Just a note on the new History.dat, guys...
Parent-clone relationships in History.dat now follow the rule of oldest-known-in-Japan-if-originally-published-in-Japan as parent set. This differs from MAME.
Aug. 17, 12: ATTN Contributors; the new rule 'PRIORITY TO ORIGINAL VERSIONS' is live. When a game was originally released in Japan, all information goes to the Japanese entry, and the outside-Japan versions are considered as clones and should contain only information about non-Japanese versions
I do not know if previous entries have been converted to this rule.