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Re: Another try.

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 21 Feb 2012 16:23:54 -0600
Cc: public-rdf-wg@w3.org
Message-Id: <E7037BD9-D91B-4C7B-9873-55143714D3DB@ihmc.us>
To: Andy Seaborne <andy.seaborne@epimorphics.com>

On Feb 21, 2012, at 10:00 AM, Andy Seaborne wrote:

> 
> 
> On 21/02/12 12:03, William Waites wrote:
>> On Tue, 21 Feb 2012 11:44:56 +0000, Andy Seaborne<andy.seaborne@epimorphics.com>  said:
>> 
>>     >  If I understand the quad proposal, then all existing
>>     >  vocabularies are technically undefined because they never define
>>     >  P(S,O,G), only P(S,O).
>> 
>> Back in December, I experimented with a tuple-store that understood a
>> variant of n-triples (mostly as an exercise in learning Haskell
>> properly). It had datatypes of URI, Bnode, Literal and Nil and
>> supported predicates of any arity.
>> 
>> Is it useful define such a nil value and say:
>> 
>>   For all (P, S, O), P(S,O) ->  P(S,O,nil)
> 
> Sure - I can see how it can be done if the old vocabularies are modified ... but I'm wondering if Pat's proposal forces that modification

absolutely not.

> and whether the explicit label+set of triples form does not.

They are formally equivalent, and neither of them do. 

> 
> All existing vocabularies like FOAF don't say anything about P(S,O,G) so if we just do it as an extension from pairs to triples (triples to quads), then the existing definitions that talk about pairs don't apply any ore do they?
> 
> Concretely:
> 
> :g1 { <x> foaf:age 15 }
> 
> :g2 { <x> foaf:age 25 }
> 
> In a graph foaf:age has a definition (albeit troublesome)..

Right now, this datastore contains a contradiction (well, assuming global scope of bnodes, but leave that issue aside.). If we adopt the proposal it still does, but if we instead write it as 

:g1 { <x> foaf:age 15 + )

:g2 {<x> foaf:age 25 + }

then its no longer a contradiction. Presumably, that age was recorded at different times, or under different circumstances, and the :g1/2 URIs encode these differences somehow, since they have now been treated as a genuine parameter of the foaf:age relation.

Pat

> 
>> Does this connect to SPARQL's idea of a default graph in a useful way?
> 
> Wasn't on my mind as such.
> 
>> 
>> -w
> 
> 	Andy
> 
> 

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Received on Tuesday, 21 February 2012 22:24:28 UTC

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