Before revision:  It is assumed that the proper rational  matrix-valued function is expressed in the transfer function form H(s) = C (sI - A)^{-1} B, where the middle factor is large, whereas the number of rows of C and the number of columns of B are equal and small.
After revision:  It is assumed that the proper rational part of the rational matrix-valued function is expressed in the transfer function form H(s) = C (sI - A)^{-1} B, where the middle factor is large, whereas the number of rows of C and the number of columns of B are equal and small.