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Re: subproperty question

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Thu, 25 Jan 2001 17:20:48 +0000 (GMT)
Message-ID: <14960.24688.233426.250572@excalibur.cs.man.ac.uk>
To: Arjohn Kampman <akam@aidministrator.nl>
Cc: stefan@db.stanford.edu, www-rdf-interest@w3.org, sintek@smi.stanford.edu
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 12:27:19 UTC

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