Subspace global skyline query processing

Abstract

Global skyline, as an important variant of skyline, has been widely applied in multiple criteria decision making, business planning and data mining, while there are no previous studies on the global skyline query in the subspace. Hence in this paper we propose subspace global skyline (SGS) query, which is concerned about global skyline in ad hoc subspace. Firstly, we propose an appropriate index structure RB-tree to rapidly find the initial scan positions of query. Secondly, by making analysis of basic properties of SGS, we propose a single SGS algorithm based on RB-tree (SSRB) to compute SGS points. Then an optimized single SGS algorithm based on RB-tree (OSSRB) is proposed, which can reduce the scan space and improve the computation efficiency in contrast to SSRB. Next, by sharing the scan space of different queries, a multiple SGS algorithm based on RB-tree (MSRB) is proposed to compute multiple SGS (MSGS). Finally, the performances of our proposed algorithms are verified through a large number of simulation experiments.

The subspace global skyline query processing over dynamic databases

“…We calculate the dimensionality similarities of two queries in all their shared dimensions through (2). For other dimensions which cannot be shared, the dimension similarities are 0.…”

“…q 2 0.7, , 0.8 represents the best candidate materials for u 2 . They are m 2 , m 4 , m 5 In our early work [2], we have studied the global skyline problem in ad hoc subspaces in the static databases and proposed global skyline query algorithms SSRB, OSSRB and MSRB. However, the information of databases may change as time passes.…”

“…In [2], we have proposed two indexes, RB-tree and histograms to process the subspace global skyline queries. In this paper, we propose the maintenance approaches of RBtrees and histograms.…”

“…2. In [2], we have proposed algorithms SSRB and OSSRB to process the single subspace global skyline query. In this paper, by retaining reasonable structures, the subspace global skyline can be quickly updated without recalculation.…”

“…3. In [2], we have proposed algorithm MSRB to process multiple subspace global skyline queries. In this paper, we extend MSRB, so that it can be used in dynamic databases.…”