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:              end,
      NewData = rrd:add_nonexisting_timeslots(MyData, OldValue),
      ets:insert(Table, {TableIndex, NewData}),
      Table;
  
  on({web_debug_info, Requestor}, Table) ->
  
negative.code: -include("scalaris.hrl").
  
  -export([start_link/1, init/1, on/2, check_config/0]).
  % (temporarily) storing monitoring values in the calling process:
  -export([proc_set_value/3, proc_get_value/2, proc_exists_value/2]).
  % sending monitoring values to the monitor process
  -export([monitor_set_value/3]).
  
  -type key() :: string().
  -type internal_key() :: {'$monitor$', Key::string()}.
  