interface ihello
{
  in void hello();

  behaviour
  {
    on hello: {}
  }
}

component foreign
{
  provides iworld w;
  // behaviour {}
}

component hello
{
  provides ihello h;
  requires iworld w;

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

interface iworld
{
  in void world();

  behaviour
  {
    on world: {}
  }
}

component hello_foreign
{
  provides ihello h;

  system
    {
      hello c;
      foreign f;
      h <=> c.h;
      c.w <=> f.w;
    }
}