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Re: Multiple (conflicting) rdfs:range properties

From: Alexander Pohoyda <alexander.pohoyda@gmx.net>
Date: Thu, 20 Jul 2006 19:24:24 +0200 (CEST)
Message-Id: <200607201724.k6KHOOPE000384@oak.pohoyda.family>
To: Frank Manola <fmanola@acm.org>
CC: www-rdf-interest@w3.org

Frank,

Thank you very much!  The section 4.3 ("A Note on rdfs:Literal") of
RDF Semantics document answers my question.

I suspected that "ex:a rdf:type rdfs:Literal" is a logical
contradiction just like a "this statement is false" statement.

I had a feeling that a URI reference cannot be declared a literal, but
I see that this is not the case and RDF Semantics explicitely allows
this.



> Alexander--
> 
> I'm not exactly sure what distinction you have in mind between
> "formal" and "logical" contradiction, but I don't think this example
> is a contradiction in either case.
> 
> For there to be a problem with a resource being both an instance of
> both the rdfs:Literal and my:Class1 classes, there would have to be
> an *RDFS* condition saying that rdfs:Literal was disjoint from other
> RDFS classes.  But there is no such condition in RDFS.
> 
> Note that a "logical" contradiction requires that there be
> conflicting statements *in the logic* (statements to which the logic
> applies).  What I think you have in mind is that this doesn't make
> sense in your intended interpretation (but RDFS doesn't provide a
> way to state all the constraints that apply to that interpretation).
> 
> You might want to have a look at Section 4.3 ("A Note on
> rdfs:Literal") of RDF Semantics
> <http://www.w3.org/TR/rdf-mt/#literalnote>.
> 
> --Frank
> 
> PS: It is very difficult to write contradictory statements in RDFS,
> due to its limited expressibility.  However, the end of Section 4.1
> of RDF Semantics describes one case, involving XML literals, where
> it is possible.  Datatyped interpretations in general (see Section
> 5) introduce another area in which contradictions are possible, but
> this involves considering the extra semantic conditions introduced
> by the datatype(s)involved.
> 
> 
> Alexander Pohoyda wrote:
> > Hello,
> > 
> > Definition from RDF Schema:
> > 
> >     3.1 rdfs:range
> > 
> >         P rdfs:range C
> > 
> >     Where P has more than one rdfs:range property, then the resources
> >     denoted by the objects of triples with predicate P are instances
> >     of all the classes stated by the rdfs:range properties.
> > 
> > 
> > Now, consider an example:
> > 
> >     my:property1 rdfs:range rdfs:Literal, my:Class1.
> > 
> > 
> > This effectively means that any object I use with this predicate is
> > an instance of both rdfs:Literal and my:Class1 classes:
> > 
> >     example:thing1 my:property1 example:thing2.
> > 
> > 
> > Formally this is not a contradiction.  But isn't it a contradiction
> > logically?
> > 
> > I appreciate any answer.  Thank you!


-- 
Alexander Pohoyda <alexander.pohoyda@gmx.net>
PGP Key fingerprint: 7F C9 CC 5A 75 CD 89 72  15 54 5F 62 20 23 C6 44
Received on Thursday, 20 July 2006 17:27:01 GMT

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