interface Sensor {
  enum Code { ok, nok };
  in Code activate();
  in void deactivate();
  behaviour { 

    on activate: reply(Code.ok);
    on activate: reply(Code.nok);
    on deactivate: {}
  }
}

interface Start {
  in void start();
  behaviour {
    on start: {}
  }
}

component Test {
  provides Start start;
  requires Sensor sensor;
  behaviour {
    on start.start(): sensor.activate(); 
  }
}