question: Did a star of M0 and M1 direct a film
query: SELECT count(*) WHERE {
  ?x0 ns:film.actor.film/ns:film.performance.film M0 .
  ?x0 ns:film.actor.film/ns:film.performance.film M1 .
  ?x0 ns:film.director.film ?x1 .
  ?x1 a ns:film.film
  }