XML流管理研究综述

近年来,XML流管理是数据流研究领域中的一个热点研究问题.不同于传统数据库管理系统,XML数据流管理系统需要在使用少量内存的情况下随时处理在线到达的数据流;由于XML流具有递归的、层次的结构,并且用户兴趣通常用XML查询语言来表示,因此,XML流管理技术与关系型数据流(基于元组的数据)管理技术有很大不同.综述XML流管理技术及各项研究成果;指出XML流管理系统的特点;比较了当前典型的XML数据流管理系统;系统地阐述和分析当前国内外已有的XML流数据处理方法(包括基于自动机的方法、基于索引的方法,基于序列的方法)和流处理的相关优化技术;指出尚需进一步研究的问题.     

XML数据流主动服务系统的设计与实现

从传统XML数据流查询处理中存在的问题出发，设计了XML数据流主动服务系统的框架模型，并提出了系统的实现策略，为用户快速、准确的找到所需信息提供了途径。     

Efficiently supporting order in XML query processing

XML is an ordered data model and XQuery expressions return results that have a well-defined order. However, little work on how order is supported in XML query processing has been done to date. In this paper we study the issues related to handling order in the XML context, namely challenges imposed by the XML data model, the variety of order requirements of the XQuery language, and the need to maintain order in the presence of updates to the XML data. We propose an efficient solution that addresses all these issues. Our solution is based on a key encoding for XML nodes that serves as node identity and at the same time encodes order. We design rules for encoding order of processed XML nodes based on the XML algebraic query execution model and the node key encoding. These rules do not require any actual sorting for intermediate results during execution. Our approach enables efficient order-sensitive incremental view maintenance as it makes most XML algebra operators distributive with respect to bag union. We prove the correctness of our order encoding approach. Our approach is implemented and integrated with Rainbow, an XML data management system developed at WPI. We have tested the efficiency of our approach using queries that have different order requirements. We have also measured the relative cost of different components related to our order solution in different types of queries. In general the overhead of maintaining order in our approach is very small relative to the query processing time.     

带Order子句的XQuery在XML流上的查询实现

随着XML的广泛应用,使得作为XML文档查询语言的XQuery成为人们研究的热点问题.将复杂XQuery在XML数据流上的查询应用于服务器/客户端模式来满足高效、实时查询的要求,所实现的XQuery查询原型系统XSIEQ支持嵌套、order子句的多关键字排序等.一次典型的XQuery查询过程可分为XPath查询、查询后处理两个阶段,本文着重描述查询后处理过程,最后给出了XSIEQ和Qizx在查询后处理时间性能上的对比及分析.     

基于XML的案例推理技术及其在生产调度中的应用研究

在广泛应用的案例推理技术中,非结构化案例占重要地位。针对非结构化案例的特点和相应的检索、匹配与推理机制,本文提出了基于XML的非结构化案例表示与推理技术。以天然气生产调度为例,详细介绍了非结构化案例的XML表示以及基于XQuery的案例检索、匹配与例修正过程。     

Developing an efficient query system for encrypted XML documents

XQuery is a query and functional programming language that is designed for querying the data in XML documents. This paper addresses how to efficiently query encrypted XML documents using XQuery, with the key point being how to eliminate redundant decryption so as to accelerate the querying process. We propose a processing model that can automatically translate the XQuery statements for encrypted XML documents. The implementation and experimental results demonstrate the practicality of the proposed model.     

基于DOM的XML数据库的索引技术研究

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。     

An efficient infrastructure for native transactional XML processing

Implementation techniques for relational database management systems (DBMSs) have proven their efficiency and robustness in many existing systems. However, many of these concepts and mechanisms cannot be used when implementing a native XML DBMS (XDBMS) because of substantial differences in the processing properties of natively stored XML documents as compared to relational tables. Therefore, we have to develop new and appropriate techniques with ACID transaction guarantees tailored to the processing characteristics of tree documents and the operations on them.

For this reason, we want to provide for an efficient infrastructure of XDBMSs consisting of tree node addressing and indexing together with fine-grained locking of tree nodes. In this respect, our prime and novel contribution is to reveal the potential of our prefix-based node labeling called DeweyIDs supporting record addressing, indexing, and locking protocols. In this paper, we first sketch our version of prefix-based node labeling and summarize a quantitative study on them. An overview of our layered XDBMS architecture indicates the concepts and functionalities to be reused from relational DBMS implementations. The core part of the paper describes the infrastructural services for XML document storage with compressed DeweyIDs, the principles and methods for navigational and declarative processing of queries, as well as the lock modes and protocols to enable efficient collaboration. Selected empirical experiments evaluate the XTC system performance and support our system assessment.     

