@prefix owl: <http://www.w3.org/2002/07/owl#>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix : <foo://bla/names#>.

:Person a owl:Class .
:kate a owl:NamedIndividual; a :Person; :name "Kate"; :child :john.
:john a owl:NamedIndividual; a :Person; :name "John"; :child :alice.
:alice a owl:NamedIndividual; a :Person; :name "Alice".

:child a owl:ObjectProperty;
       rdfs:domain :Parent;
       owl:inverseOf :parent.
:parent a owl:ObjectProperty.

:Parent a owl:Class;
  owl:equivalentClass
    [a owl:Restriction; owl:onProperty :child; owl:minCardinality 1].