Interested in a spec for starting desktop sessions via gdm2

[Brian Cameron <Brian Cameron Sun COM>]

I have recently become the maintainer of GDM2 and a feature I would like to
work on is to support the ability to login to a specific desktop session
(such as one defined via gnome-session-save) from the login screen.  I
think the best approach would be if GNOME and KDE could specify the available
sessions via a common format and in a file with a common name.

I'm not well versed with KDE session setup so I am wondering if there might
be someone who would be able to help put together a reasonable specification.
Then I'd be happy to implement it so it works in GDM2.

Brian