XML数据的B树存储实现及更新

XML正逐渐成为 WWW数据表示和交换的标准 ,如何有效实现对于 XML数据的存储、查询及更新等操作是 XML 相关技术研究中的一个重要领域。本文首先简要介绍了我们的基于模式匹配的 XML 数据库系统 (DISXDBS)组成 ;然后研究了如何实现用 B树存储 XML 文档以及对其进行查询、更新等操作 ;最后与目前存在的几种 XML 文档的存储策略进行比较。     

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.     

OrientStore+: 一种支持高效更新的Native XML存储方法

XML数据在数据库中的存储模式对XML数据的查询、索引及更新有重要的影响.而目前许多XML存储方法在更新上都需要较高的代价.提出一种Native XML存储方法OrientStore ,可以完全保留XML树结构信息,同时还具有如下特点:1)易于对XML数据建立各种索引; 2)存储记录间相互独立,进行更新时,可以减少对XML存储及索引的修改,减小了更新的代价; 3)在Native XML数据库系统OrientX中实现了这种存储模式.另外,在这种存储模式基础上提出一种基于空间利用率的XML存储更新算法.并通过实验比较了在不同存储方法上的查询与更新效率.     

XML数据库更新语言的定义和实现

目前人们对XML数据的管理系统研究的焦点主要集中在XML数据的存储和查询,但作为完整的数据管理系统,还需要提供对XML数据库系统的更新操作。论文提出一种称为U_XMLSQL的针对XML数据库的更新语言,接着设计了一种高效的物理存储结构对XML数据进行关系存储,在此存储结构的基础上设计并实现了更新语言中定义的基本操作,最后通过实验验证此存储方法和更新算法的高效性。     

原生XML存储方案的数据更新机制

原生XML存储方案直接关系到查询处理和数据更新。目前的原生XML存储方案大多关注于查询处理而很少涉及对数据更新的支持。与关系表的更新不同,XML更新要考虑到节点的文档顺序。提出了一种新的原生XML存储更新机制,它既保持了节点的文档顺序,又使更新操作局限于一个页面之内,保证了更新的效率。通过引入前向链接记录和重定位记录,该更新机制使页面分裂时记录存储地址保持不变,避免了索引更新的I/O开销。通过实例说明该原生XML存储方案的数据更新机制是有效的。     

基于三叉链表的XML文档存储模型

XML文档进行高效编码、索引、查询的前提是数据的存储模型.针对XML的典型树状结构,文章提出一种基于三叉链表的XML文档存储模型.在此基础上,讨论了XML数据的查询、更新、插入、删除、结点关系判断等运算的实现,分析了相关算法的效率.     

报文解析工具中的XML数据字典

针对报文解析过程中存在的数据存储无序、查询和调用不便等问题,提出应用XML数据字典进行数据存储的方案。根据给定的数据表,设计XML形式的数据字典。实现XML字典数据的解析,能在可视化界面上进行数据存储、查询和调用等操作,并用类图描述数据字典的存储和调用过程。结果证明,使用XML形式的数据字典,系统存储结构清晰,查询方便。     

基于混合式数据模型的XML查询方案

从数据模型的角度分析了现有XML查询方法存在缺陷的原因,并提出了一种新颖的自导航式XML查询方案.查询方案先对XML数据模型进行了改进,构造了与数据模型相匹配的查询语言和查询算法.其中,数据模型依据XML文档中节点间的语义相关性对节点信息进行聚簇式存储;查询语言则利用简单语法表达复杂语义;查询算法则具备自导航能力,能帮助用户在不完全了解XML文档结构的情况下获得目标信息.     

