assertion  retraction  graph  subject   predicate        object    datatype    annotation
1          0           graph  DOID:268  rdfs:subClassOf  DOID:272  _IRI        
1          0           graph  DOID:272  oio:id           DOID:272  xsd:string  
1          0           graph  DOID:271  rdfs:subClassOf  DOID:272  _IRI