Where is the official definition of these terms? I have looked in several Army Regulations and have not found them yet.
I do not know of a single location to find the definitions. That being said, I would recommend AR 700-18 and DA PAM 700-27. I understand you are doing CM work. There should be a Provisioner, a Maintenance Engineer and a Logistics Manager all assigned to the End Item that the COEI relates to. If you have these types of Professionals at your Command it is worth finding one and talking to them. They will have had to have done the Basis of Issue Plan Feeder Data prior to the End Item being put into the Field. They should be able to sit with you and explain the definitions and how they are derived for a system. As well, you will have a better appreciation by reading the AR 700-18 applicable sections. There is also a guide out there on how to do BOIPFD (it may also help).
Tim (Professor Galvin - firstname.lastname@example.org