Forward объявляет интерфейсы мономорфных наборов данных.

namespace boost {
  namespace unit_test {
    namespace data {
      template<typename DataSet> 
        std::enable_if< monomorphic::is_dataset< DataSet >::value, DataSet >::type 
        make(DataSet &&);
      template<typename T> 
        std::enable_if<!is_forward_iterable< T >::value &&!monomorphic::is_dataset< T >::value &&!is_array< typename remove_reference< T >::type >::value, monomorphic::singleton< T > >::type 
        make(T &&);
      template<typename C> 
        std::enable_if< is_forward_iterable< C >::value, monomorphic::collection< C > >::type 
        make(C &&);
      template<typename T, std::size_t size> 
        monomorphic::array< typename boost::remove_const< T >::type > 
        make(T(&));
      monomorphic::singleton< char * > make(char *);
      monomorphic::singleton< char const * > make(char const *);
      template<typename T> 
        monomorphic::init_list< T > make(std::initializer_list< T > &&);
      namespace monomorphic {
        template<typename DataSet> struct is_dataset;
        template<typename DataSet> struct is_dataset<DataSet &>;
        template<typename DataSet> struct is_dataset<DataSet const>;
      }
      namespace result_of {
        template<typename DataSet> struct make;
      }
    }
  }
}