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Re: Three solution designs to the first three Graphs use cases

From: Ivan Herman <ivan@w3.org>
Date: Fri, 27 Jan 2012 11:35:19 +0100
Cc: Sandro Hawke <sandro@w3.org>, public-rdf-wg@w3.org
Message-Id: <3E8E1C48-BD15-48D6-81E9-5C00C1B554C5@w3.org>
To: Andy Seaborne <andy.seaborne@epimorphics.com>

On Jan 27, 2012, at 10:33 , Andy Seaborne wrote:

> 
> 
> On 27/01/12 03:45, Sandro Hawke wrote:
>> On Thu, 2012-01-05 at 11:09 +0000, Andy Seaborne wrote:
>>> On 04/01/12 19:23, David Wood wrote:
>>>> Thanks, Sandro.  That's very helpful.
>>>> 
>>>> It might be useful to consider augmenting TriG syntax to support your third solution (explicitly naming relations). I'd be quite happy with that.
>>> 
>>> What would the data model be?
>> 
>> I think: an RDF graph which can have other RDF graphs as values of its
>> triples.  All these graphs would be subgraphs of some greater graph, so
>> they can share b-nodes.
>> 
>> (This is what cwm has had implemented since 2001, I think.)
> 
> I thought this WG wasn't going there (graph literals).
> 
> Personally, I see graph literals as the clean answer but it is RDF 2 (+).  RDF 1.1 is, to me, incremental improvements within the current abstract data model.  Datatyped literals  (e.g. "<s> <p> <o>"^^rdf:graphNTriples) are unwieldy and might block doing graph literals properly in RDF 2+.
> 

I am not convinced it is such a huge jump and, if this is the only way to have a clean way forward, we may have to do this. The datatyped literals may be a way forward and, after all, the trig version of using '{' may be considered as a syntactic sugar for a datatyped literal...


Ivan




> The use of explicit triples in another graph to indicate the relationship looks interesting for RDF 1.1.
> 
> Whether this should be the default graph or another "system/manifest/??" graph isn't clear to me.  For the dump "use case" it makes some sense to keep them separate.
> 
> 
> [[
> In the N3 model, a graph literal is not a subgraph of some single graph otherwise
> 
>  :s :p { :x :y :z }
> 
> would put
>  triple :x :y :z
> 
> into the outer graph (subgraphs being subsets) and it's not quoted
> 
> ]]
> 
>> 
>>>> We could also consider standardizing the existing TriG syntax to be a syntactic shorthand for TriG REST semantics; that is, a lack of explicitly declared relation infers log:semantics.
>>> 
>>> I think we should not fix a semantics for undeclared relationships.
>>> 
>>> Otherwise, it invalidates existing TriG documents which don't exactly
>>> follow the TriG/ABC definition.
>>> 
>>> Ditto N-Quads - in a quadstore/database dump or extract you don't
>>> necessary know the semantics.
>> 
>> Agreed.   If we settle on a syntax that's compatible with TriG, I think
>> we probable need the TriG subset to have the current TriG semantics --
>> roughly none.
> 
> Cool.
> 
> 	Andy
> 
> 


----
Ivan Herman, W3C Semantic Web Activity Lead
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Received on Friday, 27 January 2012 10:33:47 GMT

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