Question re: TODO Item 'separate SERIAL type'

In the TODO, in the Type section, someone has proposed as 'separate SERIAL
type', which I assume is a type distinct from the SERIAL mapping to int
nextval... that exists now.

Can anyone elaborate on why this would be useful? I'm curious.

I've tried searching the lists, but I find too many references to common
questions about the current SERIAL pseudotype to come up with much.

Thanks!
-- 
Joel Burton   <jburton@scw.org>
Director of Information Systems, Support Center of Washington