  We show that the previously introduced CKMT model, based on conventional
Regge theory, gives a good description of the HERA data on the structure
function F_2^D for large rapidity gap (diffractive) events. These data allow,
not only to determine the valence and sea quark content of the Pomeron, but
also, through their Q^2 dependence, give information on its gluonic content.
Using DGLAP evolution, we find that the gluon distribution in the Pomeron is
very hard and the gluons carry more momentum than the quarks. This indicates
that the Pomeron, unlike ordinary hadrons, is a mostly gluonic object. With our
definition of the Pomeron flux factor the total momentum carried by quarks and
gluons turns out to be 0.3-0.4 - strongly violating the momentum sum rule.
