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Re: Reflexivity and antisymmetry uses cases?

From: Michael Schneider <m_schnei@gmx.de>
Date: Mon, 22 Jan 2007 15:22:41 +0100
Message-ID: <45B4C8B1.4040109@gmx.de>
To: Evren Sirin <evren@clarkparsia.com>
CC: holger@topquadrant.com, public-owl-dev@w3.org

Thanks, Evren!

So, I see now, that my second example for antisymmetric and /ireflexive/ 
relations, the "locatedIn" property between geographical regions, should 
be better modeled to actually be locally /reflexive/, because every 
region is located within itself. This is, of course, an important usecase.

So, technically, this would then be specified the following way, right?

   ObjectProperty(locatedIn
     type(AntisymmetricProperty)
     type(TransitiveProperty)
   )

   Class(GeographicalRegion partial
     selfRestriction(locatedIn)
   )

Cheers,
Michael

Evren Sirin wrote:
> On 1/20/07 9:44 AM, Michael Schneider wrote:
>>
>> Holger Knublauch wrote on Wed, 17 Jan 2007:
>>
>>>  I don't remember a lot of requests for something
>> > like owl:SelfRestriction on our mailing lists.
>>
>> And AFAICS, nobody here in this thread has given an example for 
>> SelfRestrictions, yet. I thought about it yesterday evening for a 
>> while, but could not come up with any serious example. Well, besides 
>> this standard toy class of "SelfLovers", wherein property "loves" is 
>> thought to behave transitively. ;-)
>>
>> It's easier for me to imagine that antisymmetry and ireflexivity could 
>> become important, because, in combination with transitivity, I am able 
>> to more precisely model all kinds of partial orderings between 
>> instances, like e.g. ancestor relationships between people or events, 
>> or inclusion relationships like "locatedIn"/"containedIn" between 
>> geographical regions.
>>
>> But where is the "killer application" for owl11:SelfRestriction?
> I'm not sure if you are only referring to SelfRestriction (local 
> reflexivity) or ReflexiveProperty (global reflexivity) in general. I 
> think it was mentioned earlier that reflexivity is used to describe 
> part/whole relationships [1]. I don't know if this would be the "killer 
> application" for reflexivity but it is certainly a widely used one. If 
> you are asking about why we would want to use SelfRestriction instead of 
> ReflexiveProperty then I can give a real-world example explaining this:
> 
> One might be inclined to define foaf:knows property to be a 
> ReflexiveProperty (similar to your loves example) because you want to 
> model that every foaf:Person knows himself/herself. However, adding this 
> innocent looking statement to FOAF vocabulary would make concept such as 
> foaf:Document, foaf:Organization, foaf:Project unsatisfiable and any 
> FOAF description that describes instances of these concepts would end up 
> to be inconsistent. The reason is simple: When you say a property is a 
> ReflexiveProperty then every individual in the universe should have that 
> property. This means if you have an instance of foaf:Document, say 
> MyDocument, then we infer that MyDocument knows itself. But the 
> domain/range restrictions on foaf:knows says only foaf:Person's can have 
> foaf:knows property. Since foaf:Document is disjoint with foaf:Person 
> this would be a contradiction. The right thing to do in this case would 
> be to use SelfRestriction construct to define a local reflexivity axiom 
> for foaf:Person.
> 
> Regards,
> Evren
> 
> [1] http://www.w3.org/2001/sw/BestPractices/OEP/SimplePartWhole/
>>
>> Michael
>>
>>
> 
Received on Monday, 22 January 2007 14:22:53 GMT

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