  A review of theoretical models of diffractive structure functions in deep
inelastic scattering (DIS) is presented with a view to highlighting distinctive
features, that may be distinguished experimentally. In particular, predictions
for the behaviour of the diffractive structure functions $F_2^D, F_L^D,
F_2^{D(\mbox{\small{charm}})}$ are presented. The measurement of these
functions at both small and high values of the variable $\beta$ and their
evolution with $Q^2$ is expected to reveal crucial information concerning the
underlying dynamics.
