Hello, I made a minor change in the type registration mechanism from using macros to this: struct my_tag: boost::exception_info_tag<int> { }; This update addresses the issue of being able to register tags in user-defined namespaces. The updated documentation and source code can be found at http://www.revergestudios.com/boost-exception/boost-exception.html It is also possible to extend the interface to support enumeration of the exception info stored in boost::exception objects, but my personal preference is to first collect more feedback from people using the library, because I'm not sure if this enumeration is needed in practice. Brad King illustrated this idea in his earlier post: http://article.gmane.org/gmane.comp.lib.boost.devel/146322 I've also received feedback that boost::exception_info would be used fairly often and needs a shorter name. Maybe boost::xinfo? I hope someone comes up with a better name. Finally, I would ask everyone who provided feedback before to please use the mailing list for that. Having an open discussion is important. Thanks, Emil Dotchevski