  We consider conditions that allow us to find an optimal strategy for
sequential decisions from a given data situation. For the case where all
interventions are unconditional (atomic), identifiability has been discussed by
Pearl & Robins (1995). We argue here that an optimal strategy must be
conditional, i.e. take the information available at each decision point into
account. We show that the identification of an optimal sequential decision
strategy is more restrictive, in the sense that conditional interventions might
not always be identified when atomic interventions are. We further demonstrate
that a simple graphical criterion for the identifiability of an optimal
strategy can be given.
