  A functional approach for the study of the random walks in random sceneries
(RWRS) is proposed. Under fairly general assumptions on the random walk and on
the random scenery, functional limit theorems are proved. The method allows to
study separately the convergence of the walk and of the scenery: on the one
hand, a general criterion for the convergence of the local time of the walk is
provided, on the other hand, the convergence of the random measures associated
with the scenery is studied. This functional approach is robust enough to
recover many of the known results on RWRS as well as new ones, including the
case of many walkers evolving in the same scenery.
