  We propose a lattice model to study the dynamics of a driven interface in a
medium with random pinning forces. For driving forces F smaller than a
threshold force F_c the whole interface gets pinned. The depinning transition
can be characterized by a set of critical exponents: the static and dynamical
roughness exponent, the velocity exponent defined by the scaling of the
velocity of the interface with F-F_c, and a correlation length exponent. The
critical exponents are determined numerically in 1+1 and 2+1 dimensions. Our
findings are compared with recent numerical and analytical results for a
Langevin equation with quenched noise, which is expected to be in the same
universality class. Our results support a recent functional renormalization
group calculation by T.Nattermann et.al. (J.Phys.II France 2, 1483 (1992)).
