XQuery

Definition

Xquery is a query language that uses the structure of XML intelligently can express queries across all these kinds of data, whether physically stored in XML or viewed as XML via middleware. In other words, you can use it to retrieve things from files, from XML representations made from SQL databases, from native XML databases like exists. In addition, Xquery is quite a real programming language. XUpdate is a protocol to updated (XQuery can't). XML Databases are servers in which can plug XML "as is" and get it back with Xquery and/or XSLT.

Documentation

Standards

• XQuery 1.0: An XML Query Language (the central document). XQuery can only query (not update). There are some other parts, e.g.
  • XML Query Use Cases
  • XML Query Requirements
  • XML Query 1.0 and XPath 2.0 Data Model
  • XQuery 1.0 and XPath 2.0 Formal Semantics. Easy bedtime reading ;)
• xqupdate - XQuery Update Facility. (W3C Working Draft 28 August 2007). As of nov 2007, there are not many implementations for this replacement of Xupdate.
• Xpath 2.0 is used both by XSLT 2.0 and XQuery. XQuery is an extension of XPath 2.0 and both XSLT 2.0 and XQuery 2.0 share the same data model.
• Xupdate. Not a W3C standard, can be used to update some XML databases (not updated since 2000 an will be replaced by XML Query Update). Xupdate looks a lot like XSLT.

XQuery Tutorials

• XQuery (Wikipedia article)
• Essential XQuery - The XML Query Language by Darshan Singh. (Feb 2, 2004). Good !
• XQuery Tutorial by P. Fankhauser and P. Wadler.
• An introduction to XQuery, IBM Developer works (2002, updated 2006).
• XQuery, tutorial by Anders Möller & Michael I. Schwartzbach [2003]. See also:
  • Chapter 6 - Querying XML Documents with XQuery (slides) and their book An Introduction to XML and Web Technologies, ISBN 0321269667
• XQuery Tutorial from IPEDO. Quite technical.
• XQuery from the Experts: Influences on the design of XQuery Webreference Article, excerpt is from Chapter 2 of the Addison-Wesley book XQuery from the Experts. [2003]
• Michael Brundage (2004). XQuery: The XML Query Language, Portland: Book News [this is a good book]

Other

• XML:DB XUpdate Use Cases by Kimbro Staken. This document outlines a basic set of uses cases for the XUpdate specification from the XML:DB Initiative.

Software

XML databases

See XML database

XQuery Engines

• XQuery Engines, Processors, Providers A list of products by SQL Summit.com

• SAXON XSLT and XQuery Processor. There is a free version. (works).
• XQEngine - XML Query Engine implements XQuery - sourceforge project.
• MXQuery. low-footprint, extensible XQuery Engine (Java). Includes support for update
• Galax. open-source implementation of XQuery 1.0.
• Safari Guide Safari Guide is a free application for Mac OS X Tiger that allows developers to evaluate arbitrary XPath and XQuery expressions against the current frontmost Safari webpage. [10/2005]

XML Editors with XQuery support

See XML editor for a list of XML editors

Many, e.g. XML Exchanger lite.

Libraries

For eXist

• PheXist is a set of classes for PHP 5. (older version also for PHP4 & Perl) to query and manipulate XML documents in eXist XML:DB. (Version 0.5, april 2007). PHP 5 needs the soap extension enabled.
• XML_DB_eXist aka DB_eXist (dead ?)

Links

• XML Database Products by Ronald Bourret