module observer_subject
{
  interface Subject;

  interface Observer
  {
    void notifier(in Subject s);
  };


  typedef sequence<Observer> ObserverList;

  exception DejaAttache {};
  exception PasAttache {};

  interface Subject
  {
    void attach(in Observer o)
      raises (DejaAttache);
    void multiple_attach(in ObserverList l)
      raises (DejaAttache);

    void detach(in Observer o)
      raises (PasAttache);

    void provoc_modif();

  };

};