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Re: ISSUE-30: How does SPARQL's notion of RDF dataset relate our notion of multiple graphs?

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 18 Apr 2011 23:45:15 -0500
Cc: "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Message-Id: <46AB8AFA-75DE-4E1D-B4EA-C5061E8F2692@ihmc.us>
To: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>

On Apr 18, 2011, at 1:52 PM, Pierre-Antoine Champin wrote:

> <snip/>
> 
> On 04/18/2011 07:58 PM, Pat Hayes wrote:
>> 
>> On Apr 18, 2011, at 9:47 AM, Pierre-Antoine Champin wrote:
>>> Well, HTTP explicitly states that a URI identifies a resource [1], and
>>> then gives semantics to the status codes one obtains when sending HTTP
>>> requests to the given URI.
>> 
>> But it is (notoriously) unclear what exactly that word 'identifies'
>> means, and several prominent Web gurus are on record with the view that
>> whatever it means, it most certainly is not synonymous with 'refers to'
>> or 'denotes' as used by semantic specifications. So it is still up to us
>> to declare what specifies the 'URI is the name of graph' relationship,
>> and how it relates to http.
> 
> I guess I need to dig a little deeper on http-range-14, then...
> 
>>> I like to think of 'identification' in HTTP as a subset of
>>> 'identification' in RDF, more precisely as the restriction of this
>>> relation to "information resources" [3].
>> 
>> The word "identification' is not used anywhere in the RDF specs, I believe. 
> 
> rephrase: I like to think that any information resource identified (as
> per HTTP) by a URI is also denoted (as per RDF) by that URI.

I agree. If we qualify this by 'identified with a 200-level response' then this is my way to phrase the http-range-14 decision. It follows that if you want the URI to *not* denote that identified thing, you have to use some other response: http-range-14 says to use 303 redirection in that case. 

>>> 
>>> So if I read
>>> 
>>> <uri1> a :G-box .
>>> 
>>> and then, by fetching <uri1>, I get a "200 Ok" and a Turtle
>>> representation (a g-text), then I would tend to consider that <uri1> the
>>> g-box "contains" the triples that I parse from the g-text.
>> 
>> That is the http-range-14 decision in a nutshell. However, what if
>> you get a 303 redirect? What if you get a 404? What if the IRI has a hash in
>> it somewhere?
> 
> Then all I can tell is that the resources is not reachable through HTTP,
> and I need other means to know more about it -- possibly more RDF about
> that resource.
> 
>> I am not meaning to imply that there are no answers to
>> these questions, only that we need to provide them.
> 
> I would be happy with the one above.

Me too, if we say it exactly right :-)

Pat

> 
>  pa
> 
> 

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Received on Tuesday, 19 April 2011 04:45:47 GMT

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