Hi Attila, Martin and Paul,
at SAP we are currently experimenting with draft management. In 7.50 SP2 you might find the above mentioned classes. However, this was our first version and is already outdated and therefore not documented. It will be deleted with upcoming versions.
Unfortunately we have to wait a bit more for a native draft support in the ABAP stack...
@Attila: You are totally right. Without draft it is hard to perform backend logic (validations, determinations, field-control), without beeing able to persist (incomplete, inconsistent) data in the backend. Copying active to draft data is definitely a good starting point. Without a native BOPF support or even an E2E support from client to backend this is pretty hard. But unfortunately also a lot of other questions have to be answered (What about locks? What about locks if this data is already used in a non-Fiori world? Who cleans up the drafts (garbage collector)? How to achieve a good performance with regards to "state"?).
Our ideas about Edit() and activate() are, that they are performed on one dataset, but do return a different one. This can be done in BOPF but also on a higher level, as long as this is not integrated.
Last year at TechEd we saw, how a draft app could look like. At TechEd this year we want to give a lab preview on how to build draft apps in the future....
Best regards,
Marcel