“…The former, histogrambased techniques [18,21,38,37,23,22,36,11,16,14,40,12], summarize the data by dividing it into consecutive intervals, or buckets; typically, a bucket is assigned a single representative value that approximates the data therein; variations to this theme aim to optimize the data representation within a bucket [30,4,42]. The latter methods utilize a predefined hierarchical tree structure such as that defined by the Haar wavelet decomposition [32,41,5,8,9,25,35,12,13] or alternatives that follow a similar pattern [39,26,24].…”