assertion  retraction  graph  subject    predicate        object     datatype    annotation
1          0           graph  DOID:1518  oio:id           DOID:1518  xsd:string  
1          0           graph  DOID:1517  rdfs:subClassOf  DOID:1518  _IRI        
1          0           graph  DOID:1521  rdfs:subClassOf  DOID:1518  _IRI