assertion  retraction  graph  subject    predicate        object     datatype    annotation
1          0           graph  DOID:6018  rdfs:subClassOf  DOID:6015  _IRI        
1          0           graph  DOID:6016  rdfs:subClassOf  DOID:6015  _IRI        
1          0           graph  DOID:6015  oio:id           DOID:6015  xsd:string