> After working with the system experts to build this control structure, we immediately noticed missing feedback from controller C to controller B–in other word

> After working with the system experts to build this control structure, we immediately noticed missing feedback from controller C to controller B–in other words, controller B did not have enough information to support the decisions it needed to make There is a feedback loop through D? And why does the same issue not apply to the missing directed edge from B to D? EDIT: I figured it out on a reread, the vertical up/down orientation matters for whether an edge represents control vs feedback, so B is merely not controlling D, which is fine. But if B is only controlling C as a way to get through to D (which is what I would have guessed, absent other information), what's the issue with that?