An efficient XML encoding and labeling method for query processing and updating on dynamic XML data

In this paper, we propose an efficient encoding and labeling scheme for XML, called EXEL, which is a variant of the region labeling scheme using ordinal and insert-friendly bit strings. We devise a binary encoding method to generate the ordinal bit strings, and an algorithm to make a new bit string inserted between bit strings without any influences on the order of preexisting bit strings. These binary encoding method and bit string insertion algorithm are the bases of the efficient query processing and the complete avoidance of re-labeling for updates. We present query processing and update processing methods based on EXEL. In addition, the Stack-Tree-Desc algorithm is used for an efficient structural join, and the String B-tree indexing is utilized to improve the join performance. Finally, the experimental results show that EXEL enables complete avoidance of re-labeling for updates while providing fairly reasonable query processing performance.     

XML数据流主动服务系统的设计与实现

从传统XML数据流查询处理中存在的问题出发,设计了XML数据流主动服务系统的框架模型,并提出了系统的实现策略,为用户快速、准确的找到所需信息提供了途径。     

Distributed XML processing: Theory and applications

Basic message processing tasks, such as well-formedness checking and grammar validation, common in Web service messaging, can be off-loaded from the service providers’ own infrastructures. The traditional ways to alleviate the overhead caused by these tasks is to use firewalls and gateways. However, these single processing point solutions do not scale well. To enable effective off-loading of common processing tasks, we introduce the Prefix Automata SyStem — PASS, a middleware architecture which distributively processes XML payloads of web service SOAP messages during their routing towards Web servers. PASS is based on a network of automata, where PASS-nodes independently but cooperatively process parts of the SOAP message XML payload. PASS allows autonomous and pipelined in-network processing of XML documents, where parts of a large message payload are processed by various PASS-nodes in tandem or simultaneously. The non-blocking, non-wasteful, and autonomous operation of PASS middleware is achieved by relying on the prefix nature of basic XML processing tasks, such as well-formedness checking and DTD validation. These properties ensure minimal distributed processing management overhead. We present necessary and sufficient conditions for outsourcing XML document processing tasks to PASS, as well as provide guidelines for rendering suitable applications to be PASS processable. We demonstrate the advantages of migrating XML document processing, such as well-formedness checking, DTD parsing, and filtering to the network via event driven simulations.     

Active rules for XML: A new paradigm for E-services

XML is rapidly becoming one of the most widely adopted technologies for information exchange and representation. As the use of XML becomes more widespread, we foresee the development of active XML rules, i.e., rules explicitly designed for the management of XML information. In particular, we argue that active rules for XML offer a natural paradigm for the rapid development of innovative e-services. In the paper, we show how active rules can be specified in the context of XSLT, a pattern-based language for publishing XML documents (promoted by the W3C) which is receiving strong commercial support, and Lorel, a query language for XML documents that is quite popular in the research world. We demonstrate, through simple examples of active rules for XSLT and Lorel, that active rules can be effective for the implementation of e-commerce services. We also discuss the various issues that need to be considered in adapting the notion of relational triggers to the XML context. Received: 30 October 2000 / Accepted: 19 December 2000 Published online: 27 April 2001     

基于XML的数据集成系统实现

为了解决传统异构数据系统中数据查询处理不方便、信息之间交互利用困难、处理过程中没有统一的数据表现格式等问题,提出了一种基于XM L技术来进行数据集成的系统-基于XM L的学生信息集成系统,该系统采用XM L技术和Java技术相结合,查询处理上采用X query作为全局查询语言,满足了用户对数据集成和利用的各个层次的处理需求。实验结果表明,该系统达到了集成共享的目的,查询效率较高。     

Updating XML views published over relational databases: Towards the existence of a correct update mapping

XML data management using relational database systems has been intensively studied in the last few years. However, in order for such systems to be viable, they must support not only queries, but also updates over virtual XML views that wrap the relational data. While view updating is a long-standing difficult issue in the relational context, the flexible XML data model and nested XML query language both pose additional challenges for view updating.

This paper addresses the question, if for a given update over an XML view, a correct relational update translation exists. First, we propose a clean extended-source theory as criteria for determining whether a given translation mapping is correct. To determine the existence of such a correct mapping, we classify a view update as either un-translatable, conditionally or unconditionally translatable under a given update translation policy. This classification depends on several features of the XML view and the update: (a) granularity of the update at the view side, (b) properties of the view construction, and (c) types of duplication appearing in the view. These features are represented in the Annotated Schema Graph. This is further utilized by our Schema-driven Translatability Reasoning algorithm (STAR) to classify a given update into one of the three above update categories. The correctness of the algorithm is proven using our clean extended-source theory. This technique represents a practical approach that can be applied by any existing view update system in industry and academia for analyzing the translatability of a given update statement before translation of it is attempted. To illustrate the working algorithm, we provide a concrete case study on the translatability of XML view updates.     

