The constraint operators belonging to a generally covariant system are found
out within the framework of the BRST formalism. The result embraces quadratic
Hamiltonian constraints whose potential can be factorized as a never null
function times a gauge invariant function. The building of the inner product
between physical states is analyzed for systems featuring either intrinsic or
extrinsic time.Comment: 4 pages. Talk given at the Third Conference on "Constrained Dynamics
and Quantum Gravity" held in Sardinia (Italy), September 1999. Journal
reference:Nucl. Phys. B (Proc. Suppl.) 88 (2000) 322-32