"The past perfect system operates in narrative to create a 'flashback' frame. However, in many contexts (e.g., temporal clauses with after or before ), it is optional because the conjunction provides the temporal ordering. The choice to use or omit the past perfect is a decision to foreground or background the sequence of events."
Modality is the system of possibility, necessity, permission, and obligation. Traditional textbooks treat can, could, may, might, must, should as a vocabulary list. Systemic grammar treats them as a gradient scale of commitment. "The past perfect system operates in narrative to