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Re: Islands (ACTION-148)

From: Ivan Herman <ivan@w3.org>
Date: Tue, 28 Feb 2012 17:41:40 +0100
Cc: Pat Hayes <phayes@ihmc.us>, RDF-WG <public-rdf-wg@w3.org>
Message-Id: <859D4321-F82C-47E6-961A-0FB9A194F538@w3.org>
To: Andy Seaborne <andy.seaborne@epimorphics.com>

On Feb 28, 2012, at 17:19 , Andy Seaborne wrote:

> 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.

But this also means that [2] does not work for that case, right? The 'right' way, according to [2], would be to add the func. property triple into both :g1 and :g2.

Ivan

[2] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal


> 
> 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
>> 
>> 
>> 
>> 
>> 
> 


----
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 Tuesday, 28 February 2012 16:41:58 UTC

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