text: 4.10.2 Existential Restrictions 
  An existential restriction describes a class of individuals that have at least one (some) relationship along a 
  specified property to an individual that is a member of a specified class or datatype. For example, 
  hasBase some PizzaBase describes all of the individuals that have at least one relationship along the 
  hasBase property to an individual that is a member of the class PizzaBase — in more natural English, 
  all of the individuals that have at least one pizza base. 