  Let X and Y be separable metrizable spaces, and f:X-->Y be a function. We
want to recover f from its values on a small set via a simple algorithm. We
show that this is possible if f is Baire class one, and in fact we get a
characterization. This leads us to the study of sets of Baire class one
functions and to a characterization of the separability of the dual space of an
arbitrary Banach space.
