interface ihello
{
  in void hello();
  out void world();

  behaviour
  {
    on hello: {}
    on inevitable: world;
  }
}

component hello_inevitable_action
{
  provides ihello h;
  requires ihello w;

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