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Re: Nonstructural restrictions

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Fri, 28 Mar 2008 13:42:49 +0100
Cc: Alan Ruttenberg <alanruttenberg@gmail.com>, colombet@elet.polimi.it, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
Message-Id: <32AE527B-D934-41F1-9FD3-3D3D1B39B6C8@uva.nl>
To: Uli Sattler <sattler@cs.man.ac.uk>

Hi Uli,

On 28 mrt 2008, at 13:32, Uli Sattler wrote:
>
>> Hm. Your answer got me a bit confused.. Like Marco, I thought  
>> ObjectExistsSelf was not allowed on composed properties at all.
>
> ...and you thought correctly

pfew... glad to hear that!

>> Are you saying they *are* allowed on any class, or just owl:Thing?
>>
>
> no - all I am saying is that ObjectPropertyReflexive(P) is allowed  
> on a composite property, despite the fact that this is equivalent to  
> SubClassOf(owl:thing, ObjectExistsSelf(P)) -- but this equivalence  
> doesn't mean that
>
> (a) an ontology will contain the latter axiom or
> (b) a reasoner will have to be able to handle such axioms, or in  
> general ObjectExistsSelf(.) on composite properties...
>
> This equivalence only shows that ObjectPropertyReflexive(P) *can* be  
> viewed as a *special* of an axiom involving a ObjectExistsSelf(.) on  
> a composite property...

Ok, that really explains (Carsten's remark helped as well).

>> If so, I guess the description in the syntax document could use  
>> some clarification.
>
> ...do you think so? I would think that adding a note "yes indeed,  
> this is not a type/oversight" is perhaps useful, but I am not sure  
> we really want this explanation in there?

No, indeed. I was merely suggesting that if the Self restriction was  
allowed in special cases, that could be mentioned in the syntax doc.  
But as I now understand it, there is no such special case, rather some  
exception to the general rule, which has its own particular syntax.

Thanks again for the explanation,

-Rinke


>
>
> Cheers, Uli
>
>>
>>
>> -Rinke
>>
>>
>> On 27 mrt 2008, at 20:24, Uli Sattler wrote:
>>>
>>> On 27 Mar 2008, at 18:27, Alan Ruttenberg wrote:
>>>
>>>>
>>>>
>>>> Begin forwarded message:
>>>>
>>>>> Resent-From: public-owl-dev@w3.org
>>>>> From: "Marco Colombetti" <colombet@elet.polimi.it>
>>>>> Date: March 26, 2008 12:11:47 PM EDT
>>>>> To: <public-owl-dev@w3.org>
>>>>> Subject: Nonstructural restrictions
>>>>> Archived-At: <http://www.w3.org/mid/002e01c88f5c$18ecbb70$7c46fea9@lapcolombetti 
>>>>> >
>>>>>
>>>>> Hi.
>>>>>
>>>>> In http://www.webont.org/owl/1.1/owl_specification.html  “OWL  
>>>>> 1.1 Web Ontology Language - Structural Specification and  
>>>>> Functional-Style Syntax - Editor's Draft of 23 May 2007”.
>>>>>
>>>>> in Section 7 “Nonstructural Restrictions on Axioms”,
>>>>>
>>>>> I find that:
>>>>> 	• Only simple object properties are allowed to occur in Ax in
>>>>> 		• ObjectMinCardinality, ObjectMaxCardinality,  
>>>>> ObjectExactCardinality, and ObjectExistsSelf classes, and
>>>>> 		• ObjectPropertyFunctional,  
>>>>> InverseFunctionalObjectProperty,ObjectPropertyIrreflexive,  
>>>>> ObjectPropertyAsymetric, andDisjointObjectProperty axioms.
>>>>> I wonder whether composite properties should also be forbidden  
>>>>> in ObjectPropertyReflexiveaxioms, given that these are  
>>>>> equivalent toSubObjectPropertyOf(owl:Thing,ObjectExistsSelf(P)).
>>>>>
>>>
>>> good question:  ObjectPropertyReflexive(P) for a non-simple/ 
>>> composite property is ok. This might be a bit hard to see, but i  
>>> will try to explain. It is equivalent, as you say, to
>>>
>>> SubClassOf(owl:thing, ObjectExistsSelf(P)),
>>>
>>> but this is also ok: in principal, what is difficult for a  
>>> composite property, is
>>>
>>> SubClassOf(AClass, ObjectAllValuesFrom(P AnotherClass)),
>>>
>>> Ie, universal/all restrictions are difficult for them, but not  
>>> existential/some restrictions as in "ObjectExistSelf"....
>>>
>>> Cheers, Uli
>>>
>>>
>>>>> Regards,
>>>>>
>>>>> Marco Colombetti
>>>>>
>>>>>
>>>>
>>>
>>
>> -----------------------------------------------
>> Drs. Rinke Hoekstra
>>
>> Email: hoekstra@uva.nl    Skype:  rinkehoekstra
>> Phone: +31-20-5253499     Fax:   +31-20-5253495
>> Web:   http://www.leibnizcenter.org/users/rinke
>>
>> Leibniz Center for Law,          Faculty of Law
>> University of Amsterdam,            PO Box 1030
>> 1000 BA  Amsterdam,             The Netherlands
>> -----------------------------------------------
>>
>>
>>

-----------------------------------------------
Drs. Rinke Hoekstra

Email: hoekstra@uva.nl    Skype:  rinkehoekstra
Phone: +31-20-5253499     Fax:   +31-20-5253495
Web:   http://www.leibnizcenter.org/users/rinke

Leibniz Center for Law,          Faculty of Law
University of Amsterdam,            PO Box 1030
1000 BA  Amsterdam,             The Netherlands
-----------------------------------------------
Received on Friday, 28 March 2008 12:43:29 GMT

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