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   RE: Namespaces and URNs

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  • From: Peter Murray-Rust <peter@ursus.demon.co.uk>
  • To: xml-dev@ic.ac.uk
  • Date: Wed, 05 Aug 1998 07:44:23

At 19:25 04/08/98 -0700, Charles Frankston wrote:
>Note that the examples in the namespace paper are intended to be just that
>-- hypothetical examples.  That doesn't mean that the URNs used in the
>examples have actually been registered -- they certainly have not.  However,

Thanks. Understood.

>Again, the examples are meant to be examples, and need not be consistent
>among themselves.  As John Cowan pointed out URNs, if and when they are
>widely supported, are clearly the best solution for the persistent unique
>names of XML namespaces.  Unfortunately, URNs don't really exist yet, and in
>interim URLs or other URIs can be used.  

I had assumed that the widespread use of urn: in XML-related drafts meant
that it was  a usable approach. I have kept hearing that URNs aren't quite
ready - sounds like we are still some way away. 
>I think you're confusing URNs with URI schemas.  All URNs use one schema:
>"URN".  This list you show above would indicate that you're interested in
>defining standard URNs for some popular namespaces.  While this isn't a bad
>idea, I think it will ultimately be hopeless to take on the task of tracking
>all interesting namespaces.  The namespace spec must allow for the use of

I wasn't planning to track all of them. I was suggesting that *during the
prototyping of XML-names tools* we were publicly consistent. Thus is
someone writes a namespace tool to deal with HTML4.0 there needs to be a
way for them to communicate exactly what version of HTML is meant. And we
all have to use the same string. Because that string is the only point of
having namespaces which extend beyond the document.

So if we are serious about making namespaces work we need to start using
the same strings to refer to the same namespace. I agree that that means
that DTD owners/maintainers need to be involved. Since most of the common
DTDs are within the remit of the W3C, they should be thinking of how to
identify them in namespaces. If they want to use FPIs, fine. But they
should make it clear which the FPIs *are* and use them consistently. If
they want to use URLs instead - fine. But they shouldn't encourage the use
of both simultaneously.


>> 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).
>> 	P.
>Well, you could try to be the first on your block to register a URN, if you
>could find who to register it with.

Doesn't sound very hopeful. My best strategy appears to by to put a large
notice on the CML web-site saying:

"The namespace URL (or should that be URI?) for referring to CML1.0 should
be: 'http://www.xml-cml.org/xmlns/cml10'. This is the only appropriate
string to use as an xmlns attribute value to identify CML1.0. Anyone
writing software to process CML documents should use this string to
identify whether the author intends to map the namespace onto CML1.0. No
other string should be used to identify  CML1.0 in an XML document, even if
CML resources are mounted on a different server. [By the way, the URL
doesn't actually point to an existing resource ... ]"

If you think this is a good idea, my suggestion is now that the 'DTD
owners' of the other namespaces did something similar. If we don't start
getting formal about namespace names at this stage people won't take the
process very seriously.


Peter Murray-Rust, Director Virtual School of Molecular Sciences, domestic
net connection
VSMS http://www.nottingham.ac.uk/vsms, Virtual Hyperglossary

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