Interpolating between Soft and Hard Dynamics in Deep Inelastic Scattering

An explicit model for the proton structure function interpolating between low- (VMD and Regge behavior)and high-$Q^2$ (GLAP evolution) is suggested. The model is fitted to the experimental data in a wide range of the kinematical variables with emphasis on the low-$x$ HERA data. The boundaries, transition region and interface between various regimes are quantified.