Which database tool is suitable for a particular project, what needs to
be done to allow for new queries, and so on -- those are engineering
problems whose solutions may be affected somewhat by the developer's
preferences and prejudices after the requirements of the project are
taken into account.

The ZODB vs. RDBMS debate is interesting as a vehicle for educating
everyone about the relative strengths and weaknesses of the two kinds
of tools, so without taking any theological position one way or the
other, I will just pitch in the following consideration:

In a standalone application (e.g. a self-contained web site), you can
pretty much do whatever works, and ZODB is certainly attractive as an
option for many Python-based systems. In most applications that involve
valuable data, it is a bottom-line requirement that other applications
have access to the data. That is basically why databases were invented
in the first place. In any environment where those other applications
are not developed or controlled by Python programmers, it is going to
be difficult to use ZODB as the main data storage, no matter how nice
it might be.

Jim Dukarm
DELTA-X RESEARCH