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Re: Contradicting definitions of “property”

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Mon, 13 Aug 2012 19:29:51 +0200
Message-ID: <5029398F.7050309@emse.fr>
To: Richard Cyganiak <richard@cyganiak.de>
CC: RDF Working Group WG <public-rdf-wg@w3.org>, Simon Reinhardt <simon.reinhardt@koeln.de>
I know this is a very old email but I'm catching up now with some of the
WG's email I left unread. There is an inaccuracy in what you say Richard.

Le 26/04/2012 02:00, Richard Cyganiak a écrit :
> All,
> Simon Reinhardt spotted [1] a nice little contradiction between the
> 2004 versions of RDF Concepts and RDF Semantics.
> RDF Concepts states, in a normative section [2]:
> [[ The predicate is also known as the property of the triple. ]]
> Where “predicate” is defined as a URIref, one of the three components
> of a triple. RDF Semantics, on the other hand, defines [3]:
> [[ A simple interpretation I of a vocabulary V is defined by … a set
> IP, called the set of properties of I. ]]
> And the rest of the mechanics make it clear that URIrefs can denote a
> member of IP. In other words, RDF Concepts says that the predicate
> IRI *is* the property, while RDF Semantics says that it *denotes* the
> property.
> The analogy with classes shows IMO that RDF Concepts is wrong and RDF
> Semantics is right. The IRI<http://xmlns.com/foaf/0.1/Person>  *is*
> not a class, but it *denotes* a class.
> I therefore deleted the normative definition quoted above from the
> RDF Concepts ED. If you disagree with this change or see further need
> to discuss this, then please respond.
> Note that the new Introduction section in the RDF Concepts ED
> contains an *informative* sentence that introduces the term
> “property” [4], and it is in line with RDF Semantics:
> [[ The predicate itself is an IRI and denotes a binary relation, also
> known as a property. ]]

This is not what the RDF semantics says. A predicate denotes a resource 
that must be in IP, the set of properties in the interpretation. 
Resources in IP are associated with a binary relation via the extension 
function IEXT.
This is an important distinction since this is what allows RDF to talk 
about properties, classes, etc as instances.

If predicates were denoting binary relations, the following would be 
RDFS-inconsistent, when it is, in fact, RDFS-consistent:

:p  rdf:type  xsd:string .
:s  :p  :o .

This is a proposal to replace the wording in section 1.2 [1]:

"The predicate itself is an IRI and denotes a property, that is, a 
resource that defines a binary relation."

[1] 1.2 Resources and Statements. 


> Best, Richard
> [1]
> http://lists.w3.org/Archives/Public/public-rdf-comments/2012Mar/0008.html
[2] http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-triples
> [3] http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#gddenot [4]
> http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#dfn-property
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
Received on Monday, 13 August 2012 17:30:17 UTC

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