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Re: RDF Issue rdfs-clarify-subClass-and-instance

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 27 Aug 2002 18:02:41 -0700
Message-Id: <p05111b01b9916c38d439@[65.212.118.251]>
To: "Seth Russell" <seth@robustai.net>
Cc: "graham wideman" <graham@wideman-one.com>, "Frank Manola" <fmanola@mitre.org>, "Brian McBride" <bwm@hplb.hpl.hp.com>, <www-rdf-comments@w3.org>

>From: "pat hayes" <phayes@ai.uwf.edu>
>
>>  A is a subclass of B just when every member of A is a member of B.
>>  That's all there is to it: there is no inheritance or 'transferring'
>>  between the classes. This isn't OOP.
>
>Can't I write:
>
><B> my:haveQuality <E>.
><A> rdfs:subclassOf <B>.
><x> rdf:type <A>.
>
>and mean that:
>
><x> my:haveQuality <E>.
>
>??
>
>Now I do understand that the RDF MT does not sanction that entailment.

Indeed, it does not. It would be a mistake, in general. For example, 
the class of classes is (arguably) infinite; but it would be wrong to 
conclude that every class in it was infinite. This hasn't got 
anything to do with the subClass part, by the way: it doesn't follow 
from

<B> my:haveQuality <E> .
<x> rdf:type <B> .

that

<x> my:haveQuality <E>

either. Properties of classes are not, in general, inherited by their members.

You might want to define a class of special properties which are 
inherited from classes to members, and then you could state your 
inference with one additional premis and it would be safer. If the 
relevant class is my:inheritingPRoperties, for example, then you 
could say

<E> rdf:type my:inheritingProperty .

Or, just add

my:haveQuality rdfs:domain my:inheritingProperty .

to your KB. I would advise *not* asserting that rdf:type was a 
my:inhertingProperty :-)

>But
>does it prevent me from meaning that entailment when I write the triple {B
>my:haveQuality D} ?   Here the 'my' is a prefix bound to *my own namespace*.

Of course, you can understand anything to mean anything, so yes, 
*you* can impose that inference. But its not RDFS-valid, so its not 
an RDFS inference. That is, you can't expect anyone else (who doesnt 
know your private rules and is following the RDFS spec) to be able to 
follow your reasoning here or to be able to verify it. Also, you had 
better be careful or your knowledge-base might have some hidden 
contradictions lurking in it.

Pat
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Received on Tuesday, 27 August 2002 21:01:47 GMT

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