Multi-subspace Skyline query computation method

A computing method and subspace technology, applied in computing, special data processing applications, instruments, etc., can solve problems such as low efficiency, achieve the effect of improving efficiency and reducing the number of data comparisons

Inactive Publication Date: 2015-10-28
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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  • Abstract
  • Description
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  • Application Information

AI Technical Summary

Problems solved by technology

Call it the multi-subspace Skyline query problem. Most of the current subspace Skyline algorithms focus on a specific subspace or all subspaces, so they are inefficient when solving any number of subspace Skyline query problems.

Method used

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Embodiment 1

[0036] Embodiment 1 of the present invention has introduced the method for generating subspace cube group (SSG) by a plurality of subspaces, and this structure has guaranteed the effective execution of follow-up algorithm, and specific step process is as follows figure 2 shown, including:

[0037] (1) First detect all subspaces in the database system to form a set of subspaces O={V 1 ,...,V n}, where the number of subspaces included is assumed to be n;

[0038] (2) Initialize the subspace cube group set SSG as an empty set, and then process all subspaces in the subspace set O one by one;

[0039] (3) If all subspaces have been processed, return the current SSG to end the process, otherwise continue;

[0040] (4) If the currently processed subspace V i If it belongs to SSG, then process the next one, otherwise continue;

[0041] (5) put V i The place is constructed as a subspace cube SSC and added to the SSG;

[0042] (6) Return the SSG obtained from the above calculati...

Embodiment 2

[0045] Embodiment two of the present invention is as Figure 4 As shown, the generation method of the subspace candidate set (SSKY) is introduced. SSKY avoids the determination of the dominance relationship of the data points that must be the result of the subspace Skyline, and improves the efficiency. The specific implementation process includes:

[0046] (1) First, for the subspace V being calculated, find all child subspaces of V according to its corresponding subspace cube SSC;

[0047] (2) Find the union of the Skyline result sets of all child subspaces of V, and assign it to SSKY;

[0048] (3) For the Skyline results of each child subspace of V, find out the data points that are not the Skyline results on V, and assign them to TEMP;

[0049] (4) Remove the TEMP of all child subspace Skyline result sets of V from SSKY;

[0050] (5) Finally, the obtained SSKY is the candidate set of subspace V.

Embodiment 3

[0052] Embodiment three of the present invention is as Figure 5 As shown, the specific execution flow of the MSSCA algorithm in the present invention is described. Based on the foregoing description, this embodiment shows a multi-subspace Skyline query algorithm based on subspace cube groups combined with multiple optimization methods——MSSCA algorithm. include:

[0053] Algorithm at first utilizes the subspace cube generation method in the first embodiment, a plurality of subspaces existing in the system are preprocessed, subspace collection O={V 1 ,...,V v} into a subspace cube group; next, the data set is preprocessed, and the data set is sorted on all the dimensions contained in the first layer of the subspace cube group, thereby forming several data sequences; after that, due to the first layer All subspaces are 1-dimensional, so the Skyline results of the first layer of subspaces can be directly obtained according to the corresponding ordered data sequence; after that,...

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Abstract

The invention provides a method for computing multi-subspace Skyline queries and belongs to the orientation of data management and queries in the computer field. According to the method, firstly, in case of co-existence of multiple subspace Skyline queries in a database system, a sub-space cubic group structure is designed, and on the basis of the structure, a computation method capable of simultaneously processing multiple subspace Skyline queries, namely an MSSCA algorithm, is designed; the algorithm is capable of effectively solving the multi-subspace Skyline query problem. In the implementation process of the algorithm, a method of sharing Skyline result sets of child spaces is utilized thoroughly to directly put points that must be Skyline results of a parent space into the result set, and therefore, the times of judgment is reduced; besides, the algorithm is also capable of further reducing the times of dominance relation judgment by use of such methods as maximum value pruning and summating filtering; as a result, the efficiency is effectively improved. The method disclosed by the invention is capable of dealing with co-existence of multiple subspace Skyline queries in the database system and guaranteeing the efficiency of the algorithm by use of a series of sharing and filtering methods; in short, the method has a great practical application value.

Description

technical field [0001] The invention discloses a multi-subspace Skyline query calculation method, in particular to a query calculation method for calculating Skyline queries existing in several subspaces simultaneously in a database system, and belongs to the technical field of data management and query in the computer field . Background technique [0002] In recent years, Skyline calculation and its calculation methods have attracted the attention of many researchers. The main reason is that Skyline query results play a very important role in many applications, such as multi-objective decision-making, data mining and visualization, and user preference query. The initial Skyline query research in the database field mainly focused on the full-space Skyline query, and with the development of high-dimensional and massive data in the database, the maximum Skyline results obtained in the entire space become meaningless. In many scenarios, users are not necessarily interested in...

Claims

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Application Information

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IPC IPC(8): G06F17/30
CPCG06F16/90335
Inventor 秦小麟王潇逸
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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