24 
 
3. Select isIngredientOf  and then Tools>Create object property hierarchy. Enter isToppingOf then on a 
new line enter isBaseOf. As before, select Continue and leave the box for disjoint properties unchecked 
and select Finish. Repeat step 2 to make isToppingOf the inverse of hasTopping and isBaseOf the 
inverse of hasBase.  
4. Synchronize the reasoner. Your window should now look like figure 4.12.  
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Figure 4.12 Inverse Properties 
 
4.8 OWL Object Property Characteristics   
OWL allows the meaning of properties to be enriched through the use of property characteristics. The 
following sections discuss the various characteristics that properties may have. If you are familiar with 
basic concepts of relations in set theory these characteristics will already be familiar to you. In figure 4.12 
you can see the Characteristics: view for a property as a list of check boxes: Functional, Inverse 
functional, Transitive, etc.  
4.8.1 Functional Properties 
If a property is functional, for a given individual, there can be at most one individual that is related to the 
individual via the property. For example the property hasBirthMother -- someone can only have one 
birth mother. If we say that the individual Jean hasBirthMother Peggy and we also say that the 
individual Jean hasBirthMother Margaret, then because hasBirthMother is a functional property, 
we can infer that Peggy and Margaret must be the same individual. This can happen in OWL because