assertion  retraction  graph  subject    predicate        object     datatype    annotation
1          0           graph  DOID:7521  oio:id           DOID:7521  xsd:string  
1          0           graph  DOID:7520  rdfs:subClassOf  DOID:7521  _IRI        
1          0           graph  DOID:8068  rdfs:subClassOf  DOID:7521  _IRI