CODEWITHSUNDEEP
ontologysemantic-webprotege
Travis
Travis

Reputation: 13

How would you model that a potential relationship exists between two classes, but doesn't always?

I want to model that something may be, but is not guaranteed, to be true. For example, a house may have a garage, but not necessarily. And a garage may be part of a house, but not necessarily.

If I add as an axiom "has_part some 'garage'" to my 'house' class, I'm claiming that all houses have garages, which isn't always true. Similarly, I can't add "partOf" to my garage class for the same reaosn.

What would be the ideal way to model this relationship?

I've tinkered with declaring that the class 'house' "has_part some 'garage' min 0" in order to use cardinality to set the minimum bound to zero, but I'm not sure that's correct.

Upvotes: 1

Views: 47

Answers (1)

Henriette Harmse
Henriette Harmse

Reputation: 4787

In that case you you can think of the class House consisting of two different classes: (1) the class of houses that do not have garages and (2) the class of houses that do have garages.

You could do this in Manchester syntax as follows:

 Class: ClassWithoutGarage
    SubClassOf: hasGarage max 0 Thing //has no garage

 Class: ClassWithGarage
    SubClassOf: hasGarage min 1 Thing
    DisjointWith: ClassWithoutGarage //has at least 1 garage

 ObjectProperty: hasGarage
    Domain: ClassWithGarage
    Range: Garage

 Class: House 
   EquivalentTo: ClassWithGarage or ClasWithoutGarage

In this case we have given explicit names to these 2 possible classes. Often in ontologies, the existence of these classes can be implied without explicitly naming them:

Class: House
   EquivalentTo: hasGarage max 0 Thing 
                 or  
                 hasGarage min 1 Thing

which can be stated more concisely with

Class: House
    EquivalentTo: hasGarage only Garage

hasGarage only Garage defines the class of individuals consisting of those individuals x such that when individual y is linked via hasGarage to individual x, then y is of type Garage, or those individuals x that has no link via hasGarage.

Upvotes: 0

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