@prefix ex: <http://example.org/example#> . 
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . 
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . 
@prefix owl: <http://www.w3.org/2002/07/owl#> . 

 _:o rdf:type owl:Ontology .
 ex:A rdfs:subClassOf ex:B .