assertion  retraction  graph  subject    predicate        object     datatype    annotation
1          0           graph  DOID:1519  rdfs:subClassOf  DOID:1521  _IRI        
1          0           graph  DOID:1522  rdfs:subClassOf  DOID:1521  _IRI        
1          0           graph  DOID:1521  oio:id           DOID:1521  xsd:string