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Re: [ontolog-forum] Common Logic Controlled English (CLCE)

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From: Florian Probst <f.probst@xxxxxxxxxxxxxxx>
Date: Mon, 19 Mar 2007 14:44:30 +0100
Message-id: <45FE93BE.5050504@xxxxxxxxxxxxxxx>
hi,
in this thread and in the "Ontology and methodology" thread the category 
ROLE was mentioned several times.
I am wondering what a role is ontologically? What are the 
super-categories of ROLE? In one of the extensions of DOLCE, a role is 
considered a non-physical social object.
Roles seem helpful in terms of achieving taxonomically "clean" 
ontologies in the sense of OntoClean (Welty, Guarino).
Yet employing the category ROLE in ontology engineering seems to be 
problematic since many (most) categories used in domain ontologies would 
suddenly have ROLE as super-category. What do I get wrong here?
Take for example an object that is identified as being a chair. I guess 
in many ontologies, CHAIR would be classified as sub-category of 
PHYSICAL OBJECT. This is, any entity that is identified to be a chair is 
also a physical object.
However, in the context of the previous mails, one could claim that a 
chair is identified being a chair by affording sitting on it; by the 
role it plays. If a certain entity which was previously identified as 
chair, is never used again for sitting but only for, say, a step for 
changing light bulbs, it stops playing the role of being a chair and is 
hence only playing the role of a step for changing light bulbs (?). 
Compare this to an employee being fired. The person does not loose its 
ability of playing the role of an employee, yet the certain entity is 
not classified as employee anymore.
Why should a physical object, that is never used for sitting be 
considered a chair?
Why should employee be a role while chair is not?    (01)

best regards,
Florian    (02)





John F. Sowa wrote:
> Dear Matthew,
>
> I agree that the distinction is essential, but that approach
> makes it difficult to express all necessary constraints:
>
>   
>> MW: Actually it was a modelling principle, that entity types should be
>> based on the underlying nature of a thing rather than a role that it
>> plays.
>>
>> MW: Following this approach relations were also modelled as entity types
>> and roles were modelled on the relationships (E-R sense) linking the
>> relations to the domains of the things they related.
>>     
>
> But I put all types in a single hierarchy, in which all roles are
> under the type Role.  Since the hierarchy is a lattice, it allows
> all possible combinations, such as MaleEmployee or PregnantEmployee.
>
> This approach makes it possible to state constraints on
> permissible relationships very conveniently.  For example,
> a relationship that is restricted to PregnantEngineerEmployee
> can be hard to represent in a typical E-R diagram.
>
> John
>  
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>       (03)


-- 
http://ifgi.uni-muenster.de/~probsfl
GI-Days 2007 "Young Researchers Forum": http://www.gi-days.de    (04)



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