  I illustrate a simple hamiltonian formulation of general relativity, derived
from the work of Esposito, Gionti and Stornaiolo, which is manifestly 4d
generally covariant and is defined over a finite dimensional space. The
spacetime coordinates drop out of the formalism, reflecting the fact that they
are not related to observability. The formulation can be interpreted in terms
of Toller's reference system transformations, and provides a physical
interpretation for the spinnetwork to spinnetwork transition amplitudes
computable in principle in loop quantum gravity and in the spin foam models.
