[boost] [TTI] Why add to boost namespace?

Why do the macros add templates to the boost::tti namespace rather than the current one? One thing I get from the way MPL create the has_xxx metafunctions is that I can do this: template < typename T > struct obeys_xxx_concept { BOOST_MPL_HAS_XXX_TRAIT_DEF(some_trait) ... etc... enum { value = etc_checks<T>(0).... && has_some_trait<T>::value }; typedef boost::mpl::bool_<value> type; }; That wouldn't work with the TTI library it appears. What does putting the templates in the boost::tti namespace do for me to make up for this loss?