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Re: Non-monotonic

From: Thomas B. Passin <tpassin@comcast.net>
Date: Thu, 13 Nov 2003 19:34:22 -0500
Message-ID: <3FB4230E.7050507@comcast.net>
Cc: www-rdf-interest@w3.org

Adrian Walker wrote:
> 
> I often see statements of this kind from the RDF and semantic web folks.
> 
> In the real world, if I tell you that  
> 
>            can_fly(X) if bird(X) & not penguin(X)
>            
>            bird(Fred).
> 
> you will presumably conclude that Fred can fly.  If I later add penguin(Fred), 
> you will no longer conclude that Fred can fly.
> 
> This may sound naive, but can you argue for me please why the above should be 
> ruled out on the Semantic Web ?  Seems like you are throwing out the bird with 
> the bathwater (:-)
> 

Thinking in terms of possible interpretations, bird(Fred) would be true 
in a world in which Fred is a non-penguin bird and can fly.  It would 
also be true in a world in which Fred is a penguin and cannot fly. 
Adding a statement penguin(Fred) would serve to eliminate the first 
interpretation.  So, the manner of applying interpretations to RDF 
statements, as prescribed by the current RDF drafts, remove the possible 
problem.  Your proposed conclusion was but one possible interpretation.

Cheers,

Tom P
Received on Thursday, 13 November 2003 19:32:43 GMT

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