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RE: resources and URIs

From: Williams, Stuart <skw@hp.com>
Date: Sun, 20 Jul 2003 08:38:07 +0100
Message-ID: <5E13A1874524D411A876006008CD059F04A07662@0-mail-1.hpl.hp.com>
To: pat hayes <phayes@ihmc.us>
Cc: www-tag@w3.org



> -----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 
>
http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-concepts-20030117/#section-fragI
D

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

Thanks,

Stuart
Received on Sunday, 20 July 2003 03:38:31 UTC

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