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Re: Islands (ACTION-148)

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 28 Feb 2012 21:37:41 -0600
Cc: public-rdf-wg@w3.org
Message-Id: <9580BDB4-C397-4D50-89B1-4F4253725F9E@ihmc.us>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>

On Feb 28, 2012, at 11:50 AM, Antoine Zimmermann wrote:

> As it is good to get down to earth with use cases, I'll start with the following case:
> 
> [2] would simply consider the 2 graphs to be independent because possibly, you do not trust :g3 and it's a malevolant piece of RDF. So, there would not much entailment, even assuming OWL entailment inside each graphs.

No. Look, we agreed on this in an earlier exchange: trust is one topic, truth is another. Suppose you dont trust :g3. Still, what :g3 actually says is what it is, whether or not you trust it. Your trusting it or not does not change what it says about the world; in fact, you may mistrust it *because* of what it says about the world (eg because that is wildly inconsistent with something else you believe to be true.) Refusing to believe it does not change what it means, or what it is claiming (ie what the world would have to be like IF it were true, which of course you don't believe it to be.) And refusing to accept it does not change any entailments it has. Maybe you refuse to accept the conclusions of those entailments, of course, since you don't accept their antecedent, but that does not change the actual entailment relationship between them (which is all that the semantics cares about). One being equal to zero entails that I am the Pope. I don't believe either of these propositions, but I don't need to deny the actual entailment. 

> 
> However, if an application is using an internal ontology which happens to contain the triple :
> 
> :age a :FunctionalProperty .
> 
> that application may decide that it must be merged with any other graphs it indexes. Then the same application meets a document with the triple :
> 
> :Joe :age 10 .
> 
> It mints a URI to put it in a "named" graph (say, :g1) then it meets another graph later on:
> 
> :Joe :age 20 .
> 
> It mints a new URI (say :g2). Since the application already have its internal ontology which it decides to merge with any graph, the following dataset will be contained in that app RDF store:
> 
> :g1 { :Joe :age 10 . :age a :FunctionalProperty .}
> :g2 { :Joe :age 30 . :age a :FunctionalProperty .}
> 
> This leads to a lot of duplication of course, but it's trivial to optimise this without repetition. Then you have both assertional data and terminological data in the same "named" graph, so you can do useful inferences, which won't affect consistency globally.

Im not sure what the point of this is. Yes, you can build something that will act in this way, clearly. I don't know why you would want to, but you could. But what has any of this got to do with semantics and entailment?

Pat

> 
> 
> AZ.
> 
> Le 28/02/2012 17:51, Andy Seaborne a écrit :
>> 
>> 
>> On 28/02/12 16:41, Ivan Herman wrote:
>>> 
>>> 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.
>> 
>> Pat's example was 3 different graphs. An app can decide to use the :g3
>> ontology is useful and that it thinks :g1 and :g2 have used it
>> correctly. It can then use it with :g1 or on :g2 if it wants. Using on
>> :g1 union :g2 is not good. This is a decision the app makes before the
>> formal systems kick in.
>> 
>> Andy
>> 
>>> 
>>> Ivan
>>> 
>>> [2] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal
>> 
>> 
> 
> -- 
> Antoine Zimmermann
> ISCOD / LSTI - Institut Henri Fayol
> École Nationale Supérieure des Mines de Saint-Étienne
> 158 cours Fauriel
> 42023 Saint-Étienne Cedex 2
> France
> Tél:+33(0)4 77 42 83 36
> Fax:+33(0)4 77 42 66 66
> http://zimmer.aprilfoolsreview.com/
> 
> 

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Received on Wednesday, 29 February 2012 03:38:17 UTC

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