  General formalism for a two-component description of the inelastic
lepton-nucleon scattering in the diffractive region is proposed.
Nonperturbative contribution to electromagnetic structure functions of a
nucleon is described by the modified generalized vector dominance model
containing special cut-off factors restricting the phase volume of initial
qq-pairs of virtual photon's fluctuations. Perturbative QCD contribution is
described by the phenomenological model suggested (in nonunitarized form) by
Forshaw, Kerley and Shaw.
  Formulae needed for a numerical calculation of photonuclear cross sections
integrated over Q^2 are presented. It is argued that in a case of the
photonuclear cross sections at superhigh energies of leptons (E>=10^6GeV),
integrated over Q^2, the following two-component scheme is good enough: the
nonperturbative contribution is approximated by the old parameterization of
Bezrukov and Bugaev, and perturbative one is described by the model of Forshaw,
Kerley and Shaw with parameters determined from DESY data. Corresponding
results of numerical calculations of the perturbative part, for the cases of
muon and tau-lepton scattering at superhigh energies, are given.
