When talking across applications like that, you might be better off putting
your core functionality in its own app, then having all of your other apps
make XML-RPC or JSON-RPC calls to it. This gives you a good level separation
and means that you can break up your apps and run each of them on a
different server if you want (multi-tier). I have had to do this in the past
and I chose JSON-RPC. It work very well and even passes exceptions across
the wire in the form of a dict. The only thing to keep in mind is that it
can only handle numbers, strings, and booleans. While this may be a turn off
at first, especially if you want to use dates, it's actually pretty trivial
to have those dates be converted to epoch numbers or full date time strings
and back.
