Going from the astronomer submitting an observing proposal to the
reception of the data of the corresponding observations requires quite
a number of steps: TAC/OPC selection, phase II, scheduling, observations, quality control, data pre-reduction and data delivery. In this contribution, the architecture of ESO's data flow and in particular the evolution of the concept, role an even definition of the archive is presented. Coming from the tail end of the ESO data flow, the archive is now the central repository of information about observations and plays initially mostly a technical, operational role.