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Re: Nonstructural restrictions

From: Uli Sattler <sattler@cs.man.ac.uk>
Date: Fri, 28 Mar 2008 12:32:23 +0000
Cc: Alan Ruttenberg <alanruttenberg@gmail.com>, colombet@elet.polimi.it, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
Message-Id: <56384022-EBCE-47CD-B522-8F9E5BE7669F@cs.man.ac.uk>
To: Rinke Hoekstra <hoekstra@uva.nl>


On 28 Mar 2008, at 08:17, Rinke Hoekstra wrote:

> Hi Uli,
>
> 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

> 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...


> 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?

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
> -----------------------------------------------
>
>
>
Received on Friday, 28 March 2008 12:30:39 GMT

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