(对象)关系数据库中XML文档的存储技术

XML逐渐成为Web上数据表示和数据交换的标准，随着Web上大量的数据用XML文档表示出来，有必要对这些XML文档进行存储和查询。目前大多数商业数据库产品都支持对XML文档的存储、查询、索引等操作，本文讨论了在ORDB中存储XML文档时所涉及的存储技术，比较了三大商业数据库产品（IBM DB2，Oracle9i,Microsoft SQL Server 2000)在存储XML文档时所采用的方法。     

基于O-D的XML编码及对信息查询与更新的支持

提出了一种基于区间表示的XML编码方式，设计了相应的关系存储模式，研究了该编码方式对信息查询和信息更新的支持。鉴于XML关系存储下信息更新的困难性，采用基于order-descendan(O-D)的XML编码方式，不仅可以完全支持XPath查询语言的13个查询轴的查询功能，而且通过简单的计算即可有效地支持XML数据的增加和删除，这种简单计算可以在关系存储模式下通过SQL语句方便地实现。     

A visual programming language for XML manipulation

XML data flow has reached beyond the world of computer science and has spread to other areas such as data communication, e-commerce and instant messaging. Therefore, manipulating this data by non-expert programmers is becoming imperative and has emerged two alternatives. On one hand, Mashups have emerged a few years ago, providing users with visual tools for web data manipulation but not necessarily XML specific. Mashups have been leaning towards functional composition but no formal definitions have yet been defined. On the other hand, visual languages for XML have been emerging since the standardization of XML, and mostly relying on querying XML data for extraction or structure transformations. These languages are mainly based on existing textual XML languages, they have limited expressiveness and do not provide non-expert programmers with means to manipulate XML data. In this paper, we define a generic visual language called XCDL based on Colored Petri Nets allowing non-expert programmers to compose manipulation operations. The XML manipulations range from simple data selection/projection to data modification (insertion, removal, obfuscation, etc.). The language is oriented to deal with XML data (XML documents and fragments), providing users with means to compose XML oriented operations. The language core syntax is presented here along with an implemented prototype based on it.     

A methodology for clustering XML documents by structure

The processing and management of XML data are popular research issues. However, operations based on the structure of XML data have not received strong attention. These operations involve, among others, the grouping of structurally similar XML documents. Such grouping results from the application of clustering methods with distances that estimate the similarity between tree structures. This paper presents a framework for clustering XML documents by structure. Modeling the XML documents as rooted ordered labeled trees, we study the usage of structural distance metrics in hierarchical clustering algorithms to detect groups of structurally similar XML documents. We suggest the usage of structural summaries for trees to improve the performance of the distance calculation and at the same time to maintain or even improve its quality. Our approach is tested using a prototype testbed.     

一种新的基于B~+树结构的XML元素的索引方法

提出了一种用于搜索XML文档的新的索引方法即RIST。通过采用代码化的结构序列(SES)来表示XML文档和XML查询,得出查询XML数据等同于查找子序列匹配。RIST采用树结构作为查询的基本单元,从而避免了代价高昂的连接操作。另外,RIST还在XML文档的内容和结构上提供了一个统一的索引,所以它的一个很明显的优势就是克服了仅仅根据内容或结构建立索引的弊端。实验表明RIST在支持结构查询上是一种高效的方法。     

一种新的基于B＋树结构的XML元素的索引方法

摘要：本文提出了一种用于搜索XML文档的新的索引方法即RIST。通过采用代码化的结构序列（SES）来表示XML文档和XML查询,我们得出查询XML数据等同于查找子序列匹配。RIST采用树结构作为查询的基本单元,从而避免了代价高昂的连接操作。另外,RIST还在XML文档的内容和结构上提供了一个统一的索引,所以它的一个很明显的优势就是克服了仅仅根据内容或结构建立索引的弊端。实验表明RIST在支持结构查询上是一种高效的方法。     

一种基于结构特征的XML数据查询方法

针对XML数据特有的树型结构模式，提出了一种将树型结构的XML数据和查询语句转化为特定格式的字符串，基于串匹配原理对结构复杂的XML数据进行查询的方法，避免了传统的基于路径的查询方式所必需的路径之间的连接（join）操作，从而提高查询效率。利用本文提出的编码方式，可以建立关于XML数据结构和数据内容舍为一体的索引。实验显示，本文使用的针对XML数据查询的方法比传统的基于连接操作的数据查询方式高效，且本方法具有良好的扩展性。     

