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Re: subproperty question

From: Baoshi Yan <baoshi@ISI.EDU>
Date: Thu, 25 Jan 2001 18:53:08 -0800 (PST)
To: baoshi@pollux.usc.edu
cc: www-rdf-interest@w3.org
Message-ID: <Pine.GSO.4.05.10101251852280.25353-100000@sailboat.isi.edu>


On Thu, 25 Jan 2001, Ian Horrocks wrote:

> On January 25, Arjohn Kampman writes:
> > > Stefan,
> > > 
> > > In general one wouldn't expect a sub-property of a transitive property
> > > to be transitive itself, e.g., parent as a sub-property of ancestor.
> > > 
> > > Ian
> > 
> > Related to this: I think you can state that, for a property to be transitive,
> > all of its superproperties have to be transitive too.
> > 
> > >From the RDF/S spec: "If some property P2 is a subPropertyOf another more
> > general property P1, and if a resource A has a P2 property with a value B,
> > this implies that the resource A also has a P1 property with value B."
> > 
> > Now consider P2 to be a transitive property and you have the following
> > situation:
> > 
> > 	X  --P2-->  Y  --P2-->  Z
> > 
> > In that case, X would also be related to Z through P2 and thus, as P1 is a
> > superproperty of P2, also through P1. Therefore P1 also has to transitive.
> > 
> > Please correct me if I'm wrong,
> 
> You are wrong I'm afraid. Here is a counter example:
> 
> P1 = {(x,y),(y,z),(x,z),(w,x)}
> P2 = {(x,y),(y,z),(x,z)}
> P3 = {(x,y),(y,z)}
> 
> As you can see, P3 is a subPropertyOf P2 is a subPropertyOf P1. Only
> P2 is transitive.
> 
> Regards, Ian
> 
> 
Received on Thursday, 25 January 2001 21:53:12 GMT

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