBLIC
   identifier (FPI) to actually find the file on your machine, the URN
   is converted into an FPI by "unwrapping" the URN according to the
   OASIS XMl Catalog spec [3], as defined [1], and, in turn, looked up
   in the xcatalog (or RDDL Directory [4].)

Got that?
 
It may be a while before we can implement this stuff, but I'll work to
make sure we're up-to-speed when the time comes. 

Cheers,
Mark


[1] A URN is a globally unique name for a resource; it consists of the
    prefix "urn:", followed by a Namespace Identifier (NID) and a
    Namespace Specific String (NSS). 

[2] http://www.ietf.org/internet-drafts/draft-walsh-urn-publicid-01.txt
[3] http://www.oasis-open.org/committees/entity/spec.html#s.semantics
[4] http://www.rddl.org/
_____________________________________
Mark Johnson
Duke Physics        <mark@duke.edu>
Debian SGML         <mrj@debian.org>
Home Page:          <http://dulug.duke.edu/~mark/>
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