question: Was M1 directed by M2 , directed by a actor , directed by M3 , and directed by M4
query: SELECT count(*) WHERE {
  ?x0 a ns:film.actor .
  M1 ns:film.film.directed_by ?x0 .
  M1 ns:film.film.directed_by M2 .
  M1 ns:film.film.directed_by M3 .
  M1 ns:film.film.directed_by M4
  }