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Re: About rdfs:member and rdf:_nnn

From: Qu Yuzhong <yzqu@seu.edu.cn>
Date: Wed, 19 Feb 2003 19:32:58 +0800
Message-ID: <005801c2d80a$a7bf4d40$110f77ca@proxy.seu.edu.cn>
To: "Brian McBride" <bwm@hplb.hpl.hp.com>, "pat hayes" <phayes@ai.uwf.edu>
Cc: "rdf-comments" <www-rdf-comments@w3.org>

> At 11:25 18/02/2003 -0600, pat hayes wrote:
> [...]
> >>2. About rdf:_nnn  (section 3.2.2 of the RDF Semantics spec)
> >>
> >>Please consider adding one more example to clarify the meaning of 
> >>rdf:_nnn, such as the following:
> >>
> >>_:xxx rdf:type rdf:Seq.
> >>_:xxx rdf:_2 <ex:a> .
> >>_:xxx rdf:_2 <ex:c> .
> >>
> >><ex:a> and <ex:c> should denote the same thing? In other words, the 
> >>property rdf:_nnn should be a functional property? (I haven't found any 
> >>explanation about this issue in the spec)
> >
> >Since RDFS has no notion of equality, there is no way to express the idea 
> >of a functional property in RDFS. Whether or not a property is functional 
> >can make no difference to any RDFS entailment. In semantic extensions like 
> >OWL which can express the idea of a functional property, it would 
> >certainly be natural to impose this requirement; but then that must be 
> >part of the spec of the extended language.
> Qu,
> Does Pat's explanation of the absence of this entailment resolve your 
> issue, or would you like the WG to consider this as a formal last call comment?

Yes, RDFS has no explicit notion of equality and functional property. But we can specify rdf:_nnn to be a functional property by an extra semantic condition for rdf-interpretation (refer section 3.1). For example, add an extra semantic condition as follows:

If <x,y1> and <x,y2> are in IEXT(I(rdf:_nnn)) then y1 equals y2 in IR.

(This also reveals the powerfulness, maybe ambitious, of the semantic framework in the spec.) 

Pat's response partially resolves my issue. Hope the WG could consider this as a formal last call comment.

BTW, I haven't received any response to my another comment with the subject "Some comments on the spec of RDF Semantics". That comment is more about editorial issues.

Yuzhong Qu

> Brian
Received on Wednesday, 19 February 2003 06:35:46 UTC

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