DataDirect Technologies, Bedford, Mass., provides components for connecting software to data. Developers use these components to develop and deploy business applications across all major databases and platforms, and to connect those applications to a range of data sources.

XQuery or XML Query Language is a W3C specification (http://www.w3.org/TR/xquery) designed to provide a flexible and standardized way of searching through (semi-structured) data that is either physically stored as XML or virtualized as XML (such as XML Views over relational data). To give you an analogy, SQL is used to query relational data, XQuery is a standard language for querying XML data. In addition, XQuery also allows general processing of XML (such as creating nodes). Currently in the last call working draft status, the W3C XQuery specification will hopefully get the recommendation status this year. This article is an introduction to XQuery language. It is based on November 2003 working draft. (Click here to see the changes made to 23rd July 2004 XQuery 1.0 Working Draft.)

Everybody needs a home and now programmers working with XQuery have one on the Web. The xq:zone (http://xqzone.marklogic.com/) is sponsored by Mark Logic Corp., a San Mateo, Calif.-based developer of a database product for disparate content that makes extensive use of XQuery. The xq:zone is intended to provide help for developers working with the W3C standard for querying collections of XML data, including unstructured data, said Jason Hunter, lead applications engineer and XQuery guru at Mark Logic.

XQuery or XML Query Language is a W3C specification (http://www.w3.org/TR/xquery) designed to provide a flexible and standardized way of searching through (semi-structured) data that is either physically stored as XML or virtualized as XML (such as XML Views over relational data). To give you an analogy, SQL is used to query relational data, XQuery is a standard language for querying XML data. In addition, XQuery also allows general processing of XML (such as creating nodes). Currently in the last call working draft status, the W3C XQuery specification will hopefully get the recommendation status this year. This article is an introduction to XQuery language. It is based on November 2003 working draft.

XQuery 1.0 still has to reach W3C Recommendation status, but the available implementations and technology previews show that it is a very potent query language.

At Microsoft TechEd 2004 in San Diego, Microsoft provided further details on its upcoming database release now known as SQL Server 2005 (formerly code-named “Yukon”). The software will natively support Web services, XML and encryption.

Though XQuery is still a young language, it is important to look at the design choices of XQuery and find out the major influences on that design.

When you combine XML with URLs, great things happen. These two factors together make the endpoints of a transaction transparent to the kind of technologies that are on the other ends. However, this transparency can break down in the presence of databases. XQuery was proposed as a solution to this conundrum. Kurt Cagle looks at the structure and language of XQuery.

This chapter explores how XQuery provides a litany of navigation expressions. It is designed to be a language in which queries are concise and easily understood. It is also flexible enough to query a broad spectrum of XML information sources, including both databases and documents.

When you combine XML, which is essentially an open data format independent of any specific data-formatting language, with a universal addressing mechanism such as URLs, great things happen. These two factors together make the endpoints of a transaction transparent to the kind of technologies that are on the other ends.

Anyone who has ever done a search query on the Internet is familiar with the phenomenon in which a single query pulls up more than a million possible search matches. This has to do with the fact that information is ultimately not linear, but rather is linked and interrelated in ways that can't be quantified easily through text searches.

In Part 1 we examined what XQuery is and saw some example XQuery syntax. In particular, we examined the FLWR expression. In this final part we'll look at Microsoft's .NET XQuery engine, and how to start using XQuery in ASP.NET today.

XQuery borrows path expressions from XPath. XQuery can be viewed as a generalization of XPath. Except for some obscure forms (mostly unusual "axis specifiers"), all XPath expressions are also XQuery expressions. For this reason the XPath specification is also being revised by the XQuery committee, with the plan that XQuery 1.0 and XPath 2.0 will be released about the same time.

XQuery is often described as a query language for processing XML databases. But it's also a very nice language for generating XML and HTML, including web pages. In this article we will look at XQuery from this angle.

Finding specific information contained in an XML document can be a challenge. However, XQuery can save you valuable time when searching XML documents. Review the essentials of this W3C specification in this introduction.

One of the more fun and readily available ways to experiment with XQuery is to extract data from some of the XML data files that applications have left on your hard drive. For example, Apple uses XML frequently as a file format. The new Apple presentation tool Keynote stores its presentation files as XML; this opens up the exciting opportunity to data-mine existing presentations and auto-generate new presentations. XQuery comes in handy on both fronts. For my demonstration, I'll use a hypothetical (and somewhat simplified) Apple iTunes data file shown in Listing 3. This file stores the internal representation of an iTunes music library.

In this installment of Practical XQuery I continue to discuss practical uses of XQuery, focusing this time on interactive web page generation. The sample application will display a list of books; based on user input, it will also display detailed information about the selected title.

XQuery has earned a reputation for being for one of the most cautiously developed and, therefore, slowest evolving W3C standards. A key reason is that there is little industry experience in the retrieval of information stored in XML. Many companies are still innovating in this field and are generating a good deal of empirical information that has to be processed and distilled before a satisfactory level of comfort with the XML querying problem is achieved.

The XQuery data model recognizes seven types of nodes. Learn how to take advantage of the data model in XQuery expressions.

XML blurs the distinctions between databases, documents, and messages, but it needs a powerful and elegant query language to reach its full potential. XPath does not go far enough. XQuery intends to be that language.