xml-dev - Re: URNs in SYSTEM declarations

[Jerome McDonough <jmcdonou@library.berkeley.edu>]

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
location
and communication protocol for a resolution service that can resolve URNs
within
the "itsSo" namespace.  Then, if it supports the appropriate protocol (THTTP,
say),
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
Handle 
system are about the only resolution protocols I've seen in use.



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