anchor.diff:  
   -type state() :: Table::tid() | atom().
   -type message() ::
  -    {proc_report, Process::atom(), Key::key(), OldValue::rrd:rrd(), Value::rrd:rrd()} |
  +    {report_rrd, Process::atom(), Key::key(), OldValue::rrd:rrd(), Value::rrd:rrd()} |
  +    {report_single, Process::atom(), Key::key(),
  +     NewValue_or_UpdateFun::term() | fun((Old::Value | undefined) -> New::Value)} |
       {web_debug_info, Requestor::comm:erl_local_pid()}.
   
   %% @doc Converts the given Key to avoid conflicts in erlang:put/get.
  
positive.code: -include("scalaris.hrl").
  
  -export([start_link/1, init/1, on/2, check_config/0]).
  -export([proc_set_value/3, proc_get_value/2, proc_exists_value/2]).
  
  -type key() :: string().
  -type internal_key() :: {'$monitor$', Key::string()}.
  
negative.code:     % note: it may happen that the new value created a new slot which already
      % discarded all logged data from the previous (unreported) time slot
      % -> send OldValue, too
      comm:send_local(MyMonitor, {report_rrd, Process, Key, OldValue, Value}).
  
  %% @doc Message handler when the rm_loop module is fully initialized.
  -spec on(message(), state()) -> state().
  on({report_rrd, Process, Key, OldValue, _NewValue}, Table) ->
      % note: reporting is always done when a new time slot is created
      % -> use the values from the old value
      TableIndex = {Process, Key},
      MyData = case ets:lookup(Table, TableIndex) of
                   [{TableIndex, X}] -> X;
                   []      ->
  