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Re: Part II: Response to Peter F. Patel-Schneider

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 06 Apr 2009 09:48:34 -0400 (EDT)
Message-Id: <20090406.094834.11202781.pfps@research.bell-labs.com>
To: schneid@fzi.de
Cc: public-owl-wg@w3.org
From: "Michael Schneider" <schneid@fzi.de>
Subject: Part II: Response to Peter F. Patel-Schneider [RE: review of RDF-Based Semantics]
Date: Mon, 6 Apr 2009 15:08:03 +0200

[...]

> ad (2):
> 
> First, if x and y are required to be instances of NamedIndividual, as a
> "simulation" for the notion of being named in the ontology, then I think
> this has to be the case for the other variables as well, because the
> individuals are also required to be ISNAMED in the Direct Semantics
> version of keys axioms.
> 
> However, I believe that NamedIndividual is not an adequate substitution
> for the "ISNAMED" operator in the Direct Semantics. Even for valid OWL 2
> DL ontologies it is not required in every case that a (named) individual
> IRI needs to be declared as an owl:NamedIndividual. So requiring that
> the variables are instances of owl:NamedIndividual would lead to a
> /weaker/ semantic condition compared to the Direct Semantics.
> 
> But I see an even bigger problem with the practical use of Key axioms
> under the RDF-Based Semantics, in particular when people don't care
> about OWL 2 DL-ness of their ontologies.  If we would do the change as
> you propose, then people would be required to add owl:NamedIndividual
> declarations to names in order to apply the semantic condition of
> owl:hasKey axioms. For example, if one wants to use Keys with an
> existing triple store, one would first have to add owl:NamedIndividual
> typing triples to the resources, in order to make the axiom work.
>  
> Further (and related to the previous point), this change would also have
> a side effect on the "Profiles" document. The OWL 2 RL rule for
> "owl:hasKey" would need to be changed as well, by requiring that "?x"
> and "?y" (and potentially the other variables, either) be of type
> owl:NamedIndividual. Otherwise, the OWL 2 RL rules would become unsound
> w.r.t. OWL 2 Full, because they would fire "without restriction" (even
> on bNodes, for example).
> 
> Based on these arguments, I prefer to *not* perform the change.
>    
> Best,
> Michael

This is fine by me.

peter
Received on Monday, 6 April 2009 13:46:34 GMT

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