Column descriptions - could they be propagated to new tables?

Since I discovered the facilities in Postgres for providing and listing
column descrptions, I have found them very useful, especially for adding a
string showing physical units to my columns.  For example:

\d+ cat
                       Table "public.cat"
      Column      |       Type       | Modifiers | Description
-----------------+------------------+-----------+--------------
  src_num         | integer          |           |
  ra              | double precision |           | deg
  decl            | double precision |           | deg
  radec_err       | real             |           | arcsec
  lii             | double precision |           | deg
  bii             | double precision |           | deg
  pn_cts          | real             |           | counts

However if one performs a JOIN creating a new table, all these
descriptions fail to transfer.  I haven't been able to find any easy way
of propagating the descriptions - would it be a useful facility to have
them propagated automatically?  I would have thought that things like
units would be useful even in many scientific applications, e.g. to have
monetary columns described as dollars/pounds/euros or whatever.


--
Clive Page
Dept of Physics & Astronomy,
University of Leicester,
Leicester, LE1 7RH,  U.K.