URNs in SYSTEM declarations

Jerome McDonough jmcdonou at library.berkeley.edu
Wed Oct 20 18:09:19 BST 1999

At 11:33 AM 10/20/99 -0400, Simon St.Laurent wrote:
>URNs are an acceptable part of the URI spec, but XML processors may have no
>way to resolve them to actual resources.  What should a validating parser
>do when confronted by:
><!DOCTYPE myDoc SYSTEM "urn:itsSoObvious">

Well, if I can restate your example to the more appropriate URN syntax of:

        <!DOCTYPE myDoc SYSTEM "urn:itsSo:Obvious">

then it should go to DNS and ask for a NAPTR record describing both the
and communication protocol for a resolution service that can resolve URNs
the "itsSo" namespace.  Then, if it supports the appropriate protocol (THTTP,
it contacts the resolver for the itsSo namespace to ask where the resource
identified by the NSS "Obvious" hangs out.  Having obtained a URL for 
urn:itsSo:Obvious from the resolver, it goes and gets the actual DTD.

Not a huge problem to implement, as long as we don't see too huge an explosion
of protocols
for contacting resolution services.  At the moment, however, THTTP and the
system are about the only resolution protocols I've seen in use.

Jerome McDonough -- jmcdonou at library.Berkeley.EDU  |  (......)
Library Systems Office, 386 Doe, U.C. Berkeley     |  \ *  * /
Berkeley, CA 94720-6000    (510) 642-5168          |  \  <>  /
"Well, it looks easy enough...."                   |   \ -- /  SGNORMPF!!!
         -- From the Famous Last Words file        |    ||||

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