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Re: New Proposal (6.1) for GRAPHS

From: Steve Harris <steve.harris@garlik.com>
Date: Wed, 28 Mar 2012 20:07:33 +0100
Cc: Sandro Hawke <sandro@w3.org>, public-rdf-wg <public-rdf-wg@w3.org>
Message-Id: <6D3C57F8-7172-4D46-89BB-F8C8AECDCB65@garlik.com>
To: Ivan Herman <ivan@w3.org>
On 28 Mar 2012, at 15:51, Ivan Herman wrote:
> On Mar 28, 2012, at 16:37 , Sandro Hawke wrote:
>> On Wed, 2012-03-28 at 10:29 +0200, Ivan Herman wrote:
>>> Thanks Sandro.
>>> 
>>> In general, I think this is the way to go. Few comments
>>> 
>>> 1. You say, in 
>>> 
>>> http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1#The_Labeling_Relation
>>> 
>>> that 
>>> 
>>> "A trig document expresses an rdf:hasGraph relation between the graph label object and the RDF Graph"
>>> 
>>> do we really need to describe this in term of what seems to be a bona fide RDF triple? If we do so, how do we define the range of the rdf:hasGraph property? Obviously, the range does not include literals (we do not have graph literals) but then the range should include URI references and/or bnodes. But, in fact, the range should be graphs... Aren't graphs, as abstract terms, beyond what RDF triples describe? Aren't we opening up some flood gates here?
>> 
>> Maybe not, but for me this make everything much clearer.   To say "there
>> is a relation, and you can't mention it or work with it in RDF" ... that
>> just confused me.
>> 
> 
> But that is what happens already... Do we get into the informational vs. non-informational resource issue here? A graph is a NIR, typically; but can I talk about it without a URI?
> 
> 
>>> My alternative would be to describe 'hasGraph' as NOT an RDF property. However, we can define a class, much as your rdf:Graph class (say, rdf:GraphLabel) and say that:
>>> 
>>> <u> { a b c. }
>>> 
>>> entails 
>>> 
>>> <u> rdf:type rdf:GraphLabel
>> 
>> I don't see the value in making such a class.  Since any rdf:Resource
>> can be used as a graph label (semantically, if not syntactically), I
>> don't see this providing any functionality.
> 
> See SteveH mail. I may want to know whether a specific URI is used as a graph label or not. By automatically assigning it a type, it becomes a trivial thing to do in, say, SPARQLů

Just to be clear, I would not be in favour of inferring it from its presence in the 4th/0th column. 

My example was meant to discuss the case where it's explicitly asserted.

- Steve


>>> And we would also have something like
>>> 
>>> rdf:Graph rdfs:subClassOf rdf:GraphLabel
>>> 
>>> 
>>> 2. related to the Extension part:
>>> 
>>> http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1#Extensions
>>> 
>>> Is there any reason why we could not rdf:GraphStateResouce in the current spec? By having it as a separate class it does not interfere with applications that require only the basic labeling, but, as you yourself argued for it many times, in some applications (eg, related to Linked Data) having that 'semantics' clearly defined would make sense.
>> 
>> Perhaps not.  I'm just a bit scared of the obvious time dependence.
>> I'd rather we agree on everything else this proposal covers -- with the
>> understanding that something like this can be defined -- and then, the
>> following week perhaps, see if we can agree on something like this.
> 
> That is fine with me.
> 
> Ivan
> 
> 
>> 
>>  -- Sandro
>> 
>>> Ivan
>>> 
>>> 
>>> 
>>> 
>>> On Mar 28, 2012, at 04:23 , 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)
>>>> 
>>>> 
>>> 
>>> 
>>> ----
>>> 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
>>> 
>>> 
>>> 
>>> 
>>> 
>> 
>> 
>> 
> 
> 
> ----
> 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
> 
> 
> 
> 
> 

-- 
Steve Harris, CTO
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Received on Wednesday, 28 March 2012 19:07:56 GMT

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