I dont understand the char_type member typedef of the traits class. The functions that use it all seeem to be free functions which could change from e.g template<class Ptree> void read_xml(std::basic_istream<typename Ptree::char_type> &stream, Ptree &pt, int flags = 0); to template<class Ptree, class Char> void read_xml(std::basic_istream<Char> &stream, Ptree &pt,int flags = 0); without problems. That would remove one level of coupling wouldnt it? ........... Why are all ptree nodes the same type? Commonly a tree will have branch and leaf nodes. In the debug example there are two branch nodes and 4 leaf nodes, which means two empty lists . That is wasteful isnt it? ................ Is it necessary to make key a string. Could it not also be (say) an integer id? regards Andy Little