Protege OWL DataProperty on ObjectProperty

Question

I am trying to express this one:

Manchester distance from London is 335 km.

I have created class city and now I am thinking to create and objectProperty hasDistance with Domain City and Range City.

But where can I declare the real distance for it?

Answer 1

This is in actual fact an example of an n-ary relation. In such a case the relation is modelled as a class rather than a property. For this purpose, let us assume we introduce a class DistanceBetweenTwoCities. Hence, one way to model this is as follows:

Class: City
Class: DistanceBetweenTwoCities

ObjectProperty: hasCity1
    Domain: DistanceBetweenTwoCities    
    Range: City

ObjectProperty: hasCity2
    Domain: DistanceBetweenTwoCities
    Range: City

DataProperty: hasDistance
    Domain: DistanceBetweenTwoCities
    Range: xsd:integer

To now state the distance between London and Manchester:

Individual: distanceLondonToManchester
    Types: 
    DistanceBetweenTwoCities

    Facts:  
     hasCity1  london,
     hasCity2  manchester,
     hasDistance  335


Individual: london
    Types: City

Individual: manchester
    Types: City

Note: Strictly speaking it is not necessary to introduce two different properties hasCity1 and hasCity2. We could have used only hasCity. I only introduced 2 properties to make the n-ary relation a bit more obvious.

Update 20190320

If you have another distance you have to present you can add another individual of type DistanceBetweenTwoCities:

Individual: distanceLondonToAthens
    Types: 
    DistanceBetweenTwoCities

    Facts:  
      hasCity1  london,
      hasCity2  athens,
      hasDistance  3000


Individual: athens
     Types: City