  A number of large spectroscopic surveys of stars in the Milky Way are under
way or are being planned. In this context it is important to discuss the extent
to which elemental abundances can be used as discriminators between different
(known and unknown) stellar populations in the Milky Way. We aim to establish
the requirements in terms of precision in elemental abundances, as derived from
spectroscopic surveys of the Milky Way's stellar populations, in order to
detect interesting substructures in elemental abundance space. We present a
simple relation between the minimum number of stars needed to detect a given
substructure and the precision of the measurements. The results are in
agreement with recent small- and large-scale studies, with high and low
precision, respectively. Large-number statistics cannot fully compensate for
low precision in the abundance measurements and each survey should carefully
evaluate what the main science drivers are for the survey and ensure that the
chosen observational strategy will result in the precision necessary to answer
the questions posed.
