  The algebraic classification of the Weyl tensor in arbitrary dimension n is
recovered by means of the principal directions of its "superenergy" tensor.
This point of view can be helpful in order to compute the Weyl aligned null
directions explicitly, and permits to obtain the algebraic type of the Weyl
tensor by computing the principal eigenvalue of rank-2 symmetric future
tensors. The algebraic types compatible with states of intrinsic gravitational
radiation can then be explored. The underlying ideas are general, so that a
classification of arbitrary tensors in general dimension can be achieved.
