  Using many-body theory we develop a set of formally exact kinetic equations
for inhomogeneous condensate and one-body observables. The method is illutrated
for phi^4 field theory in 1+1 dimensions. These equations, when computed with
the help of time-dependent projection technique, lead to a systematic
mean-field expansion. The lowest and the higher order terms correspond to,
respectively, the gaussian approximation and the dynamical correlation effect.
