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

From: Nathan <nathan@webr3.org>
Date: Fri, 15 Apr 2011 18:14:33 +0100
Message-ID: <4DA87CF9.6000400@webr3.org>
To: Ivan Herman <ivan@w3.org>
CC: Pat Hayes <phayes@ihmc.us>, RDF Working Group WG <public-rdf-wg@w3.org>
just dropping in an old link from 2001:

   http://lists.w3.org/Archives/Public/www-rdf-interest/2001Apr/0388.html


Ivan Herman wrote:
> Thanks Pat.
> 
> I do not disagree with what you say, just putting things in context. The discussion started by the question whether the concept of Named Graphs, as used in SPARQL, are the ones we should 'elevate' into the realm of the RDF Spec as THE notion that we would use, and then declare victory. During the discussion issues like yours came up, and the way I read this resolution is that it is simply a realization that the SPARQL notion is very loose insofar as it does not make claims of any kind on the URI that is associated with a graph in a dataset (which has the consequence you note). As a practical consequence, the RDF WG is not 'bound' by the SPARQL notions, in the sense that the RDF WG may define more precisely what it means by, hm, named graphs, and should (I think) also precisely describe how those notions relate to the SPARQL world. 
> 
> One line of thought at the meeting was that we may have to have some sort of a vocabulary to characterize the relationship. Something like (I just come up with the syntax as I write this, do not take it seriously) if we have a <u,G> pair, than we can also say something like
> 
> u rdf:intention rdf:Graph_Tagging .
> 
> or
> 
> u rdf:intention rdf:Graph_Reference .
> 
> or maybe some more. And the 'default' for SPARQL is tagging (I think).
> 
> All this is still open.
> 
> Cheers
> 
> Ivan
> 
> 
> 
> On Apr 14, 2011, at 19:09 , Pat Hayes wrote:
> 
>> 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
>>
>>
>>
>>
>>
>>
> 
> 
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
> 
> 
> 
> 
> 
Received on Friday, 15 April 2011 17:15:44 GMT

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