  A real photon has a complicated nature, whereby it may remain unresolved or
fluctuate into a vector meson or a perturbative q-qbar pair. In gamma-gamma
events, this gives three by three combinations of the nature of the two
incoming photons, and thus six distinct event classes. The properties of these
classes are partly constrained by the choices already made in our related
gamma-p model. It is therefore possible to predict the energy-dependence of the
cross section for each of the six components separately. The total cross
section gives support to the idea that a simple factorized ansatz with a
pomeron and a reggeon term can be a good approximation. Event properties
undergo a stepwise evolution from p-p to gamma-p to gamma-gamma events, with
larger charged multiplicity, more transverse energy flow and a higher jet rate
in the latter process.
