Re: owl:TopObjectProperty in property chains?

On 26 Aug 2008, at 07:15, Jeff Thompson wrote:

>
> [1] shows how to rewrite the rule
> hasParent(x, y) ^ hasBrother(y, z) -> hasUncle(x, z)
> into the OWL 2 axiom:
> ObjectProperty: hasUncle SubPropertyChain: hasParent o hasBrother
>
> Is the universal property owl:TopObjectProperty allowed in a  
> property chain?

Hi Jeff,

due to the so-called 'regularity condition', owl:TopObjectProperty  
cannot occur in a subPropertyChain. The details are a bit tricky but,  
in a nutshell, if you have a statement where a property P (or its  
inverse) occurs in a subPropertyChain of a property Q, then Q (orr its  
inverse) cannot occur in a subPropertyChain of P.

>  In
> other words, suppose you have the OWL 2 axiom:
>
> ObjectProperty: childRelatedToBrother
>  SubPropertyChain: hasParent o owl:TopObjectProperty o hasBrother
>
> would that be the same as this rule:
> hasParent(x, y) ^ hasBrother(w, z) -> childRelatedToBrother(x, z)
>
> In other words, the parent of x does not need to be the same as the  
> brother of z.
>

Now this example looks very strange indeed: could you explain to us  
what the idea behind it is? Cheers, Uli

> - Jeff
>
> [1] Gasse, F., Sattler, U., & Haarslev, V. (2008). Rewriting Rules  
> into
> SROIQ Axioms. Proceedings of the 2008 International Workshop on
> Description Logics (DL-2008).
>
>
> P.S. Michael Schneider wrote me a detailed reply to an earlier  
> question
> which I'm still cogitating.
>
>