anchor.diff:  
   %% User privileges with regards to handle service.
   -type handle_service_privilege() :: register_handle_service |
  -list_handle_services | delete_handle_service | modify_handle_service |
  -view_handle_service.
  +delete_handle_service | modify_handle_service | view_handle_service |
  +register_handle.
   
   %% User privileges with regards to handle.
  --type handle_privilege() :: register_handle | list_handles | delete_handle |
  -modify_handle | view_handle.
  +-type handle_privilege() :: delete_handle | modify_handle |
  +view_handle.
   
   %%%===================================================================
   %%% API
  
positive.code:     ordsets:union(
          handle_user(),
          ordsets:from_list([
              register_handle,
              list_handles,
              delete_handle,
              modify_handle,
  
negative.code: %%--------------------------------------------------------------------
  -spec handle_service_user() -> [handle_service_privilege()].
  handle_service_user() ->
      [view_handle_service, register_handle].
  
  %%--------------------------------------------------------------------
  %% @doc A privilege level of a handle_service administrator. This level contains all
  