Attribute grammars for scalable query processing on XML streams

We introduce the notion of XML Stream Attribute Grammars (XSAGs). XSAGs are the first scalable query language for XML streams (running strictly in linear time with bounded memory consumption independent of the size of the stream) that allows for actual data transformations rather than just document filtering. XSAGs are also relatively easy to use for humans. Moreover, the XSAG formalism provides a strong intuition for which queries can or cannot be processed scalably on streams. We introduce XSAGs together with the necessary language-theoretic machinery, study their theoretical properties such as expressiveness and complexity, and discuss their implementation.     

Studying the XML Web: Gathering Statistics from an XML Sample

XML has emerged as the language for exchanging data on the web and has attracted considerable interest both in industry and in academia. Nevertheless, to date, little is known about the XML documents published on the web. This paper presents a comprehensive analysis of a sample of about 200,000 XML documents on the web, and is the first study of its kind. We study the distribution of XML documents across the web in several ways; moreover, we provided a detailed characterization of the structure of real XML documents. Our results provide valuable input to the design of algorithms, tools and systems that use XML in one form or another. An erratum to this article is available at .     

PAM: A process algebra manipulator

PAM is a general proof tool for process algebras. It allows users to define their own calculi and then perform algebraic style proofs in these calculi by directly manipulating process terms. The logic thatPAM implements is equational logic plus recursion, with some features tailored to the particular requirements of process algebras. Equational reasoning is implemented by rewriting, while recursion is dealt with by induction. Proofs are constructed interactively, giving users the freedom to control the proof processes.     

Secure query processing against encrypted XML data using Query-Aware Decryption

Dissemination of XML data on the internet could breach the privacy of data providers unless access to the disseminated XML data is carefully controlled. Recently, the methods using encryption have been proposed for such access control. However, in these methods, the performance of processing queries has not been addressed. A query processor cannot identify the contents of encrypted XML data unless the data are decrypted. This limitation incurs overhead of decrypting the parts of the XML data that would not contribute to the query result. In this paper, we propose the notion of Query-Aware Decryption for efficient processing of queries against encrypted XML data. Query-Aware Decryption allows us to decrypt only those parts that would contribute to the query result. For this purpose, we disseminate an encrypted XML index along with the encrypted XML data. This index, when decrypted, informs us where the query results are located in the encrypted XML data, thus preventing unnecessary decryption for other parts of the data. Since the size of this index is much smaller than that of the encrypted XML data, the cost of decrypting this index is negligible compared with that for unnecessary decryption of the data itself. The experimental results show that our method improves the performance of query processing by up to six times compared with those of existing methods. Finally, we formally prove that dissemination of the encrypted XML index does not compromise security.     

XFlat: Query-friendly encrypted XML view publishing

The security of published XML data receives exceptional attention due to its sensitive nature in many applications. This paper proposes an XML view publishing method called XFlat. Compared with other methods, XFlat focuses on query performance over the published XML view while simultaneously protecting the sensitive data via encryption techniques. XFlat decomposes an XML tree into a set of sub-trees, in each of which multiple users have the same accessibility to all nodes, and may encrypt and store each sub-tree in a flat, sequential manner. This storage strategy can avoid the nested encryption cost in view construction and the nested decryption cost in query evaluation. In addition, we discuss how to generate a user-specific schema and how to minimize the total space cost of the published XML view when considering the overhead of the relationships among the sub-trees. We also propose an XML schema index to enhance query performance over the final XML view. The experimental results demonstrate the effectiveness and efficiency of the proposed XFlat method.     

基于下推自动机的XML数据流递归查询研究

针对具有子孙轴(//)和谓词([])结构特征的XPath对具有不同递归深度的XML数据流进行递归查询处理问题,提出了基于下推自动机技术的处理方法,通过将XPath各类置步转化成相对应的处理模块,由算法将各类处理模块组合起来,建立了自上而下的树状查询模型.由于查询过程中将会发生多重匹配,从而会产生大量的匹配模式,该模型通过有效的匹配策略和缓存操作,对匹配模式进行保存及检验,成功地实现XML数据流递归查询.实验结果表明,该算法在性能上要优于传统方法.