At present, we have three dependencies that we can easily cut and doing so will be very beneficial: 1. type_traits now depends on utility only because utility: <boost/utility/declval.hpp> from <boost/type_traits/common_type.hpp> from <boost/type_traits/detail/common_type_imp.hpp> from <boost/type_traits/is_copy_constructible.hpp> from <boost/type_traits/is_nothrow_move_assignable.hpp> from <boost/type_traits/is_nothrow_move_constructible.hpp> Since declval.hpp itself depends on type_traits (add_rvalue_reference), it can't go to core and the most logical place for it is type_traits itself. 2. utility depends on iterator because iterator: <boost/iterator.hpp> from <boost/operators.hpp> <boost/iterator/iterator_facade.hpp> from <boost/generator_iterator.hpp> boost/iterator.hpp can be moved to core in all its former glory (and probably replaced by a one-liner, using std::iterator.) generator_iterator.hpp perhaps needs to be moved to iterator. 3. mpl depends on detail because detail: <boost/detail/endian.hpp> from <boost/mpl/string.hpp> <boost/detail/lightweight_test.hpp> from <boost/mpl/aux_/test.hpp> That last one is just because lightweight_test.hpp hasn't been removed from Detail yet; let me know if I should do that. boost/detail/endian.hpp is just a forwarding header that includes <boost/predef/detail/endian_compat.h>. We should move it to Predef. Comments? Objections?