共查询到20条相似文献,搜索用时 15 毫秒
1.
基于DOM的XML数据库的索引技术研究 总被引:12,自引:1,他引:11
XML作为一种数据交换的国际标准,已经贯穿于Internet应用的各个领域之中,如何快速准确地存储和查询XML数据的数据库技术是一个重要的研究课题。XML索引技术对XML数据库查询处理起着至关重要的作用,提出了基于DOM的XML数据库的索引技术(路径连接索引、值索引和引用索引),解决了传统的基于树的遍历的XML数据查询方法性能上的不足,并着重对处理含有谓词和引用关系等较复杂的查询路径的不同处理方法进行了对比和分析,还给出了索引空间利用率、查询性能和索引维护代价3个方面的标准测试结果,表明新的索引技术可以有效地提高查询处理效率。 相似文献
2.
Evaluation of Indexing Strategies for Possibilistic Queries Based on Indexing Techniques Available in Traditional RDBMS
下载免费PDF全文
![点击此处可从《国际智能系统杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A common way to implement a fuzzy database is on top of a classical relational database management systems (RDBMS). Given that almost all RDBMS provide indexing mechanisms to enhance classical query processing performance, finding ways to use these mechanisms to enhance the performance of flexible query processing is of enormous interest. This work proposes and evaluates a set of indexing strategies, implemented exclusively on top of classical RDBMS indexing structures, designed to improve flexible query processing performance, focusing in the case of possibilities queries. Results show the best indexing strategies for different data a query scenarios, offering effective ways to implement fuzzy data indexes on top of a classical RDBMS. 相似文献
3.
基于XDR纲要的空间元数据存储策略 总被引:1,自引:0,他引:1
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。 相似文献
4.
在不考虑硬件环境的情况下,XML数据在RDBMS中的存储技术从很大程度上决定了基于关系的XML数据查询效率。目前基于关系的XML存储方式分为两大类:模型映射方法(model-mapping approach)和结构映射方法(structure-mapping approach)。根据XML数据查询处理效率,文章讨论了相关XML存储方法的优点和不足,并归结出XML存储后续研究的两个方向:路径信息的多雏处理和数据修改的有效支持。 相似文献
5.
6.
《Information and Software Technology》2003,45(1):11-22
The inverted index is widely used in the existing information retrieval field. In order to support containment queries for structured documents such as XML, it needs to be extended. Previous work suggested an extension in storing the inverted index for XML documents and processing containment queries, and compared two implementation options: using an RDBMS and using an Information Retrieval (IR) engine. However, the previous work has two drawbacks in extending the inverted index. One is that the RDBMS implementation is generally much worse in the performance than the IR engine implementation. The other is that when a containment query is processed in an RDBMS, the number of join operations increases in proportion to the number of containment relationships in the query and a join operation always occurs between large relations. In order to solve these problems, we propose in this paper a novel approach to extend the inverted index for containment query processing, and show its effectiveness through experimental results. In particular, our performance study shows that (1) our RDBMS approach almost always outperforms the previous RDBMS and IR approaches, (2) our RDBMS approach is not far behind our IR approach with respect to performance, and (3) our approach is scalable to the number of containment relationships in queries. Therefore, our results suggest that, without having to make any modifications on the RDBMS engine, a native implementation using an RDBMS can support containment queries as efficiently as an IR implementation. 相似文献
7.
Patrick Kling M. Tamer ?zsu Khuzaima Daudjee 《Distributed and Parallel Databases》2011,29(5-6):445-490
Distributing data collections by fragmenting them is an effective way of improving the scalability of a database system. While the distribution of relational data is well understood, the unique characteristics of the XML data and query model present challenges that require different distribution techniques. In this paper, we show how XML data can be fragmented horizontally and vertically. Based on this, we propose solutions to two of the problems encountered in distributed query processing and optimization on XML data, namely localization and pruning. Localization takes a fragmentation-unaware query plan and converts it to a distributed query plan that can be executed at the sites that hold XML data fragments in a distributed system. We then show how the resulting distributed query plan can be pruned so that only those sites are accessed that can contribute to the query result. We demonstrate that our techniques can be integrated into a real-life XML database system and that they significantly improve the performance of distributed query execution. 相似文献
8.
