  The aim of this chapter is to introduce the concept of regional boundary
exponential reduced observability in connection with the sensors
characterizations on a sub-region on boundary of the considered domain
boundary. More precisely, we explore the original results devoted to this
concept in linear dynamical systems which is generated by a strongly continuous
semi-group in Hilbert space of order one. Thus, the existence of sufficient
conditions is presented and examined for regional boundary exponential reduced
estimator in parabolic infinite dimensional systems. Finally, we apply these
results to the exchange systems with various strategic sensors.
