  In this article, a new nonparametric and robust method of forecasting
hierarchical functional time series is presented. The method is compared with
Hyndman and Shang's method with respect to their unbiasedness, effectiveness,
robustness, and computational complexity. Taking into account results of the
analytical, simulation and empirical studies, we come to the conclusion that
our proposal is superior over the proposal of Hyndman and Shang with respect to
some statistical criteria and especially with respect to robustness and
computational complexity. An empirical usefulness of our method is presented on
example of management of a certain web portal divided into four subservices. An
extensive simulation study involving hierarchical systems consisted of FAR(1)
processes and Wiener processes has been conducted as well.
