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

From: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>
Date: Mon, 18 Apr 2011 16:47:51 +0200
Message-ID: <4DAC4F17.3000400@liris.cnrs.fr>
To: Pat Hayes <phayes@ihmc.us>, "public-rdf-wg@w3.org >> \"public-rdf-wg@w3.org\"" <public-rdf-wg@w3.org>
[snip]

On 04/18/2011 03:40 PM, Pat Hayes wrote:
>>>>> My very sketchy feeling that if we define a good old class, say,
>>>>> G-box, we can then:
>>>>>
>>>>> - say that <g> rdf:type G-box which is the identification of a
>>>>> g-box
>>>>
>>>> This by itself would not attach the name to a particular g-box,
>>>> however.
>>
>> neither does
>>
>>  <foaf.rdf#me> a foaf:Person .
>>
>> attach the name to a particular person.
> 
> Of course; but in the case of *graph* naming, we expect more than
> simply having a description; we expect the name to be usable to actually
> locate and get (a representation of) the graph. So we need a 'baptism'
> syntax or convention which does the necessary attaching to the name to
> the graph.

We are taking about a g-box here, so "something whose state is a graph",
not the graph itself.

>>> Correct. Some hand-waving may be necessary when we define g-*.
>>
>> well, if the URI of the g-box is in the http: scheme, and it is
>> dereferenceable (with a 200 OK code), then the HTTP protocol may provide
>> that hand-waving...
> 
> Not by itself. We need to actually state (it can be as simple as a
> statement in the specs) that the http GET is what indeed identifies the
> graph being named. (And of course this statement needs to be phrased
> very carefully to allow for g-boxes and so forth; are we naming the box
> or the graph that is its state at the time of naming? What is GOT
> (GETted?) by a 404 error or a 303 redirect? And so on.)

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.

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].

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.

Note that I do not suggest that *any* g-box should be accessible through
HTTP. I can think of hidden g-boxes, imaginary g-boxes...

  pa


[1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec1.html#sec1.3
[2] http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.1
[3] http://www.w3.org/TR/webarch/#id-resources
Received on Monday, 18 April 2011 14:48:15 GMT

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