Before revision: We first pose the Unsupervised Progressive Learning (UPL) problem: learning salient representations from a non-stationary stream of unlabeled data in which the number of object classes increases with time .
After revision: We first pose the Unsupervised Progressive Learning (UPL) problem: learning salient representations from a non-stationary and unlabeled data stream, and identifies a growing number of features that persist over time even though the data is not stored or replayed .