CSBTT:一种基于二叉树遍历的XML文档编码模式

XML文档数据编码模式是XML文档查询处理的基础, 好的文档编码模式有利于提高文档的查询效率. 为了解决XML数据查询效率低、支持动态更新等问题. 本文在二叉树遍历的编码基础上, 引入二叉树的三叉链表存储结构对XML文档结点进行编码. 该编码利用自然数作为编码序号, 因此编码长度较短; 引入结点双亲指针, 方便结点之间结构关系的判定, 结点采用三叉树链式存储, 方便文档的更新操作.     

XML 动态区间编码方法

提出了适用于XML文档更新环境下的区间编码方法——DCLS(dynamic containment labeling scheme).DCLS将基于整数的编码泛化到基于向量的编码,扩展了传统静态区间编码方法,有效避免了XML文档更新时的重新编码.不论文档更新与否,DCLS都显示了良好的性能:DCLS利用基于整数的静态区间编码方法进行初始编码,在文档不更新的环境下,具有较高的存储效率和查询性能;同时,DCLS将整数视为特殊向量,不仅能够支持文档更新,而且更新效率高;特别是倾斜插入时,DCLS可以避免编码位长的快速增加.实验结果表明,与已有的动态区间编码方法相比,DCLS具有更好的性能.     

IDD:DDE编码改进方法

编码技术是XML查询处理的基础,为适应XML更新需要,近年来提出很多动态编码方法,大致可分为基于位串的编码和基于向量的编码.当XML更新时,动态编码方法应该产生最短位长新编码分配给插入节点.位串编码具有这个性质,而对于向量编码,却是一个难点.以DDE为例,提出了向量编码的最短位长新编码计算方法.该方法将问题建模为整数规划,通过构造所有不可约分数求得最短位长新编码.和原有简单利用向量相加计算新编码相比,优点包括了重用已删编码,降低编码长度,提高查询性能,具有更好查询支持等.     

一种新的支持XML文档更新的编码方法

提出了一种新的支持XML文档更新的编码方法——DVLS(Dynamic Vector Labeling Scheme)。DVLS仅由3个向量组成,克服了传统前缀编码中编码长度随着XML文档树深度的增加而增长的缺陷,其主要思想是:利用向量的加法来支持XML节点数据的更新,并分别针对静态和动态XML文档提出优化方案,以提高查询效率。在向量序的基础上,通过与DDE编码的对比实验,验证了DVLS编码的高效性。     

一种基于二叉树的Native XML数据库文档编码机制

在对于现有编码机制进行综述的前提下,提出一种新的XML文档编码机制,该编码机制基于完全二叉树的结构顺序编码。在该XML文档编码机制下,判断节点之间祖先-后裔关系算法的时间复杂度仅为O(log n),完全支持更新,并且编码长度较短。     

支持数据更新的压缩编码研究

提出一种支持数据更新的XML压缩编码CXSU（Compact XML storage for Supporting Update processing）。CXSU编码将节点路径信息进行分解,避免了记录重复信息,同时支持节点祖先后代关系,父子关系和兄弟关系的表示。实验表明CXSU编码能节省存储空间,有效地支持XML数据动态更新。     

BSC：一种高效的动态XML树编码方案

确定一篇XML文档中任意两个节点之间是否存在某种结构关系,是XML查询处理过程的一个重要组成部分.XML树编码方案为每个节点分配唯一编号,仅通过比较节点编号而不必访问原XML文档,就可以快速有效地确定节点间的结构关系.随着XML应用不断普及,能否高效地支持更新操作,已成为XML树编码方案研究的一个重要课题.本文基于二进制小数的特性,提出了一种新的XML树编码方案-BSC,它可以完全高效地支持XML更新操作而不需要重新编码.实验结果证明,与已有的动态编码方案相比,BSC编码无论在静态编码方面还是在动态更新方面都具有很好的性能.     

支持XML插入更新的编码方法

对有序XML文档进行编码,可以不用访问XML数据文件就能够实现对XML数据的处理。目前提出的编码方案在支持查询XML数据方面取得了较好的效果,针对已有编码方案在插入更新过程中存在查询性能或者更新性能偏低等问题,提出了一种新的支持插入更新的编码方案——EDL,EDL对前缀编码进行了扩展,利用数值表达节点的初始顺序关系,利用二进制字符串(BS)来支持更新计算。EDL在未降低查询性能的前提下,完全避免了插入更新后对其他节点进行重新编码,高效实现了XML文档的插入更新计算。实验结果表明EDL优于同类型的支持更新的编码方案。     

一种高效的动态XML文档树编码机制

针对现有XML编码机制时空效率不高、对XML文档动态更新支持不够等问题,结合素数和IBSL 2种编码机制,提出一种新的XML文档树编码机制——基于素数的二进制字符串编码机制。理论分析和实验均证明该编码机制具有较好的查询效率,能够高效地支持XML文档更新操作,大幅降低空间成本。     

一种新的基于素数的XML动态编码方法

现有XML文档树编码存储空间较大,动态更新困难。结合DeweyBFN提出一种新的基于素数的XML动态编码方法。新方法采用子树域映射机制,避免使用较大素数,平均编码长度较小。理论分析和实验结果表明,该编码方法可以有效降低编码存储空间,具有较高的查询效率,支持XML数据的动态更新。     

