@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix owl: <http://www.w3.org/2002/07/owl#>.
@prefix : <foo:bla#>.
:q a owl:FunctionalProperty.
:p a owl:ObjectProperty; rdfs:domain :D.
:D owl:equivalentClass [ a owl:Restriction; owl:onProperty :p;
                                            owl:maxCardinality 1 ].
# :x :p :a, :b.    :a owl:differentFrom :b.