一种关系模式下转换XML文档查询的有效方法*

在用关系数据库进行存储和管理XML数据的系统中,将XQuery查询语句转换为相应的SQL查询语句是一个重要的挑战。且由于这种转换依赖于关系模式生成技术,这就要求各种生成技术构造自己的查询处理器。该方法使得SilkRoute算法适用于更多的技术,并针对存取XML顺序信息的需求,改进了SilkRoute中的数据结构和算法,使之能正确转换基于顺序信息的XQuery查询。     

基于XDR纲要的空间元数据存储策略

提出一种基于XDR纲要的空间元数据存储体系结构,建立XDR纲要,将以XML表达的空间元数据映射到SQL Server 2000关系数据库中,可以使用加注释XDR纲要的XML视图对应到数据库的查询,并以XML文件的形式返回查询结果。     

Detecting common subexpressions for multiple query optimization over loosely-coupled heterogeneous data sources

The research presented in this paper supports the identification of common subexpressions as candidates for potential materialized views that form the basis of multiple query optimization in a loosely-coupled distributed system where query expressions access heterogeneous data sources, including relations and data-centric XML. This paper introduces a unifying mixed multigraph formalism to represent SQL, XQuery, and LINQ queries in a common query graph model and a heuristics-based algorithm to detect common subexpressions. The identified common subexpressions represent an opportunity for defining a materialized view to avoid repeating computation. The common subexpressions may access only relations, only XML, or a combination of relations and XML. The mixed multigraph model and the heuristic rules presented in this paper have distinguished advantages over the existing approaches that consider only relational or XML data sources individually. The mixed multigraph model can present SQL, XQuery, and LINQ queries in a single graph model and the heuristic rules are designed to consider the identical and subsumed conditions at the same time. A prototype implementation of the algorithm illustrates the applicability of the approach using various examples from the research literature as well as scenarios over a Criminal Justice enterprise that include common subexpressions across relational and XML data sources.     

基于领域本体和关系模型的XML语义集成方法研究

由于缺乏足够的语义信息,不同模式的XML数据之间很难进行互操作。针对油气井工程中的XML数据集成需求,借助领域全局本体,提出一种模式无关的XML语义集成方法。该方法首先在XML Path路径与领域本体之间进行语义映射,屏蔽其模式差异;然后,按照模型映射方法将XML存储为关系数据;最后通过查询重写将SPARQL转换为SQL语句,实现语义查询。该方法对XML模式进行语义标注,利用关系数据库存储与查询XML数据,能有效处理领域XML数据的语义集成。     

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.     

VIREX and VRXQuery: interactive approach for visual querying of relational databases to produce XML

VIREX provides an interactive approach for querying and integrating relational databases to produce XML documents and the corresponding schemas. VIREX connects to each database specified by the user; analyzes the catalogue to derive an interactive diagram equivalent to the extended entity-relationship diagram; allows the user to display sample records from the tables in the database; allows the user to rename columns and relations by modifying directly the interactive diagram; facilitates the conversion of the relational database into XML; and derives the XML schema. VIREX works even when the catalogue of the relational database is missing; it extracts the required catalogue information by analyzing the database content. Further, VIREX supports VRXQuery, which is a visual naive-users-oriented query language that allows users to specify queries and define views directly on the interactive diagram as a sequence of mouse clicks with minimum keyboard input. The user is expected to interactively decide on certain factors to be considered in producing the XML result. Such factors include: 1) selecting the relations/attributes to be converted into XML; 2) specifying a predicate to be satisfied by the information to be converted into XML; 3) deciding on the order of nesting between the relations to be converted into XML; 4) ordering for the result. VRXQuery supports selection, projection, nesting/join, union, difference, and order-by. As the result of a query, VIREX displays on the screen the XML schema that satisfies the specified characteristics and generates colored (easy to read) XML document(s). Further, VIREX allows the user to display and review the SQL and XQuery equivalent to each query expressed in VRXQuery.     

XTRON: An XML data management system using relational databases

Recently, there has been plenty of interest in XML. Since the amount of data in XML format has rapidly increased, the need for effective storage and retrieval of XML data has arisen. Many database researchers and vendors have proposed various techniques and tools for XML data storage and retrieval in recent years. In this paper, we present an XML data management system using a relational database as a repository. Our XML management system stores XML data in a schema independent manner, and translates a comprehensive subset of XQuery expressions into a single SQL statement. Also, our system does not modify the relational engine. In this paper, we also present the experimental results in order to demonstrate the efficiency and scalability of our system compared with well-known XML processing systems.     

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。     

Schema mapping and query translation in heterogeneous P2P XML databases

Peers in a peer-to-peer data management system often have heterogeneous schemas and no mediated global schema. To translate queries across peers, we assume each peer provides correspondences between its schema and a small number of other peer schemas. We focus on query reformulation in the presence of heterogeneous XML schemas, including data–metadata conflicts. We develop an algorithm for inferring precise mapping rules from informal schema correspondences. We define the semantics of query answering in this setting and develop query translation algorithm. Our translation handles an expressive fragment of XQuery and works both along and against the direction of mapping rules. We describe the HePToX heterogeneous P2P XML data management system which incorporates our results. We report the results of extensive experiments on HePToX on both synthetic and real datasets. We demonstrate our system utility and scalability on different P2P distributions.     

