The basic idea is that with database journaling you can extract a snapshot of the data at any past date. At the time of the talk, the speaker said he was going to make the code public. I don't know if this was ever done.
George Essig
> I've been asked by a colleague about methods to keep track of > 'previous' contents of a table - i.e. changes made and a way of > getting back to a previous state.