The extraction of neutrino oscillation parameters often requires the
unambiguous identification of the reaction mechanism to be used for the energy
determination. The use of nuclear targets and of beams with broad energy
distributions complicates this task because it requires the reliable
description of many different elementary processes and the use of event
generators to isolate and identify them. In this talk I briefly summarize our
present understanding of this task.Comment: Contribution to PANIC11, July 24-29, 2011, Cambridge, US