We discuss the current status of a computational approach which allows to
evaluate the dielectric matrix, and hence electronic excitations like optical
properties, including local field and excitonic effects. We introduce a recent
numerical development which greatly reduces the use of memory in such type of
calculations, and hence eliminates one of the bottlenecks for the application
to complex systems. We present recent applications of the method, focusing our
interest on insulating oxides.Comment: 11 pages, 5 figures, 1999 MRS Proceedin