text: 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 
  
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