interface ihello
{
  in bool hello();

  behaviour
  {
    bool b = true;
    on hello: reply(b);
    [b] on optional: b=!b;
  }
}

component hello_silent
{
  provides ihello hi;
  requires ihello wi;

  behaviour
  {
    on hi.hello(): {bool b = wi.hello(); reply(b);}
  }
}