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Re: Reconciliation of concerns, re islands and dataset semantics?

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Thu, 01 Mar 2012 14:31:11 +0100
Message-ID: <4F4F7A1F.8040102@emse.fr>
To: Ivan Herman <ivan@w3.org>
CC: Pat Hayes <phayes@ihmc.us>, W3C RDF WG <public-rdf-wg@w3.org>
Le 01/03/2012 13:41, Ivan Herman a écrit :
>
> On Mar 1, 2012, at 13:31 , Antoine Zimmermann wrote: [snip]
>>>
>>> If (:a owl:sameAs :b) and (:a owl:differentFrom :b) appeared in
>>> the same graph, then an OWL reasoner, using the definition of
>>> the predicates, would deduce that there is a inconsistence. I
>>> mean: the triples themselves are just fine, it is up to a
>>> reasoner to find the problem.
>>>
>>> If they are in different graphs, then the inconsistence would
>>> not occur, because we only care about the models in separate
>>> graphs, independently from one another.
>>
>> Hmm, this seems to contradict what you said above. If URIs are
>> interpreted identically in all graphs with overlapping
>> vocabularies, how can :a be interpreted as the same thing as :b and
>> at the same time as something different then :b? Either you have an
>> inconsistency, or you interpret the URIs differently in the two
>> graphs.
>>
>
> "Same thing" does not exist in RDF semantics, afaik. The only thing
> that exist are triples and other triples that can be deduced thereof.
> In my understanding, it is perfectly fine to put, into the same
> graph, the triples
>
> (:a owl:sameAs :b) (:a owl:differentFrom :b)
>
> and an interpretation 'I' can map :a and :b onto *different* elements
> in the target set (or, even, they have to do that?). It is only when
> an OWL reasoner looks at these triples that it will shout because the
> semantic condition for an OWL-interpretation are violated if that
> happens due to the special semantics of sameAs and differentFrom.
>
> If we have
>
> G1 {(:a owl:sameAs :b)} G2 {(:a owl:differentFrom :b)}
>
> The OWL reasoner will look only at I|G1 and I|G2, respectively, and
> in those constrained environment no inconsistency occurs.

You said that the interpretation could be an OWL interpretation, right?
According to the OWL semantics, :a owl:sameAs :b is satisfied iff the 
interpretation of :a is equal to the interpretation of :b (said 
differently, :a denotes the exact same thing as :b). :a 
owl:differentFrom :b is satisfied if the interpretation of :a is 
different from the interpretation :b (:a denotes a different thing than 
:b). So there cannot be an OWL interpretation that satisfies both.

Or, maybe, there is something not stated in your proposal that I don't see.

>
>
>>> [...]
>>>
>>>>
>>>> Now, if you want to do temporal reasoning, provenance, trust,
>>>> it's more complicated. But the fierceful rejection by Pat on
>>>> the mere idea of a multi-interpretation semantics has deviated
>>>> the discussion away from these issues.
>>>
>>> And I do not think this working group should deal with temporal
>>> reasoning, provenance, or trust. Just giving the basis in terms
>>> of that semantics is what should be done.
>>
>> I do not mean the WG should provide a standard for temporal
>> reasoning etc. I just mean that we have to analyse these use cases
>> in light of the various options we have for defining a semantics of
>> datasets/quads/multiple-graph structure.
>
> Ok.
>
> Ivan
>
> ---- 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
>
>
>
>
>


-- 
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/
Received on Thursday, 1 March 2012 13:31:37 GMT

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