XML data update management in XML-enabled database

With the increasing demand for a proper and efficient XML data storage, XML-Enabled Database (XEnDB) has emerged as one of the popular solutions. It claims to combine the pros and limit the cons of the traditional Database Management Systems (DBMS) and Native XML Database (NXD). In this paper, we focus on XML data update management in XEnDB. Our aim is to preserve the conceptual semantic constraints and to avoid inconsistencies in XML data during update operations. In this current era when XML data interchange mostly occurs in a commercial setting, it is highly critical that data exchanged be correct at all times, and hence data integrity in XML data is paramount. To achieve our goal, we firstly classify different constraints in XML documents. Secondly, we transform these constraints into XML Schema with embedded SQL annotations. Thirdly, we propose a generic update methodology that utilizes the proposed schema. We then implement the method in one of the current XEnDB products. Since XEnDB has a Relational Model as the underlying data model, our update method uses the SQL/XML as a standard language. Finally, we also analyze the processing performance.     

Collaborative clustering of XML documents

Clustering XML documents is extensively used to organize large collections of XML documents in groups that are coherent according to structure and/or content features. The growing availability of distributed XML sources and the variety of high-demand environments raise the need for clustering approaches that can exploit distributed processing techniques. Nevertheless, existing methods for clustering XML documents are designed to work in a centralized way. In this paper, we address the problem of clustering XML documents in a collaborative distributed framework. XML documents are first decomposed based on semantically cohesive subtrees, then modeled as transactional data that embed both XML structure and content information. The proposed clustering framework employs a centroid-based partitional clustering method that has been developed for a peer-to-peer network. Each peer in the network is allowed to compute a local clustering solution over its own data, and to exchange its cluster representatives with other peers. The exchanged representatives are used to compute representatives for the global clustering solution in a collaborative way. We evaluated effectiveness and efficiency of our approach on real XML document collections varying the number of peers. Results have shown that major advantages with respect to the corresponding centralized clustering setting are obtained in terms of runtime behavior, although clustering solutions can still be accurate with a moderately low number of nodes in the network. Moreover, the collaborativeness characteristic of our approach has revealed to be a convenient feature in distributed clustering as found in a comparative evaluation with a distributed non-collaborative clustering method.     

Static analysis of XML transformations in Java

XML documents generated dynamically by programs are typically represented as text strings or DOM trees. This is a low-level approach for several reasons: 1) traversing and modifying such structures can be tedious and error prone, 2) although schema languages, e.g., DTD, allow classes of XML documents to be defined, there are generally no automatic mechanisms for statically checking that a program transforms from one class to another as intended. We introduce XACT, a high-level approach for Java using XML templates as a first-class data type with operations for manipulating XML values based on XPath. In addition to an efficient runtime representation, the data type permits static type checking using DTD schemas as types. By specifying schemes for the input and output of a program, our analysis algorithm will statically verify that valid input data is always transformed into valid output data and that the operations are used consistently.     

基于关系代数的XML数据查询

XML渐已成为Web上数据表示和交换的通用语言。为了有效地利用大量的XML文档，需要研究XML数据查询技术。提出了基于关系代数的XML数据查询方法。XML子句可以用关系代数表达式表示，并通过关系代数操作得到查询结果。该方法为查询XML数据提供了一种简洁和有效的手段。     

XML文档相似性的仿真研究

XML文档相似性的计算是XML文档分类中的一个难题。文中描述了一种基于结构的方法，通过序列化模式挖掘方法，挖掘出两个文档之间的最大相似路径，从而可以通过计算最大相似的路径的节点数目和所有路径的节点数目的比值，得到两个文档之间的相似度。文章提出了一种新的最小化XML文档的方法，并且综合考虑了文档节点的语义相似度和结构相似度，从而进一步地提高了计算文档相似度的精度。实验表明，该方法有着良好的应用前景。