双时态XML查询中now语义失真的研究与扩展

本文研究如何有效地查询基于"单属性表示时态信息"的XML文档的时态信息操作,并选择XML功能较为强大的查询语言XQuery进行时态查询扩展.文中先计论如何解决时态数据库中特殊元素now的语义失真的问题,然后对XQuery进行双时态扩展,最后给出扩展后的查询实例.     

XQuery视图机制

从XML数据安全性考虑，在已经使用XQuery作为查询语言的前提下，为增强XQuery对XML文档查询能力，创造了类似关系数据库视图的XQuery视图机制，使得不同用户对XML文档具有不同的查看能力，保证查询安全可靠。XQuery视图由查询来定义其内容，分为实视图和虚视图两种。虚视图根据需要计算视图定义的查询，而实视图不管以后是否需要，只要一创建就计算其视图定义，类似关系数据库视图，实视图和虚视图对于数据查询都是必要的。     

支持全文检索的XQuery查询处理及优化的研究

XQuery作为由W3C组织提出的一种XML查询语言,正在成为当前应用于XML数据库中对XML数据操作的一个规范。为了提高对XML中文本内容的查询支持,W3C又进一步设计了支持全文检索功能的语法规范。针对最新的XQuery及全文检索语法特征,文章提出了支持全文检索功能XQuery的解析与查询执行策略,为XQuery的查询处理提供解决方案。在此基础上,针对全文检索功能的查询执行计划,提出了适用于窗口查询,距离查询,是否排序查询的优化方案,以减少查询执行的代价,提高XQuery查询的效率。     

XQuery的应用分析

XML查询语言XQuery是导航语言XPath的扩展,它是一种语法简单灵活且表现力强大的功能性语言。XQuery与XML数据结构有内在的联系,可以方便地编写业务逻辑,并且本质上就可以操作XML数据。本文对XQuery发展状况的进行了概要介绍,通过查询语言XQuery的主要概念,及XQuery语言在数据查询、转换等方面的应用分析,对XML文档查询语言的实际应用情况作出讨论。     

XQuery的应用分析

XML查询语言XQuery是导航语言XPath的扩展,它是一种语法简单灵活且表现力强大的功能性语言。XQuery与XML数据结构有内在的联系,可以方便地编写业务逻辑,并且本质上就可以操作XML数据。本文对XQuery发展状况的进行了概要介绍,通过查询语言XQuery的主要概念,及XQuery语言在数据查询、转换等方面的应用分析,对XML文档查询语言的实际应用情况作出讨论。     

XQBE: A Graphical Environment to Query XML Data

XQuery, the standard query language for XML, is increasingly popular among computer scientists with SQL background, since XQuery and SQL require comparable skills. However, these experts are limited in number, and the availability of easier XQuery “dialects” could be extremely valuable. With this motivation in mind, we designed XQBE, a visual dialect of XQuery inspired by the QBE language (Query by Example). Coherent with the hierarchical nature of XML, XQBE uses one or more hierarchical structures to denote the input documents and one structure to denote the document produced in output. These structures are annotated to express selection predicates; explicit binding edges connecting the nodes of these structures visualize the input/output mappings. This paper presents XQBE through several examples and describes the main features of our implementation of the language, a visual editor coupled with an XQBE-to-XQuery translator. Indeed, the XQBE front-end is a general purpose user-friendly visual query interface, capable of providing access to any data storage system that exposes XQuery APIs. Available schema information can be exploited to guide users in querying data sets they are not familiar with. Also, switching between the visual and textual versions of the same query could be helpful for XQuery learners.     

XML数据查询语言XQuery应用分析

目前,XML已经成为事实上的数据表示和数据交换标准,XQuery是用来对XML文档进行数据查询的W3C候选推荐标准。结合XQuery规范的最新发展状况,介绍XQuery查询语言的主要特性,通过实例讨论XQuery语言在数据查询、转换等方面的应用。对SQL/XML和Xquery进行了比较,并分析了XQuery的实现与应用情况。     

集成XQuery功能的Xindice数据库

Xindice是一种原生XML数据库,提供了对XML的存储和管理功能.但Xindice只提供了XPath查询语言,不能灵活满足对XML的查询要求.提出了用Java语言实现XQuery的机制,并提出了将其集成到Xindice中的方法,有效地扩充了Xindice的查询功能.     

一种XQuery查询程序自动生成系统的设计与实现

设计并实现了一种XQuery查询程序自动生成系统.为普通用户提供一种界面友好的XQuery查询,有利于XML的进一步推广.     

An adaptive path index for XML data using the query workload

Due to its flexibility, XML is becoming the de facto standard for exchanging and querying documents over the Web. Many XML query languages such as XQuery and XPath use label paths to traverse the irregularly structured XML data. Without a structural summary and efficient indexes, query processing can be quite inefficient due to an exhaustive traversal on XML data. To overcome the inefficiency, several path indexes have been proposed in the research community. Traditional indexes generally record all label paths from the root element in XML data and are constructed with the use of data only. Such path indexes may result in performance degradation due to large sizes and exhaustive navigations for partial matching path queries which start with the self-or-descendent axis(“//”). To improve the query performance, we propose an adaptive path index for XML data (termed APEX). APEX does not keep all paths starting from the root and utilizes frequently used paths on query workloads. APEX also has a nice property that it can be updated incrementally according to the changes of query workloads. Experimental results with synthetic and real-life data sets clearly confirm that APEX improves the query processing cost typically 2–69 times compared with the traditional indexes, with the performance gap increasing with the irregularity of XML data.     

