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

From: Antoine Zimmermann <antoine.zimmermann@gmail.com>
Date: Thu, 14 Apr 2011 21:36:55 +0200
Message-ID: <4DA74CD7.3030806@insa-lyon.fr>
To: Pat Hayes <phayes@ihmc.us>
CC: Ivan Herman <ivan@w3.org>, RDF Working Group WG <public-rdf-wg@w3.org>
Our decision today was about SPARQL datasets and what the URI in the
<n,G> pairs is referring to. We said it does not necessarily identify 
the graph in the sense of what the RDF semantics says (the 
interpretation of n does not need to be the graph). This is enough to 
define a notion of interpretation and model of a dataset, as explained 
in section "Interpreting datasets" of 
http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal.

Now, the use cases clearly show that we need a way to identify a graph 
(or rather a g-box) with a URI. My understanding was that this is 
independent from today's decision, and I hope it is.

So all is good so far.


Le 14/04/2011 19:09, Pat Hayes a écrit :
> Well, the use of a URI inside an RDF triple assumes that the URI is
> being used as a name, to refer to something. Using a URI which is the
> name of a named graph, for example, would refer to the graph. But in
> this decision we *explicitly* say that this is *not* how the SPARQL
> association of URIs to graphs works: that the 'associated' graph
> which is 'tagged' (if I have that right) by a URI might well not be
> the entity referred to by the URI. The example was given in which the
> URI is the name of a person, ie refers to a person, and still can be
> used to 'tag' a graph for SPARQL purposes. If such a URI is used as
> the object of an RDF triple, it will refer to the person, not to the
> SPARQL-tagged graph. As there is no way to know whether the graph
> that is SPARQL-tagged by a URI is, or is not, the referent of the
> URI, any use of that URI as a name inside an RDF triple must be
> basically unrelated to its use as a SPARQL graph tag; or at any rate,
> that is the only safe assumption to make.
>
> In a nutshell, RDF uses URIs as referring names. Apparently, SPARQL
> does not, when it comes to identifying graphs. So the uses of URIs in
> RDF triples and in SPARQL tags are dissociated from one another, and
> need have no relationship. So, no relationship can be relied upon.
> The 'naming' of graphs in SPARQL is a wholly SPARQL-local business,
> unrelated to RDF semantics and therefore to any RDF content.
>
> I assumed this was obvious at the time we were discussing this, by
> the way. But I confess I had not at that time read the Wiki proposal
> fully, and not seen the 'imports' examples.
>
> Pat
>
> On Apr 14, 2011, at 11:55 AM, Ivan Herman wrote:
>
>> Pat,
>>
>> sorry, but you will have to explain (me) what the problem is.
>>
>> Ivan
>>
>> ---- Ivan Herman web: http://www.ivan-herman.net mobile: +31 64
>> 1044 153
>>
>> On 14 Apr 2011, at 18:43, Pat Hayes<phayes@ihmc.us>  wrote:
>>
>>> I note in passing that the Proposed WG Decision dated 14 April
>>> has the consequence that the IRi associated with a graph in
>>> SPARQL cannot be used inside an RDF triple to reliably refer to
>>> the graph. This means in particular that uses such as those
>>> contemplated in
>>> http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal,
>>> which use the SPARQL name as the object in an 'imports' triple,
>>> are ruled out by this decision.
>>>
>>> Pat
>>>
>>> On Apr 13, 2011, at 4:29 AM, RDF Working Group Issue Tracker
>>> wrote:
>>>
>>>>
>>>> ISSUE-30: How does SPARQL's notion of RDF dataset relate our
>>>> notion of multiple graphs?
>>>>
>>>> http://www.w3.org/2011/rdf-wg/track/issues/30
>>>>
>>>> Raised by: On product:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> ------------------------------------------------------------ IHMC
>>> (850)434 8903 or (650)494 3973 40 South Alcaniz St.
>>> (850)202 4416   office Pensacola
>>> (850)202 4440   fax FL 32502
>>> (850)291 0667   mobile phayesAT-SIGNihmc.us
>>> http://www.ihmc.us/users/phayes
>>>
>>>
>>>
>>>
>>>
>>>
>>
>
> ------------------------------------------------------------ IHMC
> (850)434 8903 or (650)494 3973 40 South Alcaniz St.
> (850)202 4416   office Pensacola                            (850)202
> 4440   fax FL 32502                              (850)291 0667
> mobile phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
>
>
>
>
>
>
Received on Thursday, 14 April 2011 19:37:27 GMT

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