I noticed that in the freely available TWIC databases (and perhaps in other databases as well) there are sometimes different notations for the same move. Just now I am looking at the Ruy Lopez where in some games white plays 6. Re1 while in others it is Rfe1 (which are of course the same move). Incidentally white scores much better with "Rfe1" ;-) Anyway having different notations for the same move makes reading the statistics (white win / draw/ black win) much harder.
That's why I was wondering how to get rid of such problems in the database. Also what other ways are there to clean up the database (e.g. removing duplicate games, ....)?