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[protege-owl] Define more than Subject-Predicate-Object

Timothy Redmond tredmond at stanford.edu
Sun Apr 29 22:47:34 PDT 2007


On Apr 27, 2007, at 1:30 PM, Steve Jonathan Tirtha wrote:

> Hi,
>
> After studying OWL, I see, that OWL can only represent a statement/ 
> knowledge in S-P-O(Subject-Predicate-Object).
> Can I also define S-P-O-Context. I don't know the right term, so I  
> call it "Context".
> Example: S-P-O
>                    - Person signs Contract
>                    - Michael signs LicenseAgreementNr.12
>                S-P-O-Context
>                    - Person signs Contract on [Time Context]
>                    - Michael signs LicenseAgreementNr. 12 on August  
> 12th 2006
>
> [Time Context] defines when a person signs a contract.

I think that the issue you are getting at is the problem described in  
http://www.w3.org/TR/swbp-n-aryRelations/.  This is a known problem  
and that web page gives a couple of approaches for solving the problem.

>
> I think, OWL can't represent  more than S-P-O.
>

This is a little subtle.  The statement you made is quite reasonable  
for the RDF language.  So one could argue that since OWL has a  
semantics based on the RDF semantics (http://www.w3.org/TR/owl- 
semantics/rdfs.html) the statement that you made also applies to  
OWL.  This is a defensible position.

However I would argue that this is not an entirely natural  
viewpoint.  Say we look at a statement like

	MyFavoritePizza = Pizza and (hasTopping some SausageTopping) and  
(hasBase all ThinAndCrispyBase).

It is possible to express the semantics  of such a statement in terms  
of triples.  But I would argue that the more natural semantics is the  
direct model  theoretic semantics (http://www.w3.org/TR/owl-semantics/ 
direct.html).  There is no need to turn this statement into a  
collection of triples in order to understand its meaning.

-Timothy






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