Hi I am facing a problem about serialization. There are several objects constructed from class base1. And I want to serialize/deserialize only the member attribute "m_nID" from these objects. That's why only class base is registered. My problem is that when I try to serialize the objects construct from class base1, error message "unregistered_class" is throwed. It doesn't have such problem if the class base doesn't inherented from class blackbox. As I know the class blackbox is also using boost library, but I don't which part it is using. I have tryed to use marco BOOST_CLASS_EXPORT_GUID(base, "Base") but seems not useful in this case. --------------------------------------------------------------------- class base: public blackbox { friend class boost::serialization::access; template<class Archive> void serialize(Archive &ar, const unsigned int /* file_version */){ ar & boost::serialization::make_nvp("ComponentID", m_nID); } .... private: unsigned int m_nID; }; class base1: public base { //friend class boost::serialization::access; //template<class Archive> //void serialize(Archive &ar, const unsigned int /* file_version */){ // ar & boost::serialization::make_nvp("ComponentID", m_nID); // ar & boost::serialization::make_nvp("BaseInt", m_nBInt); // } .... }; Regards Barr Ng _________________________________________________________________ Learn English via Shopping Game, FREE! http://www.linguaphonenet.com/BannerTrack.asp?EMSCode=MSN06-03ETFJ-0211E