@prefix owl: <http://www.w3.org/2002/07/owl#>.
@prefix : <foo://bla#>.
:Childless owl:intersectionOf (:Person
  [ a owl:Restriction; owl:onProperty :hasChild; owl:maxCardinality 0]).
:Parent owl:intersectionOf (:Person
  [ a owl:Restriction; owl:onProperty :hasChild; owl:minCardinality 1]).
:john a :Person; :hasChild :alice, :bob.
:alice a :Person.  :bob a :Person.