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[protege-owl] Modelling decision between 'annotation property' and 'class definition restriction'

Thomas Russ tar at ISI.EDU
Wed Oct 29 09:26:16 PDT 2008

On Oct 29, 2008, at 2:36 AM, Patrick McCrae wrote:

> Thanks, Timothy!
> I see things are getting much clearer now. Basically, then the  
> decision whether to include my property 'has_Lexicalisation' as an  
> annotation property or a class definition restriction is a modelling  
> decision I have to take based on the requirements of my ontology  
> usage. From what you are saying I conclude that any property which  
> does not affect the reasoning process can in principle be modelled  
> as an annotation property to a class.

Maybe or maybe not.

The real distinction is whether the property value you are talking  
about is a property of the class itself, or a property of individuals  
who are instances of that class.

Consider two possible different semantics for an "author" property.   
One of them describes the person who creates a class in the knowledge  
base.  The other is a domain relation indicating who wrote some item  
in the domain.


       Class:  RedWine  author Tom

This means that Tom wrote (created) the class RedWine.  It doesn't say  
anything about individuals of type RedWine.  It is a meta-annotation  
because the reasoner doesn't look at it when trying to infer anything  
about individuals of RedWine. (Presumably, with meta-level reasoning  
one could define the meta-class of classes that Tom created, but IIRC  
that takes you outside OWL-DL).  Now this same meta-annotation could,  
in theory, also be applied to individuals, if you wanted to track who  
created the instance SwallowCreekMerlot1999 with type RedWine.  But it  
wouldn't be part of the definition of the class RedWine, since it  
applies only to that particular individual rather than to all  
individuals of the class RedWine.


       Class:  SeussBook  <=>  Book and (has author DrSeuss)

This means that all individuals of the class SeussBook have DrSeuss as  
the author.  The classifier uses this information to infer a filler of  
the author field for any books asserted to have type SeussBook.  It  
also uses this same information to infer that any books written by Dr.  
Seuss are Seuss books.

So, the modeling decision really comes down to what it is you want to  
say about the property.  Is it a property that applies to the class  
object itself, or does it apply to individuals of that class.

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