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[protege-owl] Why not define a class as the set of all entities with porperty x?

Timothy Redmond tredmond at stanford.edu
Tue Oct 28 01:43:55 PDT 2008


> Please let me know why you say it is generally not a good idea to  
> define a class via a propery as in 'A = (p has x)'.

This always comes down to a question of meaning.  If 'A = (p has x)'  
is exactly what you mean then this is how the definition should be  
written.  The trouble is that sometimes such statements are too strong  
- they need to be bounded.  So it may be that an assertion like

	A = B that (p has x)

is what you really wanted.  This is less extreme for the existential  
restrictions than for the universal restrictions.  Thus

	A = p all C

is almost always an incorrect definition.   It means in particular  
that if an individual has no p property value then that individual is  
in A.

-Timothy


On Oct 23, 2008, at 1:19 PM, Patrick McCrae wrote:

> Thanks for your response, Timothy.
>
> Please let me know why you say it is generally not a good idea to  
> define a class via a propery as in 'A = (p has x)'.
>
> I am asking because in my ontology I have defined several helper  
> classes in this way and am accessing their inferred contents via the  
> OWL API.
>
> Thanks and regards -
>
> Pat
> _______________________
>
> Patrick McCrae
>
> CINACS Graduate Research Group
> Department of Informatics
> Hamburg University
> Vogt-Kölln-Straße 30
> 22527 Hamburg, Germany
>
> patrick.mccrae at informatik.uni-hamburg.de
> fon: +49 . 40 . 428 83 - 23 60
> fax: +49 . 40 . 42883 - 2515
>
>
> Timothy Redmond wrote:
>>
>>
>>> I was now hoping that when I create an instance of the above  
>>> class, that instance would have the very same property. This,  
>>> however, turned out not to be the case. It seems that such class  
>>> properties are not propagated by inheritance.
>>
>> How did you conclude this?  I may have misunderstood but this is  
>> something that a reasoner can deduce.
>>
>> To make sure that I am understanding, let me give an example.  I  
>> can do this example in Protege 4.  Let's say that I have a class A,  
>> an object property p and an individual, x.  I make a definition
>>
>>     A = (p has x).
>>
>> (This is not generally a very good definition but that is another  
>> story).  Now I add an individual y in the class A.  I select a  
>> reasoner (pellet, say) and select classify.  In the individuals  
>> tab, I select the individual y and then under Object Property  
>> Assertions, I will see a highlighted item " p x ".  This  
>> highlighted item says that x is a p-value of y.  The fact that it  
>> is highlighted means that this was one of the things that the  
>> reasoner inferred.
>>
>> -Timothy
>>
>>
>>
>> On Oct 1, 2008, at 1:54 PM, Patrick McCrae wrote:
>>
>>> Dear Protege List -
>>>
>>> Can anyone please help me with the following modelling question  
>>> today:
>>>
>>> In Protege 4 I have created a class which is defined by the property
>>> has_Lexicalisation value Lex_word.
>>> This is analogous to
>>> has_Lexicalisation has Lex_word
>>> in the Protege 3.x world.
>>>
>>> I was now hoping that when I create an instance of the above  
>>> class, that instance would have the very same property. This,  
>>> however, turned out not to be the case. It seems that such class  
>>> properties are not propagated by inheritance.
>>>
>>> I am hence wondering how I can inherit properties of the above  
>>> kind from the class to its individuals.
>>>
>>> Thanks in advance for your help!
>>>
>>> Best regards -
>>>
>>> Pat
>>> _______________________
>>>
>>> Patrick McCrae
>>>
>>> CINACS Graduate Research Group
>>> Department of Informatics
>>> Hamburg University
>>> Vogt-Kölln-Straße 30
>>> 22527 Hamburg, Germany
>>> _______________________________________________
>>> protege-owl mailing list
>>> protege-owl at lists.stanford.edu
>>> https://mailman.stanford.edu/mailman/listinfo/protege-owl
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>>




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