assertion  retraction  graph  subject    predicate        object     datatype    annotation
1          0           graph  DOID:3721  rdfs:subClassOf  DOID:6536  _IRI        
1          0           graph  DOID:6536  oio:id           DOID:6536  xsd:string  
1          0           graph  DOID:9513  rdfs:subClassOf  DOID:6536  _IRI