We show how a linear control systems theory for the backward nabla
differential operator on an arbitrary time scale can be obtained via Caputo's
duality. More precisely, we consider linear control systems with outputs
defined with respect to the backward jump operator. Kalman criteria of
controllability and observability, as well as realizability conditions, are
proved.Comment: Submitted November 11, 2009; Revised March 28, 2010; Accepted April
03, 2010; for publication in the International Journal of Control
