  In the semiclassical approach, inclusive and diffractive quark and gluon
distributions are expressed in terms of correlation functions of Wilson loops.
Each Wilson loop integrates the colour field strength in the area between the
trajectories of two fast partons penetrating the proton. We introduce a
specific model for averaging over the relevant colour field configurations.
Within this model, all parton distributions at some low scale Q_0^2 are given
in terms of three parameters. Inclusive and diffractive structure functions at
higher values of Q^2 are determined in a leading-order QCD analysis. In both
cases, the evolution is driven by a large gluon distribution. A satisfactory
description of the structure functions F_2(x,Q^2) and F_2^D(3)(xi,beta,Q^2) is
obtained. The observed rise of F_2^D(3) with xi is parametrized by a
non-perturbative logarithmic energy dependence, compatible with unitarity. In
our analysis, the observed rise of F_2 at small x is largely due to the same
effect.
