DTD documents and Ruby

Has anyone ever run across some tools that would read a DTD and
produce usable Ruby classes from that?

Seems like quite a daunting task, but thought maybe someone has given
it a shot.

I did find the Quickbooks Ruby gem and I'm looking at pieces of that,
but thought I'd post a question to see if there might be more out
there.

Thanks for any ideas.

Mike B.