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Re: summary of reification?

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Wed, 6 Feb 2002 17:25:21 -0600
Message-Id: <p05101448b8876b29d4aa@[65.212.118.208]>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org
>At 12:25 PM 2/6/02 -0600, Pat Hayes wrote:
>>>I see two ways of how the semantics of reification could be attacked:
>>>
>>>1. Explain the semantics using bNode + 4-triple constructs. Applications
>>>are free to use a compact representation. If statements are used as
>>>first-class objects, they can be treated just as some kind of bNodes.
>>>The API-level identity of such bNodes is functionally determined by
>>>their (s,p,o)-description. Alternatively, the applications can generate
>>>exactly one such bNode for each (s,p,o) etc. Same trick could be applied
>>>for  dealing with functionally determined bNodes in the model theory.
>>
>>No trick is needed. The ordinary MT already would treat the 
>>4-triples in this way already; reification is semantically 
>>transparent, on this view. Which is another way of saying that we 
>>are trashing it. After all, there's no way to stop anyone writing 
>>those 4-triples if they want to, right? Trashing it doesn't make it 
>>illegal, it just says that we aren't saying anything particular 
>>about what it means: its not a language feature, its just a way you 
>>might want to write some RDF. Go ahead if y'all feel like it.
>
>I want to pick up on two points here:
>
>(1) there is provision (in RDFM&S) for a reified statement to be 
>identified (e.g. by rdf:ID='xxx' on the corresponding property 
>element), so simply saying reified statements are treated as bNodes 
>seems to miss something.

Ah, that is exactly what I wanted to focus on. WHAT DOES THAT MEAN ?? 
To 'identify' a reified statement, that is. Is the identifying ID a 
URI? If so, then why doesnt the 4-triple use that URI instead of a 
bnode? If not, what can 'identify' possibly mean in RDF?

>(2) accepting almost all of the above that the reification 
>properties are mostly like any other RDF properties, we need to 
>express a view on this entailment:
>
>     <ex:subj> <ex:prop> <ex:obj> .
>entails
>     _:r <rdf:type> <rdf:Statement> .
>     _:r <rdf:subject> <ex:subj> .
>     _:r <rdf:predicate> <ex:prop> .
>     _:r <rdf:object> <ex:obj> .
>?
>
>What you say above suggests no such entailment.

Right.

Pat

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Received on Wednesday, 6 February 2002 18:24:43 EST

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