Question on Addresses and Not Null constraints

["Chris Travers" <..hidden..>]

One thing that is remarkably hard to model relationally is address
data.  In particular different places have different semantics.  Some
countries have mail codes while some do not.  Some places it makes
sense to track states and provinces while in some countries this
doesn't make sense.  And this is not even trying to track things like
street addresses in cities like Managua....

So, I am wondering if we should track some additional data in the
application.  For example, we could track which countries should
require states data, or we could simply keep with a minimal of
not-null constraints.

What do people think?

Best Wishes,
Chris Travers