基于XML的异构多源数据查询

研究基于XML的异构多源数据查询处理方法.通过引入虚拟全局视图方式以及将LAV(local as view)方法应用于全局视图和局部视图的关系当中来实现异构多源数据查询处理.此外,还研究了支持XML查询处理的XQuery正规化规则及在不同情况下转换FLWR的策略.     

基于XML文档的图书信息XQuery查询技术

XML与HTML相比在数据管理和格式化组织上具有更大的优越性，XQuery能够有效地查询和处理XMI文档。为了查询网上基于XML文档的图书信息，文章设计了一些统一格式的XML文档作为图书信息的数据源，利用XQuery技术，将XQuery查询程序嵌入实现格式控制的JAVA程序中，JAVA程序可以调用并运行XQuery查询程序，查询的结果保存到一个XML文件中，将查询得到的XML文档转换成需要的格式输出给用户。初步实验证明这种方法是可行的并具有较强的实用性，为实现网上基于XML文档的信息查询提供了技术基础。     

用户界面友好的XML查询方案

提出一用户界面友好的XML文档查询方案，使普通Internet用户不必使用复杂的XML查询语言，也不必知道所查XML文档的精确结构，只须输入相关的已知条件和待求信息，就能够实现Web上XML文档的统一查询。     

XQuery简介及在.Net中的应用

XML是一种通用标记语言,它能对各种数据源的信息内容进行标记,包括结构化和半结构化文档、关系数据库和对象库,不管它们是物理存储在XML中还是通过中间产生展现为XML,都能够智能地使用XML结构化查询语言表达或查询这些类型数据。XQuery是定位于XML的查询语言,它能广泛应用于很多类型的XML数据源。     

基于XQuery的数据集成系统中的查询分解算法

XQucry查询语言使用XML作为抽象数据模型。可以对基于XML的数据源作查询，无论这些数据源是真正的XML文件或者是中间件提供的XML视图。本文研究了以XQuery作为查询语言的数据集成系统中的查询分解算法。在XQucry语言的层次，利用它的语言特点实现了多数据源的查询分解算法。     

并行XML数据库查询处理算法的性能评价

基于父子关系的并行流水线连接查询方法PCPPJ(Parallel Pipeline Joining based on Parent Child relationship)是一种在并行多处理机环境下,利用分布式对象数据库对XML进行并行查询的新方法,对这种并行XML查询方法的测试结果进行分析和说明.PCPPJ查询方法在长路径和大文档情况下有更好的查询效果.     

基于XML的虚拟数据库中间件的研究

针对目前大量的Web数据源不易使用及虚拟数据库中查询信息响应不及时的情况，本文阐述了构造一个虚拟数据库中间件的方法，采用XML为数据交换模式，以XQuery为查询语言，使得Web数据容易被访问，并且通过缓存系统和多线程机制提高查询效率。     

A survey on XML streaming evaluation techniques

XML is currently the most popular format for exchanging and representing data on the web. It is used in various applications and for different types of data including structured, semistructured, and unstructured heterogeneous data types. During the period, XML was establishing itself, data streaming applications have gained increased attention and importance. Because of these developments, the querying and efficient processing of XML streams has became a central issue. In this study, we survey the state of the art in XML streaming evaluation techniques. We focus on both the streaming evaluation of XPath expressions and of XQuery queries. We classify the XPath streaming evaluation approaches according to the main data structure used for the evaluation into three categories: automaton-based approach, array-based approach, and stack-based approach. We review, analyze, and compare the major techniques proposed for each approach. We also review multiple query streaming evaluation techniques. For the XQuery streaming evaluation problem, we identify and discuss four processing paradigms adopted by the existing XQuery stream query engines: the transducer-based paradigm, the algebra-based paradigm, the automata-algebra paradigm, and the pull-based paradigm. In addition, we review optimization techniques for XQuery streaming evaluation. We address the problem of optimizing XQuery streaming evaluation as a buffer optimization problem. For all techniques discussed, we describe the research issues and the proposed algorithms and we compare them with other relevant suggested techniques.     

An XML-Based Approach to Publishing and Querying the History of Databases

There is much current interest in publishing and viewing databases as XML documents. The general benefits of this approach follow from the popularity of XML and the tool set available for visualizing and processing information encoded in this universal standard. In this paper, we explore the additional and unique benefits achieved by this approach on temporal database applications. We show that XML with XQuery can provide surprisingly effective solutions to the problem of supporting historical queries on past content of database relations and their evolution. Indeed, using XML, the histories of database relations can be naturally represented by temporally grouped data models. Thus, we identify mappings from relations to XML that are most conducive to modeling and querying database histories, and show that temporal queries that would be difficult to express in SQL can be easily expressed in standard XQuery. This approach is very general, insofar as it can be used to store the version history of arbitrary documents and, for relational databases, it also supports queries on the evolution of their schema. Then, we turn to the problem of supporting efficiently the storage and the querying of relational table histories. We present an experimental study of the pros and cons of using native XML databases, versus using traditional databases, where the XML-represented histories are supported as views on the historical tables.     

XQuery实现技术研究综述

XML数据的广泛应用,使得高性能的XQuery实现成为XML数据处理领域的重要课题,但XQuery的灵活性和复杂性为其实现技术研究提出了巨大挑战。XQuery语言的高性能实现需要利用XML查询代数提供的查询优化方法,也需要采取高效的树模式整体匹配算法。给出了XQuery语言实现的基础架构,探讨了原生XML数据库系统中XQuery实现的关键技术——查询代数和树模式查询的国内外研究现状,展望了未来的研究方向及面临的挑战。