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   Re: Namespaces and URNs

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  • From: John Cowan <cowan@locke.ccil.org>
  • To: XML Dev <xml-dev@ic.ac.uk>
  • Date: Tue, 04 Aug 1998 16:31:14 -0400

Peter Murray-Rust wrote:

> (A) The NS draft gives an example as
>         xmlns='urn:loc.govs:books'
> but a private correspondent tells me than URNs should be of the form
> urn:scheme:something - so unless loc.gov is a scheme there appear to be
> differences of opinion.

Your correspondent is correct per RFC 2141 (http://www.isi.edu/in-notes/rfc2141.txt)
but no particular schemes (there called NIDs, Namespace Identifiers)
are defined there or elsewhere in the RFCs.  So "loc.gov" could
be a scheme name, although if it were I at least would expect that
the "something" would be a Library of Congress call number, not
something vague like "books".

RFC 1737 says vaguely that ISBNs, ISO public identifiers (what are
those, please?) and UPC product codes "seem to satisfy the functional
requirements" of URNs.

The only publicly available Internet-Draft that actually proposes
an URN scheme proposes "ietf", for RFCs, minutes of IETF working
groups, and so on.

> Are these equivalent? If so, there must be a central registry of synonyms
> somewhere. And, if so, it places a great burden on implementers who must
> search the WWW for all possible equivalences. I would *much* prefer that
> the whole world used exactly the same string for the namespace for HTML4.0.

Efforts are underway to help with URN resolution, but nothing is
set up yet.

> Having developed 2 DTDs (CML and VHG) I need to know how to prepare URNs
> for them. It seems clear that anyone wishing to create a DTD which can be
> used for Namespaces has to buy/borrow a domain name. (I suppose they could
> buy an FPI instead, but since I already have domain names I'd prefer to
> stick with those).

For the moment, the best hope is to use URLs and try to make sure
they are as persistent as possible, either using PURLs or some
informal scheme.  After all, Java package names are in effect URNs
for packages, and the existing scheme works well enough: most people
have at least an email address they can use.

John Cowan	http://www.ccil.org/~cowan		cowan@ccil.org
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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