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.
Categories: hep-ex