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Re: W3C specification error

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 29 Nov 2004 14:14:46 -0600
Message-Id: <p06001f17bdd12e676563@[10.100.0.4]>
To: Dan Brickley <danbri@w3.org>, Andrea Proli <aprol@tin.it>
Cc: www-rdf-comments@w3.org

>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)

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.

Pat Hayes

>Thanks again,
>
>Dan
>
>* Andrea Proli <aprol@tin.it> [2004-11-29 02:37+0100]
>>  Dear Mr. Brickley,
>>  I think I have found an error in the W3C Specification "RDF 
>>Vocabulary Description Language 1.0: RDF Schema" (10 February 2004).
>>  Since you are the co-editor of the above mentioned specification, 
>>I thought it could be useful for you to receive this notification.
>>  However, I am new to RDF, so please forgive me in the case I'm wrong.
>>
>>  In the very last paragraph of Section "5.3.3 rdf:predicate" you 
>>wrote: "The rdfs:domain of rdf:predicate is rdf:Statement and the 
>>rdfs:range
>>  is rdfs:Resource". I found it inconsistent with previous 
>>definitions, and I argue that the rdfs:range of rdf:predicate 
>>should be rdf:Property
>>  instead of rdfs:Resource.
>>
>>  Obviously, I wrote to you because I didn't find this error in the 
>>errata section. Am I wrong about it?
>>  Thank you for your attention,
>>
>>  Andrea Proli


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Received on Monday, 29 November 2004 20:14:12 UTC

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