DATAFLOW_TRAITS(Type, Traits)
DATAFLOW_TRAITS_ENABLE_IF(Type, Cond, Traits)

namespace boost {
  namespace dataflow {
    template<typename Tag> struct traits;
    template<typename Traits, typename Enable = detail::enable_guard> 
      struct is_traits;
    template<typename T, typename Tag = default_tag, typename Enable = void> 
      struct traits_of;
    template<typename T, typename Tag = default_tag, typename Enable = void> 
      struct register_traits;
    template<typename T, typename Tag = default_tag, typename Enable = void> 
      struct is_entity;
    template<typename PortCategory, typename Tag = default_tag> 
      struct port_traits;
    template<typename PortTraits, typename Enable = detail::enable_guard> 
      struct is_port_traits;
  }
}