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Re: Islands (ACTION-148)

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 28 Feb 2012 16:19:02 +0000
Message-ID: <4F4CFE76.2010804@epimorphics.com>
To: Pat Hayes <phayes@ihmc.us>
CC: Ivan Herman <ivan@w3.org>, RDF-WG <public-rdf-wg@w3.org>
Pat,

The fact you can have

:g1 { :Joe :age 10 }
:g2 { :Joe :age 30 }
:g3 { :age a :FunctionalProperty }

is the point.  It's not about graph consistency until the app decides it 
wishes to apply RDF machinery to some combination of :g1 :g2 and :g3. 
How it does that is not spec'ed - it would be nice if it were, but given 
timescales, state of the art, etc, it's where the deployed semweb 
currently is.

Would you prefer it if we said that a TriG had no interpretation, that 
it was just a transport format?

	Andy

On 28/02/12 15:36, Pat Hayes wrote:
>
> On Feb 28, 2012, at 3:45 AM, Ivan Herman wrote:
>
>> Pat,
>>
>> I need explanation, 'cause I am lost, I am not ashamed to say that...
>>
>>
>> On Feb 27, 2012, at 22:42 , Pat Hayes wrote:
>> [snip]
>>>
>>>>
>>>> The use of a URI for a graph label in two different trig documents should mean the same thing but combining two datasets, like combining two graphs, will involve an application deciding that is can be done.
>>>
>>> But how will it? ANY two graphs are semantically consistent, on this account,
>>
>> If my understanding of [2] is correct, each graph must be, individually, consistent according to the RDF Semantics, ie, has to have a proper model. The models may be different for two different graphs with different labels, but I do not understand what you say...
>
> I should have said, any two graphs are consistent *with one another*. Put another way, there cannot be an inconsistency between something said on one graph and something said in a different graph. For example, suppose one graph says that :Joe :age '10'^^xsd:number and another graph says that :Joe :age '33'^xsd:number and a third graph says (in OWL) that :age is a functional property. Something wrong here, right? But no, not according to the proposed semantics. Put these three graphs into a single trig document, and this document has an interpretation, so it is consistent. So there is no inconsistency to be resolved: everything is fine, according to this semantics.
>
>>> and two graphs (with different labels) NEVER entail any graph larger than either of them (such as their merge, for example), according to the semantics in [2].
>>
>> Again, I do not understand why. If two graphs have the same label, then their merge, with the same label, is entailed, again by [2].
>
> With the same label, yes. I said, two graphs with different labels. If I put two copies of a graph into a single trig document with two different lables, one of the copies does not entail the other, even though they are the same graph.
>
> Pat
>
>>
>> Ivan
>>
>>
>>
>>> So all semantic relationships are reduced to triviality, so there can be no criteria available to check for acceptability on any semantic grounds. Remember, *every* URI might mean sometjhing completely different in another graph, so you can't say things like one graph says that x:joe is age 10 and the other says he is age 12: that URI might refer to Joe in one graph and Susan in the other, and the URI for the age property might mean age in one graph and being-a-handle-of in the other. Graphs become black holes of meaning, without any way for anything inside to influence or connect with anything outside.
>>>
>>>>
>>>> Islands aren't named or formally recognized - and one apps view of "usable together" may not be the same as another apps.
>>>
>>> Oh what a tangled Web we weave.... (Sorry, couldnt resist :-)
>>>
>>> Pat
>>>
>>>>
>>>> 	Andy
>>>>
>>>> [1] http://www.bbc.co.uk/doctorwho/dw
>>>> [2] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal
>>>>
>>>>
>>>
>>> ------------------------------------------------------------
>>> 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
>> FOAF: http://www.ivan-herman.net/foaf.rdf
>>
>>
>>
>>
>>
>
> ------------------------------------------------------------
> 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
>
>
>
>
>
Received on Tuesday, 28 February 2012 16:19:41 UTC

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