assertion  retraction  graph  subject   predicate        object    datatype    annotation
1          0           graph  DOID:332  rdfs:subClassOf  DOID:231  _IRI        
1          0           graph  DOID:231  oio:id           DOID:231  xsd:string  
1          0           graph  DOID:681  rdfs:subClassOf  DOID:231  _IRI