text: 
  // Standard library:
  #include <iostream>
  #include <fstream>
  
  /// Third Party:
  // - Boost:
  #include <boost/serialization/nvp.hpp>
  #include <boost/archive/xml_oarchive.hpp>
  
  // Ourselves:
  #include <Z/Z.hpp>
  #include <Z/Z-serial.ipp>
  
  int main(void)
  {
    std::ofstream file("test_Z.xml");
    boost::archive::xml_oarchive oa(file);
    xy::X x(666);
    xy::Y y(xy::X(12));
    z::Z  z(y, x);
    std::clog << "z = " << z << std::endl;
    oa & BOOST_SERIALIZATION_NVP(z);
    return 0;
  }
  