assertion  retraction  graph  subject    predicate        object    datatype    annotation
1          0           graph  DOID:520   oio:id           DOID:520  xsd:string  
1          0           graph  DOID:4510  rdfs:subClassOf  DOID:520  _IRI        
1          0           graph  DOID:8352  rdfs:subClassOf  DOID:520  _IRI