class MyMessage : public SerialisableObject
{
  // message members
  int myNumber_;
  std::string myString_;
  std::vector<MyOtherSerialisableObject> aBunchOfThingsIWantToSerialise_;

public:
  // ctor, dtor, accesors, mutators, then:

  virtual void Serialise(SerialisationStream & stream)
  {
    stream & myNumber_;
    stream & myString_;
    stream & aBunchOfThingsIWantToSerialise_;
  }
};

serialisable MyMessage
{
  int myNumber_;
  std::string myString_;
  std::vector<MyOtherSerialisableObject> aBunchOfThingsIWantToSerialise_;
};