text: symmetric properties. If Michelle hasSpouse Barack, then Barack hasSpouse Michelle. A 
  symmetric property is its own inverse. 
  
  An Asymmetric property is a property that can never have symmetric values. If a property P is 
  asymmetric then if a is related to b via that property b cannot be related to a via that property. An example 
  of an asymmetric property is hasBirthMother. If Diya hasBirthMother Fatima, then it can’t be the 
  case that Fatima hasBirthMother Diya. 
  
  4.8.5 Reflexive and Irreflexive Properties 
  A reflexive property is a property that always relates an individual to itself. If a property P is reflexive 
  then for all individuals a P will always relate a to a. Equality is the most common example of a reflexive 
  property. For any object a, a is always equal to a. An irreflexive property is… you guessed it… a property 
  that can never relate an individual to itself. The property hasBirthMother is an example of an 
  irreflexive property since no person can be their own mother. Note: you should use reflexive properties 
  with care. The domain of a reflexive property is*always*owl:Thing. The reasons are complex, see the 
  W3C Owl 2 Specification in the bibliography for more details. The important thing is that if you make a 
  property reflexive that means its domain is owl:Thing. For example, if you have a reflexive property 
  and declare its domain to be some class such as Person the reasoner will infer that Person is equivalent 
  to owl:Thing which can cause problems. 