基于XQuery实现XML高效查询的分析研究

当愈来愈多的数据资料以XML为标准格式进行存储时,由于其格式的不同而导致传统的数据库及查询语法无法适用,该文分析了一种全新的XML查询语言XQuery,并对其在相关领域的应用作了介绍和比较。最后,对XQuery的发展前景作出展望。     

基于Shrex的XQuery-SQL查询转换模型的设计与实现

目前还没有一个不依赖于模式映射、且支持复杂嵌套XQuery到SQL的查询转换解决方案.针对现状,设计并实现了一个将XQuery转换为等价SQL的查询转换模型(EXSM).该模型基于Shrex框架,以简洁的方式解决了模式依赖问题,并采用树形中间结构,使之支持复杂的嵌套XQuery.因此,该模型有效地涵盖解决了目前存在的两个问题.     

基于XQuery实现XML高效查询的分析研究

当愈来愈多的数据资料以XML为标准格式进行存储时,由于其格式的不同而导致传统的数据库及查询语法无法适用,该文分析了一种全新的XML查询语言XQuery,并对其在相关领域的应用作了介绍和比较。最后,对XQuery的芡展前景作出展望。     

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。     

S2CX: From relational data via SQL/XML to (Un-)Compressed XML

The gap between storing data in relational databases and transferring data in form of XML has been closed e.g. by SQL/XML queries that generate XML data out of relational data sources. However, only few relational database systems support the evaluation of SQL/XML queries. And even in those systems supporting SQL/XML, the evaluation of such queries is quite slow compared to the evaluation of SQL queries. In this paper, we present S2CX, an approach that allows to efficiently evaluate SQL/XML queries on any relational database system, no matter whether it supports SQL/XML or not. As a result to an SQL/XML query, S2CX supports different output formats ranging from plain XML to different compressed XML representations including a succinct encoding of XML data, schema-aware compressed XML to grammar compressed XML. In many cases, S2CX produces compressed XML as a result to an SQL/XML query even faster than the evaluation of SQL/XML queries into non-compressed XML as provided by Oracle 11 g and by DB2. Furthermore, our approach to query evaluation scales better, i.e., the larger the dataset, the faster is our approach compared to SQL/XML query evaluation in Oracle 11 g and in DB2.     

A fuzzy extension of the XPath query language

Today the current state of the art in querying XML data is represented by XPath and XQuery, both of which rely on Boolean conditions for node selection. Boolean selection is too restrictive when users do not use or even know the data structure precisely, e.g. when queries are written based on a summary rather than on a schema. In this paper we describe a XML querying framework, called FuzzyXPath, based on Fuzzy Set Theory, which relies on fuzzy conditions for the definition of flexible constraints on stored data. A function called “deep-similar” is introduced to replace XPath’s typical “deep-equal” function. The main goal is to provide a degree of similarity between two XML trees, assessing whether they are similar both structure-wise and content-wise. Several query examples are discussed in the field of XML based metadata for e-learning.     

以XML文档发布关系数据

本文对以XML文档发布关系数据的新技术进行了综述，主要分析了两种发布关系数据到XML文档的语言描述及其实现技术，以及它们的优缺点，一种是利用并扩展SQL的功能来描述这种转换，嵌套的SQL表达式被利用来描述嵌套，扩展的SQL标量及聚集函数被利用来描述XML元素构造，实现将关系数据转换为XML文档，另一种是利用RXL（Relational to XML Transformation Language)语言来定义一个关系数据库的XML视图，该XML视图是虚的，其它应用可再利用XML查询语言XML－QL在虚拟的视图上构造一个查询，抽取XML视图中的数据片断并对抽取的部分进行物化，实现将关系数据转换为XML文档。     

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。     

基于查询的XML数据库设计

随着——XML半结构数据的使用日益增加,处理超大型数据集时,查询效率可能是个问题。就这个问题,首先探讨了XML、XQuery及原生XML数据库的关系,然后给出了设计原生XML数据库的一些原则,其恰恰与关系型数据库相反,然而,在存储介质不再是信息瓶颈的现在,这些准则对提高查询效率有着重要的意义。     

Growing triples on trees: an XML-RDF hybrid model for annotated documents

Since the beginning of the Semantic Web initiative, significant efforts have been invested in finding efficient ways to publish, store, and query metadata on the Web. RDF and SPARQL have become the standard data model and query language, respectively, to describe resources on the Web. Large amounts of RDF data are now available either as stand-alone datasets or as metadata over semi-structured (typically XML) documents. The ability to apply RDF annotations over XML data emphasizes the need to represent and query data and metadata simultaneously. We propose XR, a novel hybrid data model capturing the structural aspects of XML data and the semantics of RDF, also enabling us to reason about XML data. Our model is general enough to describe pure XML or RDF datasets, as well as RDF-annotated XML data, where any XML node can act as a resource. This data model comes with the XRQ query language that combines features of both XQuery and SPARQL. To demonstrate the feasibility of this hybrid XML-RDF data management setting, and to validate its interest, we have developed an XR platform on top of well-known data management systems for XML and RDF. In particular, the platform features several XRQ query processing algorithms, whose performance is experimentally compared.