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Re: Can an object property be both functional and transitive?

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Mon, 26 Jan 2009 19:50:53 +0000
Message-Id: <D1B2B845-A2DB-4776-AA80-8CCA1C860FF1@cs.man.ac.uk>
To: W3C OWL Working Group <public-owl-wg@w3.org>

On 26 Jan 2009, at 19:36, Jie Bao wrote:
>
> I come across this issue when update the Quick Reference. This issue
> may already have been discussed, as I was not in the WG from the very
> beginning. I just need a confirmation.
>
> In OWL 1 DL, This is not allowed, for decidability considerations.
> http://www.w3.org/TR/owl-semantics/syntax.html#2.3.2.4
>
> In OWL 2 DL, it is allowed, i.e., an object property CAN be both
> functional and transitive
> http://www.w3.org/2007/OWL/wiki/Syntax#Object_Property_Axioms  
> (Figure 15)

No. See the global restrictions:
	http://www.w3.org/2007/OWL/wiki/Syntax#Global_Restrictions_on_Axioms

"""Each axiom in Ax of a type from the following list contains an  
object property expression that is simple in Ax:
FunctionalObjectProperty, InverseFunctionalObjectProperty,  
IrreflexiveObjectProperty, AsymmetricObjectProperty, and  
DisjointObjectProperties."""

> As far as I can guess, this may reflect the recent progress on
> undecidability results of DL with number restrictions.
>
> Yevgeny Kazakov, Ulrike Sattler, and Evgeny Zolin. How many legs do I
> have? Non-simple roles in number restrictions revisited. In Proc. of
> the 14th Int. Conf. on Logic for Programming, Artificial Intelligence,
> and Reasoning (LPAR'2007), Yerevan, Armenia October 15-19, 2007.
> http://www.cs.man.ac.uk/~ezolin/pub/zolin_2007_RBox.pdf
[snip]
> Since OWL 2 has  inverse properties (role), is there any restriction
> on its use to ensure the decidability of OWL 2 DL?

Since that condition is even more complex, I'm not sure it's a good  
idea to add it at this time. (Simple vs.  non-simple is much easier.)  
I do hope implementations will go beyond the coarser restriction over  
time.

Cheers,
Bijan.
Received on Monday, 26 January 2009 19:47:28 GMT

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