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RE: resources and URIs

From: Graham Klyne <GK@ninebynine.org>
Date: Sun, 20 Jul 2003 10:08:56 +0100
Message-Id: <>
To: "Williams, Stuart" <skw@hp.com>, pat hayes <phayes@ihmc.us>
Cc: www-tag@w3.org


There was an earlier version of that document with some words that leant 
more towards the idea of using '#' to "indirect away" from a bare URI 
denoting a web-retrievable resource:
In view of this, it is reasonable to consider that URIs without fragment 
identifiers are most helpfully used for indicating web-retrievable 
resources (when used in RDF), and URIs with fragment identifiers are used 
for abstract ideas that don't have a direct web representation. This is not 
a hard-and-fast distinction, as the line between resources having or not 
having a web-retrievable representation is sometimes hard to draw precisely.
-- http://www.w3.org/TR/2002/WD-rdf-concepts-20020829/#xtocid103660

which was drafted in large measure in an attempt to capture some of Tim's 
thoughts on this topic.  In the face of negative review comments, and the 
fact that the whole isssue is still somewhat controversial, this was 
removed from later revisions.

To my knowledge there was never, in the RDF documents, a prohibition on 
using HTTP URIs for non-web-document resources.


At 08:38 20/07/03 +0100, Williams, Stuart wrote:

> > -----Original Message-----
> > From: pat hayes [mailto:phayes@ihmc.us]
> > Sent: 19 July 2003 19:42
> > To: Williams, Stuart
> > Cc: www-tag@w3.org
> > Subject: RE: resources and URIs
> >
> >
> > >Tim (or Pat),
> > >>  No, that would be illegal by my way of thinking.
> > >> http://chandra.harvard.edu/NGC/ngc1068 is an information resource.
> > >> You would expect
> > >>
> > >>
> > >>  <rdf:Description
> > rdf:about="http://chandra.harvard.edu/NGC#ngc1068"
> > >>  rdf:type="http://chandra.harvard.edu/AOtype/Activegalaxy7"
> > >>  </rdf:Description>
> > >>
> > >>  or, in the http://chandra.harvard.edu/NGC information ressource,,
> > >>
> > >>  <rdf:Description
> > >>  rdf:about="#ngc1068"
> > >> rdf:type="http://chandra.harvard.edu/AOtype/Activegalaxy7"
> > >>  </rdf:Description>
> > >>
> > >>  where you can see that local identifiers can be used to refer  to
> > >> abstract things, because that is what the RDF language spec says.
> > >
> > >Can you provide a reference to what the RDF language spec actually says
> > >on this topic, I'd like to read it for myself.
> >
> > The relevant citation is probably
> >
>Ok... thanks.
>What I am really looking for is the source of a probibition on using http:
>scheme URI (without fragment Ids) to denote real-world things and abstract
>concepts. Tim uses the strong word 'illegal' above. I continue to fail to
>understand why he feels so strongly that this is illegal. His appeal to
>"what the RDF language spec says." appeared to be in support of the claim of
>illegality. What the RDF spec says is that URI refs with frag ids CAN be
>used for this purpose (denoting the thing described by some fragment in an
>RDF document) BUT it does not 'outlaw' the use of URI refs without frag ids
>(and particlarly http: URI without frag ids) for the same purpose - as in
>your original RDF fragment, or the 2nd fragment above which 'illegally' uses
>an unfragmented URI to denote an RDF class.
>This is the substance of httpRange-14 [1]. I think that this is tangled up
>in the distinction this thread has been discussing of an information
>resource (ie. a source of representations) and the thing the representation
>is some sense about (ie. the weather in Oaxaca or a 'galaxy far far away').
>BTW had you consider the effects of placing a super-massive black hole
>'on-the-web' or at least in close proximity to it :-)
>[1] http://www.w3.org/2001/tag/ilist#httpRange-14
> > >>I was under there impression that RDF gave URI References (2396
> > >>terminology) an entirely opaque treatment.
> >
> > The semantics treats them completely opaquely: however, existing
> > RDF/DAML/OWL *practice* seems to often follow the convention outlined
> > by Tim, where a URIref of the form ex:place#thing  denotes an entity
> > described by some RDF which can be found at the address ex:place.
>A common practice or convention, yes, but what makes it so essential as to
>regard other practices/conventions as illegal?
> > Pat

Graham Klyne
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Sunday, 20 July 2003 05:34:03 UTC

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