[mythtv] How are backend/frontend/modules separated?

[Thor Johnson]

Ok... a dev question that will probably prompt me to 
rewrite a few things (such as changing descriptions 
of recorded programs):

What resources are which programs supposed to access?
(e.g.  should mythfrontend *not touch* the database)

It seems almost logical to have that restriction
(that way, you don't need to have the mysql net
permissions installed unless you're running mythweb),
but it requires implementing messages to do things
that touch the database (e.g. my edit patch boils
down to an update statement that is buried in
the container for recorded programs used in 
playbackbox.  If mythfrontend shouldn't touch
the database, I'll need to add appropriate
messages...).

TIA,
Thor Johnson