text: In situations like the above example, a common mistake is to use an intersection instead of a 
  union. For example, CheeseTopping*and*VegetableTopping. Although CheeseTopping 
  and Vegetable might be a natural thing to say in English, this logically means something that 
  is simultaneously a kind of CheeseTopping and VegetableTopping. This is incorrect 
  because we have stated that CheeseTopping and VegetableTopping are disjoint classes 
  and hence no individual can be an instance of both. If we used such a definition the reasoner 
  would detect the inconsistency. 