Lets say we wanted boost/detail to depend on nothing but config, here's what it would take: boost/detail/algorithm.hpp Used by graph lib only, suggest it's moved there. boost/detail/allocator_utilities.hpp Used by multi index, statechart and flyweight, suggest move to new "common" module. boost/detail/atomic_count.hpp Depends on smart_ptr's details only, suggest those details are moved to "detail" module. boost/detail/binary_search.hpp Used by python and test, move to "common". boost/detail/bitmask.hpp Only external dependency is boost/cstdint.hpp, either move to "common", or else move cstdint.hpp to "config". boost/detail/call_traits.hpp Move to call_traits (should be there already). boost/detail/catch_exceptions.hpp Only external dependency is boost/cstdint.hpp, suggest latter is moved to config. boost/detail/compressed_pair.hpp Move to compressed pair (should be there already). boost/detail/endian.hpp Move to "predef" boost/detail/has_default_constructor.hpp File appears to be unused, and not very useful, suggest we remove it. boost/detail/identifier.hpp File appears to be unused, suggest we remove it. boost/detail/indirect_traits.hpp Used by iterator and python, move to "common" boost/detail/is_incrementable.hpp Move to common, or better modify the libraies using this to use the newer type_traits equivalents. boost/detail/is_sorted.hpp Used by graph and range, move to "common" boost/detail/is_xxx.hpp Used by parameter and python, move to "common" boost/detail/iterator.hpp I suspect this may be obsolete now compiler requirements have been bumped, but whatever it's still used by multiple libs: move to "common" boost/detail/lcast_precision.hpp Only used by lexical_cast, move it there. boost/detail/lightweight_mutex.hpp Only extern dependency is smart_ptr's details, suggest move those to detail. boost/detail/named_template_params.hpp Appears to be unused, suggest we remove. boost/detail/numeric_traits.hpp Used by graph and iterator, move to "common" boost/detail/ob_compressed_pair.hpp Move to compressed pair, might also be obsolete by now. boost/detail/quick_allocator.hpp Only external dependency is smart_ptr's details, suggest those are moved here. Or since only serialization uses this, move this file there... boost/detail/reference_content.hpp Used by optional and variant, move to "common". boost/detail/winapi/* Depends on boost/cstdint.hpp only, suggest that belongs to config. Everything else in detail has no dependencies other than config. Thoughts? John.