  We analyze three classical field theories based on the wave equation: scalar
field, electrodynamics and linearized gravity. We derive certain generating
formula on a hyperboloid and on a null surface for them. The linearized
Einstein equations are analyzed around null infinity. It is shown how the
dynamics can be reduced to gauge invariant quanitities in a quasi-local way.
The quasi-local gauge-invariant ``density'' of the hamiltonian is derived on
the hyperboloid and on the future null infinity. The result gives a new
interpretation of the Bondi mass loss formula. We show also how to define
angular momentum. Starting from affine approach for Einstein equations we
obtain variational formulae for Bondi-Sachs type metrics related with energy
and angular momentum generators. The original van der Burg asymptotic hierarchy
is revisited and the relations between linearized and asymptotic nonlinear
situations are established. We discuss also supertranslations, Newman-Penrose
charges and Janis solutions.
