Read-write views exist now: you just have to write ON INSERT,
ON UPDATE, ON DELETE rules that show what you think should happen.
Some people seem to think that the system should try to intuit
those rules for them, but I don't believe that's either possible
or desirable. The entire point of a view is that it's not an
exact image of the underlying data, so how is a machine going to
figure out what you want an update on the view to do?
regards, tom lane