I have just had a quick look at the URL in identifier problem. I don't
think there is any existing metadata that is suitable to be mapped, so
the solution will have to involve source code modification of oaiserver.

I have added a ticket to trac, which contains a few more details of the
problem:
http://trac.greenstone.org/ticket/654

Hopefully I will be able to work on this early next year.

Regards,
Katherine