I've a master-detail-detail, like
Master: MKey1
Detail: Mkey1 + Dkey1
Detail-Detail: Mkey1 + Dkey1 + DDKey1

I've set constraints in Detail so when Mkey1 changes, cascading is done to Detail.
I've also set two constraints to Detail-Detail so when
a) MASTER Mkey1 change, Detail-Detail is updated
b) DETAIL Mkey1+Dkey1 change, Detail-Detail is updated

But when MASTER Mkey1 changes, Detail is updated too, so what will happen to Detail-Detail? Updated twice? Server crash?
Is that a bad design and I'd better drop a) constraints? (it's somehow logically correct, but not practically).
BTW, I've read about past problems in foreign key integrity management by IB 5.6. Is Firebird RC2 ok? Or I'd better rely only upon triggers?
Thanks for your advices
Marco Menardi