anchor.diff:  %% handle_call
   %% ------------------------------------------------------------------
   
  +%% @hidden
   handle_call({authentication, Username, Password}, undefined) ->
   	% TODO mnesia backed
   	{reply, undefined, undefined};
  
positive.code: %% terminate
  %% ------------------------------------------------------------------
  
  terminate(Why, State) ->
  	?info("Going down:  ~p", [Why]),
  	#state{callback = Callback, substate = Substate} = State,
  
negative.code: %% code_change
  %% ------------------------------------------------------------------
  
  %% @hidden
  code_change(_Oldvsn, State, _Extra) ->
  	{ok, State}.
  
  