No where in section 5 do we define what a '278i' is.

278i is used in the diagram at 5.2 (and seems to be clear what it is)
In 5.2.6 Prior Authorization Inquiry - we don't 'mention' a 278i
but in 5.2.7.1 we state, " The intermediary SHOULD execute a 278i to return the status."

Suggest in 5.2.6 (last paragraph) we add (278i Request) and (278i Response):
The information in the Bundle is mapped to a 278 Health Care Services Review Information - Inquiry transaction (278i Request). The 278 Health Care Services Review Information - Response (278i Response) is then mapped to a PAS Inquiry Response Bundle with the results of the inquiry contained in the Bundle.