Modified Pruning for Query Plan Computation Sample Clauses

Modified Pruning for Query Plan Computation. To be able to prune uncertain rectangular areas (i.e. grid cells or MBRs) against an uncertain query, we cannot utilize the uncertain pruning methods described in Section 4.3, therefore, we adopt a solution based on half-plane pruning method pro- posed in [18]. Figure 4.11 shows the computation of pruned area when both query and points are uncertain. Two uncertain rectangles represent the uncertain query Qu and an uncertain candidate cnd. In contrast to the uncertain half-plane pruning method described in Section 4.3, we cannot define the boundary of pruned area by merely intersecting the four bisectors, because we may miss some points as answers [18]. To compute the pruned area, we find a point o in which Mindist(o, Qu) ≥ Dist(o, cnd), and pass all of the bisectors between the query and the candidate rectangles through this point; The intersection area of all these bisectors is defined as the pruned area. Figure 4.12: Modified verification for query plan