An encoding scheme based on fractional number for querying and updating XML data

In order to facilitate the XML query processing, several labeling schemes have been proposed to directly determine the structural relationships between two arbitrary XML nodes without accessing the original XML documents. However, the existing XML labeling schemes have to re-label the pre-existing nodes or re-calculate the label values when a new node is inserted into the XML document during an update process. In this paper, we devise a novel encoding scheme based on the fractional number to encode the labels of the XML nodes. Moreover, we propose a mapping method to convert our proposed fractional number based encoding scheme to bit string based encoding scheme with the intention to minimize the label size and save the storage space. By applying our proposed bit string encoding scheme to the range-based labeling scheme and the prefix labeling scheme, the process of re-labeling the pre-existing nodes can be avoided when nodes are inserted as leaf nodes and sibling nodes without affecting the order of XML nodes. In addition, we propose an algorithm to control the increment of label size when new nodes are inserted frequently at a fix place of an XML tree. Experimental results show that our proposed bit string encoding scheme provides efficient support to the process of XML updating without sacrificing the query performance when it is applied to the range-based labeling schemes.     

A Dynamic Labeling Scheme for XML Document

Efficient evaluation of XML queries requires the determination of whether a relationship exists between two dements, A number of labeling schemes have been designed to meet the need. However, most of them have poor updating performance. In this paper, a new dynamic region-based labeling scheme is proposed which uses real numbers instead of integers to represent the region. Moreover, the scheme can adjust the codes of some nodes in some parts of the document tree according to the condition of updates. Our analysis shows this new labeling scheme provides efficient support for updates.     

基于扩展字节进位的动态XML树编码方案

为提高可扩展标记语言(XML)文档树编码的效率、支持XML数据动态更新,提出一种基于扩展字节进位的动态XML树编码方案(EBCL)。结合前缀编码和加法运算的思想,采用分段与分节的方式组成编码,给出静态前缀编码与动态前缀编码的算法流程。对编码大小与静态动态性能进行测试,实验结果表明,EBCL编码性能较优,能高效地支持XML文档的动态更新。     

一种支持数据更新的前缀编码方案

目前大部分前缀编码方案都不能很好的支持XML文档的数据更新.提出的前缀编码方案不仅能高效地支持结构查询,快速准确的判断XML文档结构树中任意两个结点之间的父子、先后代以及兄弟关系,而且对插入的结点采用新的编码规则,避免了更新操作带来的编码调整问题,能有效支持XML文档更新.     

Indexing and querying XML using extended Dewey labeling scheme

Finding all the occurrences of a tree pattern in an XML database is a core operation for efficient evaluation of XML queries. The Dewey labeling scheme is commonly used to label an XML document to facilitate XML query processing by recording information on the path of an element. In order to improve the efficiency of XML tree pattern matching, we introduce a novel labeling scheme, called extended Dewey, which effectively extends the existing Dewey labeling scheme to combine the types and identifiers of elements in a label, and to avoid the scan of labels for internal query nodes to accelerate query processing (in I/O cost). Based on extended Dewey, we propose a series of holistic XML tree pattern matching algorithms. We first present TJFast to answer an XML twig pattern query. To efficiently answer a generalized XML tree pattern, we then propose GTJFast, an optimization that exploits the non-output nodes. In addition, we propose TJFastTL and GTJFastTL based on the tag + level data partition scheme to further reduce I/O costs by level pruning. Finally, we report our comprehensive experimental results to show that our set of XML tree pattern matching algorithms are superior to existing approaches in terms of the number of elements scanned, the size of intermediate results and query performance.     

VEMBP:支持更新的XML树编码方法

对有序XML文档树进行编码,不需要访问XML原始文件就能够实现对XML数据的管理,提高了XML管理系统的效率。针对查询提出的编码方案具有很高的查询性能,但更新效率很低。为提高更新性能而设计的方案存在查询效率低或者编码空间大等问题。为了在提高更新XML文档效率的同时不对查询性能和编码空间产生负面影响,提出了一种新的编码方法VEMBP(Vector Encoding Method Based of Prime),该方法利用向量表示有序XML节点之间的顺序关系,采用素数表示有序XML文档节点之间的结构信息;并设计了一种算法来实现在没有牺牲查询性能的前提下完全避免更新过程中的二次编码和重新计算,降低了更新代价,同时编码空间也得到了控制。实验结果显示,VEMBP具有较好的查询和更新性能。     

Dynamic interval-based labeling scheme for efficient XML query and update processing

XML data can be represented by a tree or graph structure and XML query processing requires the information of structural relationships among nodes. The basic structural relationships are parent-child and ancestor-descendant, and finding all occurrences of these basic structural relationships in an XML data is clearly a core operation in XML query processing. Several node labeling schemes have been suggested to support the determination of ancestor-descendant or parent-child structural relationships simply by comparing the labels of nodes. However, the previous node labeling schemes have some disadvantages, such as a large number of nodes that need to be relabeled in the case of an insertion of XML data, huge space requirements for node labels, and inefficient processing of structural joins. In this paper, we propose the nested tree structure that eliminates the disadvantages and takes advantage of the previous node labeling schemes. The nested tree structure makes it possible to use the dynamic interval-based labeling scheme, which supports XML data updates with almost no node relabeling as well as efficient structural join processing. Experimental results show that our approach is efficient in handling updates with the interval-based labeling scheme and also significantly improves the performance of the structural join processing compared with recent methods.