That is a tough choice because all of those are very important to DDP! If I had to choose one it would be scope management plan; the reason behind that is that having a general scope of how I am going to execute my DDP it will make it a lot easier for me. Everyone is making some valid points! If there were four other major components that could be the main topics what would you they be? Or could it be more than just four? I think no matter what the development of a device is a team work effect and there are several different responsibilities/duties that have to be done.