“…Most existing research using this approach has focused on calculating statistical functions or measurements with a given ε error, using a poly-logarithmic memory amount in the size of the stream and the domain of the incoming data. These functions estimate, for example, the number of distinct data present in a given stream [9], [23], [29], the frequency moments [2], the most frequent elements [2], [19], [40], [37], the entropy of a flow [17], [34], the co-variance between several streams [3] or the relative entropy between a biased stream and a uniform stream [7], [4].…”