  In this paper, we are concerned with the regional boundary controllability of
the Riemann-Liouville time fractional diffusion systems of order $\alpha\in
(0,1]$. The characterizations of strategic actuators are established when the
systems studied are regionally boundary controllable. The determination of
control to achieve regional boundary controllability with minimum energy is
explored. We also show a connection between the regional internal
controllability and regional boundary controllability. Several useful results
for the optimal control from an implementation point of view are presented in
the end.
