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Re: New Proposal (6.1) for GRAPHS

From: Ivan Herman <ivan@w3.org>
Date: Wed, 28 Mar 2012 13:34:21 +0200
Cc: Sandro Hawke <sandro@w3.org>, public-rdf-wg <public-rdf-wg@w3.org>
Message-Id: <88CDB2F7-E13F-44BB-93A3-829A5CE67F64@w3.org>
To: Steve Harris <steve.harris@garlik.com>

On Mar 28, 2012, at 13:18 , Steve Harris wrote:

> This seems good to me, assuming that the TriG docs below will have their current behaviour in SPARQL systems when imported, i.e.
> 
> SELECT ?type
> WHERE {
>   ?g a ?type .
>   GRAPH ?g { <a> <b> <c> }
> }
> 
> Will return rdf:Graph.
> 

Well... either rdf:Graph or rdf:GraphLabel (in my slight modification of Sandro's proposal). I am not sure that the default SPARQL view of the world makes any assumption on the relationship between a graph and its 'name'; my feeling is that there is none. It is only a label.

Ivan

> The only reservation I have is relating to systems where (out of the box) the default graph is the Union of the named graphs - this is relatively common. If the TriG also has:
> 
> <u3> { <u2> a foaf:Person }
> 
> Then the answer to the above query would be ?type = rdf:Graph, foaf:Person - which is not what was intended.
> 
> In 4store, for example, you could force the issue by instead asking:
> 
> SELECT ?type
> WHERE {
>   GRAPH <default:> { ?g a ?type }
>   GRAPH ?g { <a> <b> <c> }
> }
> 
> but that's not standard SPARQL, uses a system specific ugly URI, and is probably semantically dubious.
> 
> - Steve
> 
> On 28 Mar 2012, at 03:23, Sandro Hawke wrote:
> 
>> I've written up design 6 (originally suggested by Andy) in more
>> detail.  I've called in 6.1 since I've change/added a few details that
>> Andy might not agree with.  Eric has started writing up how the use
>> cases are addressed by this proposal.
>> 
>> This proposal addresses all 15 of our old open issues concerning graphs.
>> (I'm sure it will have its own issues, though.)
>> 
>> The basic idea is to use trig syntax, and to support the different
>> desired relationships between labels and their graphs via class
>> information on the labels.  In particular, according to this proposal,
>> in this trig document:
>> 
>>  <u1> { <a> <b> <c> }
>> 
>> ... we only know that <u1> is some kind of label for the RDF Graph <a>
>> <b> <c>, like today.  However, in his trig document:
>> 
>>  { <u2> a rdf:Graph }
>>  <u2> { <a> <b> <c> }
>> 
>> we know that <u2> is an rdf:Graph and, what's more, we know that <u2>
>> actually is the RDF Graph { <a> <b> <c> }.  That is, in this case, we
>> know that URL "u2" is a name we can use in RDF to refer to that g-snap.
>> 
>> Details are here: http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1
>> 
>> That page includes answers to all the current GRAPHS issues, including
>> ISSUE-5, ISSUE-14, etc.
>> 
>> Eric has started going through Why Graphs and adding the examples as
>> addressed by Proposal 6.1:
>> http://www.w3.org/2011/rdf-wg/wiki/Why_Graphs_6.1
>> 
>>    -- Sandro (with Eric nearby)
>> 
>> 
> 
> -- 
> Steve Harris, CTO
> Garlik, a part of Experian 
> 1-3 Halford Road, Richmond, TW10 6AW, UK
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> 


----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
FOAF: http://www.ivan-herman.net/foaf.rdf







Received on Wednesday, 28 March 2012 11:33:19 GMT

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