>> - flash back queries
>
> Why do I need NBAK here? I always thought that this can be achieved by
> providing a "flash back depth" parameter to garbage collector to prevent
> garbage-collecting those records and providing the "flash back"
> parameter with the query.

Agree, nbak seems not best candidate for it. talking about delayed GC
we need first to record timestamps of every transaction end to be able set
point in time on which we want to see database state. Also i'm not sure
delayed GC is enough - we need to keep dropped objects too.

>> - database "branches" - database with various independent delta files -
>> very useful for group of people developing/testing on one copy of big
>> production database without interfering with others
>
> I like it :) We have to take care, since people might begin to ask for a
> "MERGE BRANCH <name> INTO HEAD" functionality - might be not very
> trivial to implement.

I think we can live without merging or with requirement that merge of
some branch will invalidate other branches. As it is not possible to merge
more then one branch together.

Regards,
Vlad