“…There has been much work on how to efficiently express the joint distribution of multidimensional data [24, 26, 28, 32-34, 36, 38, 39, 41-43, 48, 50, 61, 65, 66, 72, 74, 81, 94, 95, 97]. There is also some work on histograms for special types of data, such as XML [12,18,98,100], spatial data [47, 55-57, 64, 68, 75, 90, 92, 93, 99, 102, 103], graph [29], string [44][45][46]71]; or for privacy [37,60,62].…”