Hi, I am a bit confused about the purpose of GUID. My understanding was, that it is a user defined id for a class, so that the serialization mechanism knows what types to instanciate on load. I somehow assumed it to be a replacement (or equivalent) of the numbers in the class_id attributes. by inserting: BOOST_CLASS_EXPORT_GUID( bus_schedule, "BusSchedule" ); I'd expected to find something like: <schedule class_id="BusSchedule" in the xml file, but I get only: <schedule class_id="1" I know that another purpose of the BOOST_CLASS_EXPORT family of macros is to instanciate the <Archive, T*> pairs, but what is the "BusSchedule" string then for. If my assumption was right, where do I have to place the macros exactly then. I tried at the end of the header with the classes. I then tried at the beginning, after the includes. That didn't work unless I forward declared the classes (no surprise really). Also, is there some docs/tutorials/further reading on xml archives. I am probably going to make my own archive, and need to understand more about the mechanism. Thanks for your help, Ingo