We present a definition of generating functions of canonical relations, which
are real functions on symmetric symplectic spaces, discussing some conditions
for the presence of caustics. We show how the actions compose by a neat
geometrical formula and are connected to the hamiltonians via a geometrically
simple variational principle which determines the classical trajectories,
discussing the temporal evolution of such ``extended hamiltonians'' in terms of
Hamilton-Jacobi-type equations. Simplest spaces are treated explicitly.Comment: 28 pages. Edited english translation of first author's PhD thesis
(2000