PREFIX :       <http://example.org/>
PREFIX schema: <http://schema.org/>
PREFIX xsd:    <http://www.w3.org/2001/XMLSchema#>

:User IRI {
  schema:name          xsd:string  ;
  schema:birthDate     xsd:date?  ;
  schema:gender        [ schema:Male schema:Female ] ;
  schema:knows         @:User* 
}