It is worthwhile to summarize now the essential features of the generic GRB model that arose from the previous discussion. Compactness has led us to the requirement of relativistic motion, with a Lorentz factor 100. Ockham's razor and the desire to limit the total energy have lead us to the idea that the observed gamma-rays arise in the process of slowing down of a relativistic energy flow, at a stage that the motion of the emitting particles is still highly relativistic.
This leads us to the generic picture mentioned earlier and to the suggestion that GRBs are composed of a three stage phenomenon: (i) a compact inner hidden "engine" that produces a relativistic energy flow, (ii) the energy transport stage and (iii) the conversion of this energy to the observed prompt radiation. One may add a forth stage (iv) conversion of the remaining energy to radiation in other wavelengths and on a longer time scale - the "afterglow".