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Re: Some advice on inferring negated properties

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Thu, 16 Aug 2007 19:48:50 +0100
Message-Id: <5D8907A4-2A74-4FFE-BC84-9C75F350BD54@cs.man.ac.uk>
Cc: Owl Dev <public-owl-dev@w3.org>
To: "Swanson, Tim" <tim.swanson@semanticarts.com>

On Aug 16, 2007, at 7:16 PM, Swanson, Tim wrote:

> Am I missing something here?

I think so.

> It seems to me that, in order to say that the property assertion (a  
> P b) does not hold, you can say this:
>
> <owl:Thing rdf:about="#a">
>   <rdf:type>
>     <owl:Class>
>       <owl:complementOf>
>         <owl:Restriction>
>           <owl:onProperty rdf:resource="#P"/>
>           <owl:hasValue rdf:resource="#b"/>
>         </owl:Restriction>
>       </owl:complementOf>
>     </owl:Class>
>   </rdf:type>
> </owl:Thing>

That's one way. (OWL 1.1 lets you do others.) I mentioned it in my  
email:
	"""ClassAssertion(a, ObjectComplementOf (ObjectHasValue(P, b)))""""

> Although this seems verbose (especially in RDF/XML), it's really  
> just saying that 'a' is not a member of the set of things that have  
> the property 'P' with the filler 'b'.
>
> An approach like the one Bijan suggested:
>
>>> 	ClassAssertion(a, ObjectMaxCardinality(0, P, owl:Thing))
>>> 	ClassAssertion(b, owl:Thing)
>
> Is making the more general assertion that a cannot have /any/  
> instances of property P.

Yep. But please recognize that I used that as an example of how to  
*entail* a negated property assertion. I wanted to have an example  
where you weren't just paraphrasing the assertion you were looking for.

> The approach I've outlined above seems to make the assertion that a  
> specific property relationship is negated, and nothing else.

That works. In OWL 1.1 you can say it directly to, i.e.,:
	NegativeObjectPropertyAssertion(P, a, b)

(It's a a bit less pleasant in RDF/XML as you have to reify...here's  
hoping for better solutions. The abstract syntax and the XML syntax  
aren't so bad.

Also, the nominal form, well, requires nominals. Not all reasoners  
support them. A perhaps more flexible encoding in OWL 1.1 would be to  
use a dummy class and a qualified number restriction to 0 Ps to that  
class.)

> We've used this in our applications, so I'd like to know if we have  
> an incorrect understanding.

Only of my email, I think.

Hope this helps.

Cheers,
Bijan.
Received on Thursday, 16 August 2007 18:49:02 GMT

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