interface ihello {
  in void hello();
  behaviour {
    on hello: {}
  }
}

interface iworld {
  in void hello();
  out void world();
  behaviour {
    on hello: world;
  }
}

component hello_external_queuefull {
  provides ihello h;
  requires external iworld w;

  behaviour {
    on h.hello(): w.hello();
    on w.world(): w.hello();
  }
}