Simple Reflection

I am using boost serialization to serialize types to/from xml files. This is working great but I still have to define an instance of the type: SomeClass someClass; boost::serialization::xml_iarchive archive(someFileStream); archive >> someClass; I'd really just like to load the file and the loader to "know" the type based on a tag in the xml file. Is there a relatively simple way to do this without implementing an extensive reflection system? Thanks