Just following on from another thread, I would like us to discuss this subject.
Another forum member mentioned that the Kosa Dachi resembles juji-gatame or a sangaku-jime, and as a general principle I absolutly agree.
However the classical kata do not assume the on your back position and then show the technique, so I do not feel that 'true' ground work is contained within classical karate kata personally. If you look at Kusanku, Chinto, Gojushiho, Pinan Godan there are clear examples of going to one knee for sure (in our Kusanku we do drop down chest to floor as well), but never going to ground on your back?
True groundwork IMO relys on a different root and plane of force (ie the ground on your back, side or front) to Kosa Dachi standing position - outside of general principle's, commonalities this makes a BIG difference in technique execution.
I know we have discussed this and similair topics before but lets look at it again as a group, be interesting to see peoples view and experience.