Well, Roy has a way of describing things from a Systems Engineering perspective. that can confuse when read from people with a different context. I think where

Well, Roy has a way of describing things from a Systems Engineering perspective. that can confuse when read from people with a different context. I think where HTTP digest etc. comes in is the 'successful mapping' bit. While the abstract API should not specify HTTP digest, the materialised API that people actually use (the mapping of the API onto HTTP) should.