assertion  retraction  graph  subject    predicate        object    datatype    annotation
1          0           graph  DOID:1975  rdfs:subClassOf  DOID:533  _IRI        
1          0           graph  DOID:533   oio:id           DOID:533  xsd:string  
1          0           graph  DOID:3277  rdfs:subClassOf  DOID:533  _IRI