anchor.diff:  
   -define(SERVER, ?MODULE).
   
  --record(state, {}).
  +-record(state, {
  +          nodes = [{node(), alive}] :: [{node(), term()}]
  +         }).
   
   %% TODO: specifies the proprietary schedule time format.
   -type schedule() :: term().
  +-type detail() :: binary().
   
   %%%===================================================================
   %%% API
  
positive.code:          cancel_task/1,
           show_schedule/1,
           show_schedules/0,
           members/0
          ]).
  
  %% gen_server callbacks
  
negative.code: %%                                  {stop, Reason, State}
  %% @end
  %%--------------------------------------------------------------------
  handle_cast({leave, Node}, State) ->
      NewNodes = [{Node, leaving}|State#state.nodes],
      % TODO: health checks, if 'Node' is healthy, node status changes 
      %       alive.
      {noreply, NewNodes};
  handle_cast({join, Node}, State) ->
      NewNodes = [{Node, joinning}|State#state.nodes],
      % TODO: health checks, if 'Node' is healthy, node status changes 
      %       alive.
      {noreply, NewNodes};
  handle_cast(_Msg, State) ->
      {noreply, State}.
  
  %%--------------------------------------------------------------------
  %% @private
  