“…Thus, as shown in lines 2-12 of Figure 12 we compute two aggregation functions grouping on mach, tstart, and t end . The example instance of table active contains two tuples belonging to the same group which also have the same period: (M1,10,1,5) and (M1, 20,1,5). Based on these two tuples we compute the pre-aggregated result (M1, 30,1,5).…”