  The Loewner framework for model order reduction is applied to the class of
infinite-dimension systems. The transfer function of such systems is irrational
(as opposed to linear systems, whose transfer function is rational) and can be
expressed as an infinite series of rational functions. The main advantage of
the method is the fact that reduced orders models are constructed using only
input-output measurements. The procedure can be directly applied to the
original transfer function or to the one obtained from the finite element
discretization of the PDE. Significantly better results are obtained when using
it directly, as it is presented in the experiments section.
