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Re: model theory publication draft

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Wed, 19 Sep 2001 15:58:19 -0500
Message-Id: <p05101021b7ceaf2ae619@[]>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org
>At 12:15 PM 9/19/01 -0500, Pat Hayes wrote:
>>If anyone wants to focus, I'd suggest looking at the stuff on RDF 
>>entailment. Here's a question that occurred to me, for example. 
>>Suppose we know that
>>aaa rdf:type bbb .
>>and also
>>bbb rdfs:subClassOf ccc .
>>Now, it follows that aaa is in fact a member of the class ccc; but 
>>do we want to say that this means that
>>aaa rdf:type ccc
>>must be true? If we do, that table of RDF entailment rules would 
>>need some more entries. Right now it reflects the view that being 
>>in a class doesn't necessarily mean having that class as a type, 
>>only having some subclass of it as a type.
>From above:
>1.   <I(aaa),I(bbb)> in IEXT(I(rdf:type))
>2.   <I(bbb),I(ccc)> in IEXT(I(rdfs:subClassOf))
>From 1. and 5th rule of RDFS interpretation:
>3.   I(aaa)          in ICEXT(I(bbb))
>From 2. and 6th rule of RDFS interpretation:
>4.   ICEXT(I(bbb)) subset ICEXT(I(ccc))
>Then by 3 and 4:
>5.   I(aaa)          in ICEXT(I(ccc))
>Which is the condition for
>   aaa rdf:type ccc
>If I'm right, these means no change is needed unless aaa is NOT of 
>rdf:type ccc.

Whoops, you are right again.  Sorry. This was one I thought about 
taking out, but left in.

THIS is the case I originally had in there but decided to remove. It 
is the analogous inference for domains:

aaa rdf:domain zzz .
zzz rdfs:subClassOf yyy


aaa rdf:domain yyy

and similarly for rdf:range, of course.

The real point is that in all these cases (and there may be others) 
it really is not  completely obvious what we want to count as a valid 
RDFS inference.

If all the RDFS semantic conditions were stated strictly as iffs, 
then all of these closures would have to be used, so that for example

foo rdf:type rdf:Property

would always entail

foo rdf:domain rdfs:Resource

but right now, the domain and range truth-conditions are only 'ifs', 
not 'iffs'.


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Received on Wednesday, 19 September 2001 16:58:23 UTC

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