  The diffractive dissociation of virtual photons, gamma*p -> Xp, has been
studied with the H1 and ZEUS detectors at HERA using various complementary
techniques. Events have been selected by direct tagging of the outgoing proton
or by requiring a large rapidity gap between the proton and the system X. The
diffractive contribution has also been unfolded by decomposition of the
inclusive hadronic final state invariant mass distribution. Here, detailed
comparisons are made between diffractive cross section measurements obtained
from the different methods and the two experiments, showing them to be
consistent within the large uncertainties associated with the treatment of
proton dissociation processes. First steps are taken towards the combination of
the H1 and ZEUS results.
