Can Semiclassical garvity gives exact or approximate results ?

zetafunction

if we use Semiclassical Quantum Gravity , will we get or can we get EXACT results ? or only asymptotic approximation

can we use the 'old quantum rule' in Semiclassical gravity ?? i mean the fact that for the conjugate moment to the metric g we have

[tex] \oint \Pi _{a,b}dg_{a,b} =n.h [/tex]