anchor.diff:          [{Key, {Value, WriteLock, ReadLock, Version}}] ->
               ?ETS:insert(DB, {Key, {Value, WriteLock, ReadLock - 1, Version}}),
               {DB, ok};
  -        [] ->
  -            {DB, failed}
  +        [] -> {DB, failed}
       end.
   
   %% @doc get the locks and version of a key
  
positive.code:             {DB, ok};
          [{Key, {_Value, false, _ReadLock, _Version}}] ->
              {DB, failed};
          [] ->
              {DB, failed}
      end.
  
  %% @doc sets a read lock on a key
  
negative.code:                             ReadLock == 0 andalso
                              OldVersion < Version of
                              true ->
                                  ?ETS:insert(DB, {Key, {Value, WriteLock,
                                                         ReadLock, Version}}),
                                  DB;
                              false -> DB
                          end
                  end
          end,
  