W3C home > Mailing lists > Public > www-rdf-interest@w3.org > September 2001

Re: Bitzi File Metadata RDF Dump

From: Graham Klyne <GK@NineByNine.org>
Date: Thu, 27 Sep 2001 15:39:37 +0100
Message-Id: <>
To: fmanola@mitre.org
Cc: www-rdf-interest@w3.org
At 10:07 AM 9/27/01 -0400, Frank Manola wrote:
>Graham Klyne wrote:
> >
> > At 07:37 PM 9/26/01 +0300, Patrick.Stickler@nokia.com wrote:
> > >While URLs and URNs no longer are considered to represent disjunct
> > >partitions of URI space, they still (to my understanding) are considered
> > >to be valid and necessary concepts distinguishing between resources
> > >which are expected to have some "physical" online realization and
> > >those which are trully abstract.
> > >
> > >For those who haven't seen it yet, cf
> > >http://www.w3.org/TR/2001/NOTE-uri-clarification-20010921/.
> >
> > Er, the disjointness of URLs and URNs is one of the few definite
> > distinctions that is asserted by that document:
>If you really mean this disjointness to be considered as definite as all
>that, you're going to have to say it in a more explicit way than either
>of the two quotations below, particularly in view of the following, also
>from Section 1.2:  "the view became that an individual scheme does not
>need to be cast into one of a discrete set of URI types such as "URL",
>"URN"..." , and the fact that "URI space was thought to be partitioned
>into two classes:  URL and URN" is described as being part of the
>"Classical View", not the "Contemporary View". Is the idea that:
>a.  These distinctions were made in the past, and continue to be very
>important, or
>b.  These distinctions were made in the past, but are deprecated now, or
>c.  something else?

My answer is (c):  something else.  URN no longer being regarded as a "URI 
type", but a specific URI scheme called "urn:".

1.2 Contemporary View

Over time, the importance of this additional level of hierarchy seemed to 
lessen; the view became that an individual scheme does not need to be cast 
into one of a discrete set of URI types such as "URL", "URN", "URC", etc. 
Web-identifer schemes are in general URI schemes; a given URI scheme may 
define subspaces. Thus "http:" is a URI scheme. "urn:" is also a URI 
scheme; it defines subspaces, called "namespaces". For example, the set 
of  URNs of the form "urn:isbn:n-nn-nnnnnn-n" is a URN namespace. ("isbn" 
is an URN namespace identifier. It is not a "URN scheme" nor a "URI scheme").
-- http://www.w3.org/TR/2001/NOTE-uri-clarification-20010921/

Maybe this point could be made more clearly.


Graham Klyne
Received on Thursday, 27 September 2001 10:40:28 UTC

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