Since the beginning of the ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) project, it has been recognized that the expected challenging scientific results can be achieved only if an integrated view of the end-to-end operations is properly tackled. Hunting for rocky exoplanets and/or studying the possible variations of physical constants requires not only a dedicated, state-of-the-art spectrograph in terms of hardware and optics, but also a tailored observation strategy, data reduction pipeline and data analysis tools (ESPRESSO will be the first ESO instrument for which a customized Data Analysis Software will be provided to the community by the Consortium). In this paper we present the planned data flow system (DFS) for ESPRESSO as emerged after the Preliminary Design Review held in November 2011. Main requirements in terms of observation strategy/preparation and data reduction/analysis are analyzed and the corresponding foreseen (conceptual) design, able to fulfill them, discussed. Eventually, peculiarities and challenges needed to adapt ESPRESSO DFS in the pre-existing ESO/VLT DFS framework are outlined.