XN-Store:一种原生XML数据库的存储方案 总被引:1,自引:0,他引:1
随着XML相关标准的推广与应用,Web上出现了大量的XML文档,为了进行有效的管理,有必要将XML文档存储到数据库中,存储方案已成为XML数据管理领域研究的一个重要课题,将XML文档映射为关系表,存储到传统的RDBMS中,会破坏XML数据的树形结构,造成查询效率的下降,提出了一种新的用于原生XML数据库的存储方案--XN-Store,该方案基于索引结构将XML节点作为记录直接存储到分页文件中,建立起持久化文档对象模型,从而保持了XML数据原有的树形结构.XN-Store不仅降低了XML文档的存储空间开销,而且实现了XML节点的快速串行化输出和访问操作.作为通用的原生XML存储方案,XN-Store支持各种二级索引的创建,以提高XML查询处理的效率,采用多种数据集,分别在XN-Store和先前的XML存储系统上进行实验,比较存储空间、存储时间、串行化时间和节点访问时间.实验结果表明,XN-Store是一种高性能的原生XML数据库存储方案. 相似文献
9.
10.
Due to the increase of XML-based applications, XML schema design has become an important task. One approach is to consider
conceptual schemas as a basis for generating XML documents compliant to consensual information of specific domains. However,
the conversion of conceptual schemas to XML schemas is not a straightforward process and inconvenient design decisions can
lead to a poor query processing on XML documents generated. This paper presents a conversion approach which considers data
and query workload estimated for XML applications, in order to generate an XML schema from a conceptual schema. Load information
is used to produce XML schemas which can respond well to the main queries of an XML application. We evaluate our approach
through a case study carried out on a native XML database. The experimental results demonstrate that the XML schemas generated
by our methodology contribute to a better query performance than related approaches.
相似文献
Ronaldo dos Santos MelloEmail: |
11.
We describe the Enosys XML integration platform, focusing on the query language, algebra, and architecture of its query processor. The platform enables the development of eBusiness applications in customer relationship management, e-commerce, supply chain management, and decision support. These applications often require that data be integrated dynamically from multiple information sources. The Enosys platform allows one to build (virtual and/or materialized) integrated XML views of multiple sources, using XML queries as view definitions. During run-time, the application issues XML queries against the views. Queries and views are translated into the XCQL algebra and are combined into a single algebra expression/plan. Query plan composition and query plan decomposition challenges are faced in this process. Finally, the query processor lazily evaluates the result, using an appropriate adaptation of relational database iterator models to XML. The paper describes the platform architecture and components, the supported XML query language and the query processor architecture. It focuses on the underlying XML query algebra, which differs from the algebras that have been considered by W3C in that it is particularly tuned to semistructured data and to optimization and efficient evaluation in a system that follows the conventional architecture of database systems. 相似文献
12.
半结构化数据与关系数据的比较研究 总被引:2,自引:0,他引:2
围绕将半结构化数据(XML)与关系数据的比较及两者在性能上问题,进行了一些讨论。并通过一个试验程序,具体考察了半结构化数据和关系数据在处理较大规模数据(1万条记录以上)时性能上的差异。最后,对于其在这个领域内的应用,给出了一些探讨性的结论。 相似文献
13.
Fusheng Wang Carlo Zaniolo Xin Zhou 《The VLDB Journal The International Journal on Very Large Data Bases》2008,17(6):1445-1463
Effective support for temporal applications by database systems represents an important technical objective that is difficult
to achieve since it requires an integrated solution for several problems, including (i) expressive temporal representations
and data models, (ii) powerful languages for temporal queries and snapshot queries, (iii) indexing, clustering and query optimization
techniques for managing temporal information efficiently, and (iv) architectures that bring together the different pieces
of enabling technology into a robust system. In this paper, we present the ArchIS system that achieves these objectives by
supporting a temporally grouped data model on top of RDBMS. ArchIS’ architecture uses (a) XML to support temporally grouped
(virtual) representations of the database history, (b) XQuery to express powerful temporal queries on such views, (c) temporal
clustering and indexing techniques for managing the actual historical data in a relational database, and (d) SQL/XML for executing
the queries on the XML views as equivalent queries on the relational database. The performance studies presented in the paper
show that ArchIS is quite effective at storing and retrieving under complex query conditions the transaction-time history
of relational databases, and can also assure excellent storage efficiency by providing compression as an option. This approach
achieves full-functionality transaction-time databases without requiring temporal extensions in XML or database standards,
and provides critical support to emerging application areas such as RFID. 相似文献
14.
