Before revision:  Given a stream of n items from a data universe U equipped with a total order, the task is to compute a sketch (data structure) of size \mathrm{poly (\log(n), 1/\varepsilon).
After revision:  Given a stream of n items from a data universe U equipped with a total order, the task is to compute a sketch (data structure) of size poly (\log(n), 1/\varepsilon).