Let X and Y be separable metrizable spaces, and f:X --> Y be a map. We want to recover f from its values on a small set via a simple algorithm. We give sufficient conditions on X to insure this when f is Baire class one. We study the limits of these results. 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.