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Re: Contradicting definitions of “property”

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 13 Aug 2012 14:42:32 -0500
Cc: Richard Cyganiak <richard@cyganiak.de>, RDF Working Group WG <public-rdf-wg@w3.org>, Simon Reinhardt <simon.reinhardt@koeln.de>
Message-Id: <86319BAF-88A1-4E67-A98A-295571DCD64B@ihmc.us>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>

On Aug 13, 2012, at 12:29 PM, Antoine Zimmermann wrote:

> 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. Good catch, Antoine.

Pat

> 
> 
> 
> [1] 1.2 Resources and Statements. http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#resources-and-statements
> 
> AZ
> 
>> 
>> 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
> France
> Tél:+33(0)4 77 42 66 03
> Fax:+33(0)4 77 42 66 66
> http://zimmer.aprilfoolsreview.com/
> 
> 

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Received on Monday, 13 August 2012 19:43:05 UTC

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