  This is a review of the existing ideas in modelling the transition from the
photoproduction ($Q^2 = 0$) to the deep inelastic scattering region. The
available data of the proton structure function are analyzed from the point of
view of the total $\gamma^* p$ cross section behavior with $W$ and the results
are compared to different parameterizations. The question whether DIS processes
are hard or soft is discussed.