Rebecca J. Cathey Steven M. Beitzel Eric C. Jensen David Grossman Ophir Frieder 《The Journal of supercomputing》2008,44(2):146-178
XML is a flexible and powerful tool that enables information and security sharing in heterogeneous environments. Scalable
technologies are needed to effectively manage the growing volumes of XML data. A wide variety of methods exist for storing
and searching XML data; the two most common techniques are conventional tree-based and relational approaches. Tree-based approaches
represent XML as a tree and use indexes and path join algorithms to process queries. In contrast, the relational approach
utilizes the power of a mature relational database to store and search XML. This method relationally maps XML queries to SQL
and reconstructs the XML from the database results. To date, the limited acceptance of the relational approach to XML processing
is due to the need to redesign the relational schema each time a new XML hierarchy is defined. We, in contrast, describe a
relational approach that is fixed schema eliminating the need for schema redesign at the expense of potentially longer runtimes.
We show, however, that these potentially longer runtimes are still significantly shorter than those of the tree approach.
We use a popular XML benchmark to compare the scalability of both approaches. We generated large collections of heterogeneous
XML documents ranging in size from 500 MB to 8 GB using the XBench benchmark. The scalability of each method was measured
by running XML queries that cover a wide range of XML search features on each collection. We measure the scalability of each
method over different query features as the collection size increases. In addition, we examine the performance of each method
as the result size and the number of predicates increase. Our results show that our relational approach provides a scalable
approach to XML retrieval by leveraging existing relational database optimizations. Furthermore, we show that the relational
approach typically outperforms the tree-based approach while scaling consistently over all collections studied.
相似文献
Ophir Frieder (Corresponding author)Email: |
15.
16.
随着XML技术的不断发展和成熟,如何有效的利用关系数据库技术存储和查询XML文档显得非常重要。提出了一种XML文档DTD到关系表格的两阶段转换法,先将DTD文件映射为XSchema模式,通过对XSchema模式的约束简化、内联、添加键约束、数据类型和属性转换得到能够在RDBMS中存储的关系模型,映射后XML文档信息不会发生丢失且能保持键约束。实例的成功转换表明了该方法的可行性。 相似文献
17.
让关系数据库支持XML数据存储和查询,是XML领域重要的研究分支.DM XML系统以关系数据库为平台,融合结构映射和模型映射,根据路径统计实现了路径分区的编码方案.提出了DM XML查询模式集的解析、验证和生成方法.集合中的模式对应唯一的约束节点LCA关系序对,该序对并能严格地转化为等价的SQL查询.从实验数据分析,表明了DM XML编码方案的合理性和路径查询的高效性. 相似文献
18.
XML数据的查询技术 总被引:31,自引:1,他引:31
XML规范已成为当前网络应用(包括数字图书馆、Web服务以及电子商务)中事实上的数据表达、交换的标准.针对XML数据的查询在当前XML数据管理研究中占有重要的地位,也是当前XML数据处理研究领域的热点方向,相关的研究文献有很多.根据查询模式描述的不同,将当前XML查询技术归入两大类:XML Query方式和XML IR方式.后者又进而可分以为3个子类:XML IR/keyword方式、XML IR/fragment和XML IR/query方式,并从中挑选出3个研究者关注的问题进行了简述,它们是:Twig查询模式的处理、SLCA(smallest lowest common ancestor)节点的获取以及对所获取的XML片段相似性的度量.以方便普通用户使用为准则探讨了相关XML查询技术的优、缺点,将如下4个问题作为需要进一步关注的研究内容:结构化关键字查询及相应的结构相似性度量方法,如何消除XML Query查询处理模式(包含XML IR/query)和XML IR/keyword查询处理模式间数据冗余的问题,XML Query查询方式的理论探讨及其实现以及针对特定应用的XML数据的有效管理. 相似文献
19.
Storing and querying XML documents using a RDBMS is a challenging problem since one needs to resolve the conflict between the hierarchical, ordered nature of the XML data model and the flat, unordered nature of the relational data model. This conflict can be resolved by the following XML-to-Relational mappings: schema mapping, data mapping and query mapping. In this paper, we propose: (i) a lossless schema mapping algorithm to generate a database schema from a DTD, which makes several improvements over existing algorithms, (ii) two linear data mapping algorithms based on DOM and SAX, respectively, to map ordered XML data to relational data. To our best knowledge, there is no published linear schema-based data mapping algorithm for mapping ordered XML data to relational data. Experimental results are presented to show that our algorithms are efficient and scalable. 相似文献
20.
提出一种将分布式数据库数据映射为符合用户要求的XML文档的描述语言——R2XL,在此基础上给出基于XML的分布式数据库集成系统,实现分布式数据库的透明访问和联合查询。对该系统中的查询处理、分布式数据库中的数据分片方法及相应的集成策略等关键问题进行了探讨。 相似文献