Re: We should drop the useless urn: prefix

Dave Cridland <dave@cridland.net> Fri, 27 March 2015 12:37 UTC

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Date: Fri, 27 Mar 2015 12:37:21 +0000
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Subject: Re: We should drop the useless urn: prefix
From: Dave Cridland <dave@cridland.net>
To: Phillip Hallam-Baker <phill@hallambaker.com>
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Cc: Michael Richardson <mcr+ietf@sandelman.ca>, IETF Discussion Mailing List <ietf@ietf.org>
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On 27 March 2015 at 03:42, Phillip Hallam-Baker <phill@hallambaker.com>
wrote:

> On Thu, Mar 26, 2015 at 5:10 PM, Dave Cridland <dave@cridland.net> wrote:
> >
> >
> > On 26 March 2015 at 18:42, Michael Richardson <mcr+ietf@sandelman.ca>
> wrote:
> >>
> >>
> >> Phillip Hallam-Baker <phill@hallambaker.com> wrote:
> >>     > Since urns are not a distinct syntactic category, the
> justification
> >>     > for the urn: prefix disappears. It is not only useless, it is
> >>     > unnecessary. There is no circumstance in which a urn subscheme
> and a
> >>     > uri scheme should be allowed to have divergent meanings.
> >>
> >>     > Why make people write urn:ietf:rfc:2648 when ietf:rfc:2648 is
> >> sufficient?
> >>
> >> I must agree.
> >> This distinction has always confused me.
> >
> >
> > It's extremely useful in the XMPP world. We have both urn:xmpp (for
> protocol
> > namespaces and other abstract names) and xmpp: (for addressable entities)
> > and even xmpp:// (for client connection instructions).
> >
> > There's no confusion.
>
> Well obviously if you have an X-header and someone declares the same
> header then there is an issue. Most cases there isn't.
>
>
I have no idea what you're on about here.

All three examples given above are fully registered and described in
standards-track documents.


>
> > Of course, if we made the urn: scheme identifier optional (more or less
> what
> > PH-B appears to suggest) it'd be most interestingly confusing.
>
> I think urn: serves the same function of x-headers which is to say a
> useless syntactic distinction that leads to unnecessary confusion.
>
>
It's a moot point. Removing it now would not solve that confusion, and
would introduce more confusion.


> We should define URI schemes for DOI, UPC and ISSN and make them all top
> level.
>
>
That is an entirely different matter, and one that I struggle to care about.

That is, I don't care whether new registrations use a urn: prefix or not;
"urn:" might make clear that these are non-resolvable, I certainly dislike
the endless urn:ietf:dragons:xml-params:beware:of:the:leopard style of URN
the IETF seems to prefer to mint, but really there's more important things
in life, like whether I should put that pasty in the microwave about now.
(I think I probably should).

On the other hand, bombastically declaring that "urn:" should be stripped
everywhere without any further thought is, I think, very short-sighted;
more so in the face of obvious examples of problems.


>
> > In some cases, I've seen people use URLs to RFCs as protocol identifiers,
> > too; I recall XACML does this for LDAP attributes, which is tremendously
> > weird.
>
> Very weird since OASIS has their own urn namespace which they use in
> xacml v3 and before that was defined, SAML used the document URNs (at
> least in the specs I wrote).
>
>
Yes; these are references to LDAP attributes, and are of the form
http://www.ietf.org/... rfcXXX.txt#attributeName. I'm in no way trying to
claim this is sensible.


> Of course, if there was a prior use of a URL for that purpose it might
> have been imported. The only advantage of URNs for that application is
> to avoid unnecessary lookups when idiot software goes and slams a
> server.
>

I think including a directly addressable entity's name as a protocol
identifier is generally confusing to people, not software; at best you're
describing people as idiots, at worst you're anthropomorphising.

Of course, this rather argues against your point either way.

Dave.