Hi Rui,
thanks for your reply.
Unfortunately i could not find "how to implement savedraft" on wiki.scn.sap.com. If you mean another wiki page, i think i have no access to this.
As Tilmann mentioned in the post below, SAP is currently working on a more detailed documentation about this topic.
Hopefully it takes not to long until this document will be released.
https://scn.sap.com/message/16553589#16553589
Best regards
Simon