Before revision:  However, finding such subsets of minimum cardinality is NP-hard, and most research has focused on practical heuristics without performance guarantees. Additionally, the use of exact nearest-neighbors is always assumed, ignoring the effect of condensation in the classification accuracy when nearest-neighbors are computed approximately. In this paper, we address these shortcomings by proposing new approximation-sensitive criteria for the nearest-neighbor condensationproblem, along with practical algorithms with provable performance guarantees.
After revision:  However, the guarantees of a coreset hold for any query point, and not only for the points of the nearest-neighbor condensationproblem, along with practical algorithms with provable performance guarantees.