private Batch <Actor> talksTo() {
    final Batch <Actor> batch = new Batch <Actor> () ;
    if (subject instanceof Actor) {
      final Actor a = (Actor) subject ;
      batch.add(a) ;
    }
    else if (subject instanceof Venue) {
      final Venue v = (Venue) subject ;
      for (Actor a : v.personnel.residents()) batch.include(a) ;
      for (Actor a : v.personnel.workers()  ) batch.include(a) ;
    }
    return batch ;
  }