[Zope] Where to put business logic?

I know that this issue has been up before, at least partly. Is there an "unwritten" rule on where to put business logic in an Zope app? Example: where to validate data input? In the submit method or somewhere in the underlying database (PostgreSQL, MySQL, Oracle etc.)? What could the underlying motives be for choosing one or the another strategy? In the particular case I'm going to use it for a db case in school and I intend to use Zope to present the data etc. instead of using MS VC++ 6.0 which I don't get the idea of anyway. -- Best regards / Mvh., Steen Suder, sysadm kollegie6400.dk -|- OpenSource --- Sign of the time Scan-Aqua ADVARSEL WARNING http://www.uk.k64.dk/sfs/Scan-Aqua/