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Re: OWL DL extension question

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Wed, 11 Apr 2007 19:40:12 +0100
Message-Id: <344DC6A8-20D1-45AE-A415-A4C996AF61F9@cs.man.ac.uk>
Cc: Evren Sirin <evren@clarkparsia.com>, Owl Dev <public-owl-dev@w3.org>, Evan Wallace <evan.wallace@nist.gov>, Yevgeny Kazakov <ykazakov@cs.man.ac.uk>
To: <conrad.bock@nist.gov>

On 11 Apr 2007, at 18:54, Conrad Bock wrote:

> Evren,
>>> Was wondering if anyone is looking into whether this fragment can
>>> be added tractably to OWL DL (1.0):
>>>   (forall (x y z)
>>>      (if (and (P x y)
>>>               (R x z))
>>>          (S y z)))
>>> For example, the uncles of my children include all my brothers
>>> (P=children, R=brothers, S=uncles).
>> You can turn the antecedent into a property chain using the
>> inverse of P
>> and then use the standard complex role inclusions of OWL 1.1 as:
>> SubObjectPropertyOf(SubObjectPropertyChain(InverseObjectPrope
>> rty(children)
>> brothers) uncles)
> Great, thanks.
>> provided that the restrictions described at [1] are not violated.
> Do you happen to know if anyone has shown these to be the maximal
> restrictions, ie, any loosening of them will cause undecidability?  In
> particular, is the regularity restriction maximal?

Yevgeny Kazakov has done some work on this. He has shown that the  
restriction is not maximal (which is pretty obvious), and I believe  
that he has devised an alternative and strictly more general  
restriction. I have a feeling that there is even an undecidability  
result related to maximality, but I might have imagined that :-).

Yevgeny can no doubt tell you more.



> Conrad
> PS: I assume the first set of bullets are disjunctive, but the text
> doesn't say this explicitly.
Received on Wednesday, 11 April 2007 18:40:25 UTC

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