Access method of xml data query result based on branch tree of multi-level subquery result

A technology for query results and data query, applied in the database field, it can solve problems such as complex data structure, and achieve the effect of ensuring high-performance access

Inactive Publication Date: 2016-01-20
BEIJING UNIV OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Space overhead constraints and cross-reference requirements complicate data structures

Method used

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  • Access method of xml data query result based on branch tree of multi-level subquery result
  • Access method of xml data query result based on branch tree of multi-level subquery result
  • Access method of xml data query result based on branch tree of multi-level subquery result

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Embodiment Construction

[0030] 1. A method for organizing query results of an XML data query; this XML data query is manifested as a multi-branch tree-type multiple cycle calculation composed of nested join operations, Cartesian product operations, and selection operations.

[0031] 2. The query result of XML data query is composed of multi-layer sub-query results, which have a tree structure. Each subquery result is saved in 1 data node. Each data node consists of an XML element and an ordered mapping table, which stores the subquery results obtained in the XML subtree rooted at the current XML element. The entries of the mapping table in the data node are arranged according to the nesting depth, and each entry stores the mapping relationship between one loop variable and one data node sequence. The data node sequence in the mapping entry is arranged according to the document order of the XML data, saving each XML data element bound to the current loop variable and its subquery result.

[0032] 3....

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Abstract

The invention provides an XML data query result visiting method based on multi-level subquery result branch trees, and belongs to the technical field of databases. The method is suitable for a query mode of multi-level branch tree type multiple repeating computation. The method is characterized in that the method is based on binding, a Cartesian product and selection, the multi-level subquery result branch trees are constructed for multiple levels of XML data query results, and each subquery result is organized in a data node composed of an XML element and an ordered mapping table. Table entries which are distributed in the mapping tables stores a mapping relation of loop variables and a data node sequence, and the data node sequence is organized according to serial numbers of the XML elements. During data visiting, starting from a root node, the lower level subquery result corresponding to the loop variable in one level is found in the mapping table. The subquery results corresponding to the loop variables can be obtained after searching level by level. According to the method, query can be carried out according to different sequencing requirements of users and special data organization can be expanded. Meanwhile, visiting, sequencing and expandable requirements of the XML data query results are met.

Description

technical field [0001] The invention relates to the organization, construction and access method of query results of XML data query in an XML data processing system, belongs to the technical field of databases, and is used for efficiently organizing and constructing query results of typical XML data queries and providing flexible data access methods. technical background [0002] Extensible Markup Language (XML) has become the de facto standard for network data exchange and data sharing. XML data query and data processing have become very common functions in Internet network software systems. In view of the semi-structured features of XML data, a typical XML data query is a multi-branch tree-type multi-loop calculation composed of nested join operations, Cartesian product operations, and selection operations, with complex query patterns. The same set of XML data elements in the query result may belong to different subquery results at the same time. Space overhead constrain...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F17/30
Inventor 廖湖声李小青刘畅高红雨苏航
Owner BEIJING UNIV OF TECH
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