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Re: Contradicting definitions of “property”

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Thu, 23 Aug 2012 12:12:11 +0200
Message-ID: <503601FB.50103@emse.fr>
To: Richard Cyganiak <richard@cyganiak.de>
CC: RDF Working Group WG <public-rdf-wg@w3.org>, Simon Reinhardt <simon.reinhardt@koeln.de>
Le 22/08/2012 23:58, Richard Cyganiak a écrit :
> On 13 Aug 2012, at 18:29, Antoine Zimmermann wrote:
>>> 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.
>
> Ah, right. I forgot about the class/property extension stuff in RDF
> Semantics.
>
>> 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 .
>
> Do I get this right? This would be inconsistent because the first
> triple says its a Unicode string, and the second triple entails that
> it is a property, and hence (if my phrasing above were indeed
> correct) a binary relation. And a Unicode string is not a binary
> relation.
>
> And in reality, as RDF Semantics defines things, the second triple
> only entails that the Unicode string *has a property extension*, and
> the property extension is a binary relation. Hence, no contradiction.
> Anything can have a property extension.
>
> Right?

Yes.

>
>> 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."
>
> As usual, given that this is informative introduction text, there is
> a balance to be found between accuracy and simplicity. So I'd like to
> toss this around a bit.

If it is informative, then I don't object, but isn't my proposal rather 
simple?


> Is it accurate to say that the resource "defines" a binary relation?
> In what sense does it do that?

I'll use your argument: I could not find better without being overly 
complicated. It's informative, you know ;)


> Wouldn't it be slightly more accurate (but perhaps less
> understandable) to say that the predicate IRI denotes "a property,
> that is, a resource that can be interpreted as a binary relation"?

The problem is that "denotes" is a synonym of "is interpreted as", formally.

>
> How about the fuzzy but perhaps simpler: "The predicate IRI denotes a
> property, that is, a resource that can be thought of as a binary
> relation."

I like this one.


> Or: "The predicate IRI denotes a property, that is, a resource that
> can be formalized as a binary relation."
>
> I note that the overall purpose of the sentence is just to introduce
> the term "property" and give readers a decent intuition of what the
> term means. From that point of view, I still quite like the current
> phrasing ("The predicate IRI denotes a binary relation, also known as
> a property.") even though I know it's technically inaccurate. May I
> claim "harmless abuse of terminology" here?

I'd prefer "The predicate IRI denotes a property, that is, a resource 
that can be thought of as a binary relation." But I won't open an ISSUE 
for that.


>
> Best, Richard
>
>
>> [1] 1.2 Resources and Statements.
>> http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#resources-and-statements
>
>>
-- 
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/
Received on Thursday, 23 August 2012 10:12:44 UTC

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