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Re: W3C specification error

From: Frank Manola <fmanola@acm.org>
Date: Mon, 29 Nov 2004 15:53:55 -0500
Message-ID: <41AB8C63.8060807@acm.org>
To: Dan Brickley <danbri@w3.org>
CC: Pat Hayes <phayes@ihmc.us>, Andrea Proli <aprol@tin.it>, www-rdf-comments@w3.org

The problem had to do with OWL compatibility.  See 
http://lists.w3.org/Archives/Public/www-webont-wg/2003Oct/0188.html
and the minutes at 
http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Nov/0063.html
(I was curious, and looked a few things up).

--Frank

Dan Brickley wrote:
> * Pat Hayes <phayes@ihmc.us> [2004-11-29 14:14-0600]
> 
>>>Thanks, I'll take a look. I remember (dimly!) the group making some 
>>>decision on
>>>this which seemed counter-intuitive. I've copied www-rdf-comments to put
>>>your note on the record, hope that's OK. I think what happened might be
>>>that the mathematics of having the more constrained form were quite
>>>tricky, so we ended up saying just 'Resource'...
>>
>>I also dimly recall this decision being made, and that at the time 
>>the reasons seemed good to me. I don't think it was because the 
>>narrower interpretation presented any particular mathematical 
>>difficulties. It may have been the observation that reification 
>>should be able to describe 'illegal' RDF, in which a non-property 
>>URIreference is used in a predicate position in a triple. At any 
>>rate, the mere possibility of such an error occurring means that one 
>>should not be able to conclude, merely from the fact of a URI being 
>>used in some RDF in this position, that it really does, in fact, 
>>denote a genuine property (which would be the effect of having the 
>>range be rdf:Property)
> 
> 
> Aha, that makes sense. I don't recall ever having realised this! Thanks :)
> 
> 
>>It might be worth remarking that to have rdfs:Resouce as a domain or 
>>range is never an error, since in RDFS domains and ranges can be 
>>conjoined. It is more like a kind of resignation: one is saying that 
>>the subject or object of the property may be anything whatsoever, 
>>unless of course further information is supplied which restricts them 
>>in some other way or for some other reason. One can see this by 
>>looking at the RDFS inference rules 
>>(http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#RDFSRules), where 
>>rdfs3 allows you to conclude in this case that the type of the object 
>>of any assertion of rdf:Property must be rdfs:Resource; but one knew 
>>that already, from rdfs4b. So this 'vacuous' range only provides some 
>>redundant information.
> 
> 
> Yep. I wish we'd given a name to the class of non-Literal resources.
> 
> (Maybe we'll make a 'handy utilities' namespace eventually...?)
> 
> cheers,
> 
> Dan
> 
> 
Received on Monday, 29 November 2004 20:48:32 UTC

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