Okay, so I am scraping the FAA site and keeping track of some airplanes.

A lot of the time I get a tail number and I have it already, so I am
going to store the important information in a file that is
{tailnumber}.xml

That way I can add some of my own information (email address of owner,
airport last sighted).

I've never written any xml. But apparently there are gems I could add
to my Ruby installation which would let me write it.

Suggestions for where to start?

I assume I'll wind up with a file that has
<model>DA20</model>
<serial>408.21</serial>

and I can say things like
  serial = xml('serial')
and
  xml(serial) = '408.21'
right?

I can picture writing these things, but I bet someone has already done the work.

Thanks,
--Colin