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Re: Semantics of rdf:Statement

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Mon, 23 Jul 2007 11:00:40 +0200
Message-ID: <46A46E38.20603@uva.nl>
To: Richard Cyganiak <richard@cyganiak.de>
CC: semantic-web@w3.org, Alexander Boer <aboer@uva.nl>, Thomas Gordon <thomas.gordon@fokus.fraunhofer.de>
Dear Richard,

Thanks for your comments (and warning): I will tread carefully... I was 
trying to read between the lines of the spec, but I guess the spec has 
been left intentionally vague (cf. Bijan's reply).

Best,

	Rinke

Richard Cyganiak wrote:
> 
> Rinke,
> 
> On 20 Jul 2007, at 12:36, Rinke Hoekstra wrote:
>> I have a question regarding the rdf:Statement mechanism for 
>> reification: what is the semantics of an rdf:Statement consisting of 
>> multiple subject, predicate and object properties?
> 
> The RDF spec doesn't define any semantics at all for reification. Thus, 
> in standard RDF, the example you've given below is just a bunch of 
> meaningless triples.
> 
> People who use RDF reification assign their own private, local meaning 
> to the reification vocabulary. That's fine as long as you are in a 
> closed system. Of course you have to be very careful when exchanging 
> reified statements with other parties. (In other words: You probably 
> shouldn't.)
> 
> Regarding your example with multiple rdf:subject, rdf:predicate and 
> rdf:object statements, all I can say is: Don't.
> 
> Best,
> Richard
> 
> 
>>
>> As far as we can tell, the RDF spec. is silent on this issue, and 
>> leaves implicit whether there is a 1:1 mapping between a triple and 
>> its reification as a rdf:Statement.
>>
>> Supposing this 1:1 mapping holds, the following RDF should be 
>> incorrect, or at least problematic:
>>
>> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
>>     <rdf:Statement rdf:ID="S1">
>>       <rdf:subject 
>> rdf:resource="http://www.leibnizcenter.org/information/people/rinke-hoekstra" 
>> />
>>       <rdf:subject 
>> rdf:resource="http://www.leibnizcenter.org/information/people/alexander-boer" 
>> />
>>       <rdf:predicate 
>> rdf:resource="http://description.org/schema/Creator"/>
>>       <rdf:predicate rdf:resource="http://description.org/schema/Fish"/>
>>       <rdf:object rdf:datatype=
>>          "http://www.w3.org/2001/XMLSchema#string">Rinke Hoekstra
>>       </rdf:object>
>>       <rdf:object rdf:datatype=
>>          "http://www.w3.org/2001/XMLSchema#string">Alexander Boer
>>       </rdf:object>
>>     </rdf:Statement>
>> </rdf:RDF>
>>
>> The above example implicitly states that 
>> http://www.leibnizcenter.org/information/people/rinke-hoekstra and 
>> http://www.leibnizcenter.org/information/people/alexander-boer, and 
>> http://description.org/schema/Creator and 
>> http://description.org/schema/Fish pairwise point to the same 
>> resource. This is fine.
>>
>> However, for datatype resources this is really problematic as the 
>> above RDF states that the *strings* "Rinke Hoekstra" and "Alexander 
>> Boer" are equal. Something which is clearly not true...
>>
>> The W3C RDF Validator validates the above RDF as being correct. Is 
>> this intended?
>>
>> Thanks,
>>
>>     Rinke Hoekstra
>>
>> -- 
>> ----------------------------------------------
>> Drs. Rinke Hoekstra
>>
>> Email: hoekstra@uva.nl   Skype:  rinkehoekstra
>> Phone: +31-20-5253499    Fax:   +31-20-5253495
>> Web:   http://www.leibnizcenter.nl/users/rinke
>>
>> Leibniz Center for Law,         Faculty of Law
>> University of Amsterdam,           PO Box 1030
>> 1000 BA  Amsterdam,            The Netherlands
>> ----------------------------------------------<hoekstra.vcf>
> 

-- 
----------------------------------------------
Drs. Rinke Hoekstra

Email: hoekstra@uva.nl   Skype:  rinkehoekstra
Phone: +31-20-5253499    Fax:   +31-20-5253495
Web:   http://www.leibnizcenter.nl/users/rinke

Leibniz Center for Law,         Faculty of Law
University of Amsterdam,           PO Box 1030
1000 BA  Amsterdam,            The Netherlands
----------------------------------------------

Received on Monday, 23 July 2007 09:00:55 UTC

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