Continuous and Progressive XML Query Processing and its Applications

Continuous and Progressive XML Query Processing and its Applications

Stéphane Bressan (National University of Singapore, Singapore), Wee Hyong Tok (National University of Singapore, Singapore) and Xue Zhao (National University of Singapore, Singapore)
DOI: 10.4018/978-1-60566-308-1.ch009
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Abstract

Since XML technologies have become a standard for data representation, a great amount of discussion has been generated by the persisting open issues and their possible solutions. In this chapter, the authors consider the design space for XML query processing techniques that can handle ad hoc and continuous XPath or XQuery queries over XML data streams. This chapter presents the state-of-art techniques in continuous and progressive XML query processing. They also discuss several open issues and future trends.
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Introduction

XML (extensible markup language) is now a standard for data dissemination and interchange. While, in most application domains, the amount of available data feeds or data streams, whether sensor or engineered data, is generally increasing, the data in particular is increasingly in XML format. To seize the opportunity created by the availability of such a wealth of network accessible timely data, modern applications need the capability to effectively and efficiently process queries to XML data streams.

From individual stock investors to large hedge fund traders, those watching the stock market are interested in monitoring activities of company stocks and derivatives in the light of other news and data related to companies and their business. An investor, considering both technical and fundamental analyses wants to know both volume and price, and sales and revenue figures of company and industry for the stocks in his portfolio of interest. For the purpose of illustration, we consider the following scenario: An investor poses a query that combines a data stream from the stock market (providing latest volume and price) with a data feed reporting fundamental data data (e.g. updated sales figures). The query is a combination of two streams, the stock market ticker (nyse.xml) and the fundamental data streams (sales.xml) as well as an XML document, the listing in the stock exchange (listing.xml) that provides the mapping of the stock ticker symbol to the company name. The XQuery below returns a set of elements resultTuple, which consists of the company name, ticker symbol, sales, last price, and volume of all the stocks in the exchange. (Figure 1)

Figure 1.

An XQuery query combining technical and fundamental data from live feeds for market monitoring

Reading new blogs is often disorienting as bloggers often assume that their readers are familiar with the news on which they are commenting. A possible solution is to automatically combine blog entries with headlines and provide the links to the related news. Both blogs entries and news are often available as RSS (really simple syndication) or atom feeds. Existing RSS/Atom readers provide basic keyword-based filtering and simple feed merging. Instead of relying on the limited capabilities of existing readers and their interface, and since the feeds are in XML, the desired combination can be expressed as an XQuery offering the full expressive power of a query language. Although RSS and Atom sources are more similar to Web pages being pulled than to feeds or streams pushing data, the latter can be simulated by periodic pulling. In the example at hand, the combination of blog entries and news can be achieved by the Xquery given in Figure 2.

Figure 2.

An XQuery query combining blog entries with their related news from RSS/Atom feeds

The number and scope of possible applications is limited only by our imagination. Their effective and efficient implementation depends on the availability of algorithms, techniques and tools for the processing of continuous and progressive queries to XML data streams. Unlike the processing of queries to XML repositories, applications processing XML data streams do not have a priori access to the complete data. This makes it difficult to index and organize data. At the same time, since data is transient, only limited memory is available for immediate processing. Since data arrives continuously, these applications need XML query processors that can efficiently process queries on-the-fly. In order to ensure a good user experience, the XML query processors must deliver initial results quickly, maintain a consistently high result throughput, and ensure that the produced results are representative. Since queries are themselves long running or continuous, the XML query processors should be able to exploit the opportunities to share computation and intermediate results among queries.

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Table of Contents
Foreword
Ernesto Damiani
Preface
Eric Pardede
Acknowledgment
Eric Pardede
Chapter 1
Mary Ann Malloy, Irena Mlynkova
As XML technologies have become a standard for data representation, it is inevitable to propose and implement efficient techniques for managing XML... Sample PDF
Closing the Gap Between XML and Relational Database Technologies: State-of-the-Practice, State-of-the-Art and Future Directions
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Chapter 2
Mirella M. Moro, Lipyeow Lim, Yuan-Chi Chang
It is well known that XML has been widely adopted for its flexible and self-describing nature. However, relational data will continue to co-exist... Sample PDF
Challenges on Modeling Hybrid XML-Relational Databases
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Chapter 3
Vassiliki Koutsonikola, Athena Vakali
Nowadays, XML has become the standard for representing and exchanging data over the Web and several approaches have been proposed for efficiently... Sample PDF
XML and LDAP Integration: Issues and Trends
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Chapter 4
Giovanna Guerrini, Marco Mesiti
The large dynamicity of XML documents on the Web has created the need to adequately support structural changes and to account for the possibility of... Sample PDF
XML Schema Evolution and Versioning: Current Approaches and Future Trends
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Chapter 5
Mingzhu Wei, Ming Li, Elke A. Rundensteiner, Murali Mani, Hong Su
Stream applications bring the challenge of efficiently processing queries on sequentially accessible XML data streams. In this chapter, the authors... Sample PDF
XML Stream Query Processing: Current Technologies and Open Challenges
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Chapter 6
Sven Groppe, Jinghua Groppe, Christoph Reinke, Nils Hoeller, Volker Linnemann
The widespread usage of XML in the last few years has resulted in the development of a number of XML query languages like XSLT or the later... Sample PDF
XSLT: Common Issues with XQuery and Special Issues of XSLT
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Chapter 7
Mirella M. Moro, Zografoula Vagena, Vassilis J. Tsotras
Content-based routing is a form of data delivery whereby the flow of messages is driven by their content rather than the IP address of their... Sample PDF
Recent Advances and Challenges in XML Document Routing
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Chapter 8
Philippe Poulard
XML engines are usually designed to solve a single class of problems: transformations of XML structures, validations of XML instances, Web... Sample PDF
Native XML Programming: Make Your Tags Active
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Chapter 9
Stéphane Bressan, Wee Hyong Tok, Xue Zhao
Since XML technologies have become a standard for data representation, a great amount of discussion has been generated by the persisting open issues... Sample PDF
Continuous and Progressive XML Query Processing and its Applications
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Chapter 10
Fabio Grandi, Federica Mandreoli, Riccardo Martoglia
In several application fields including legal and medical domains, XML documents are “versioned” along different dimensions of interest, whose... Sample PDF
Issues in Personalized Access to Multi-Version XML Documents
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Chapter 11
Tran Khanh Dang
In an outsourced XML database service model, organizations rely upon the premises of external service providers for the storage and retrieval... Sample PDF
Security Issues in Outsourced XML Databases
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Chapter 12
Marco Mesiti, Ernesto Jiménez Ruiz, Ismael Sanz, Rafael Berlanga Llavori, Giorgio Valentini, Paolo Perlasca, David Manset
There is a proliferation of research and industrial organizations that produce sources of huge amounts of biological data issuing from... Sample PDF
Data Integration Issues and Opportunities in Biological XML Data Management
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Chapter 13
Doulkifli Boukraa, Riadh Ben Messaoud, Omar Boussaid
Current data warehouses deal for the most part with numerical data. However, decision makers need to analyze data presented in all formats which one... Sample PDF
Modeling XML Warehouses for Complex Data: The New Issues
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Chapter 14
Irena Mlynkova
Since XML technologies have become a standard for data representation, numerous methods for processing XML data emerge every day. Consequently, it... Sample PDF
XML Benchmarking: The State of the Art and Possible Enhancements
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About the Contributors