  We propose a novel and natural architecture for decentralized control that is
applicable whenever the underlying system has the structure of a partially
ordered set (poset). This controller architecture is based on the concept of
Moebius inversion for posets, and enjoys simple and appealing separation
properties, since the closed-loop dynamics can be analyzed in terms of
decoupled subsystems. The controller structure provides rich and interesting
connections between concepts from order theory such as Moebius inversion and
control-theoretic concepts such as state prediction, correction, and
separability. In addition, using our earlier results on H_2-optimal
decentralized control for arbitrary posets, we prove that the H_2-optimal
controller in fact possesses the proposed structure, thereby establishing the
optimality of the new controller architecture.
