What is XQuery?

XQuery is a technology under development by the World Wide Web Consortium (W3C) that's designed to query collections of XML data -- not just XML files, but anything that can appear as XML, including relational databases. XQuery has broad support from IBM, Microsoft, and Oracle as well as application server vendors such as BEA and Software AG.

XQuery will become a W3C standard - and developers can be sure that the code will work among different products.

XQuery can be used to:

• Extract information to use in a Web Service
• Generate summary reports
• Transform XML data to XHTML
• Search Web documents for relevant information

A query in XQuery is an expression that:

• reads a sequence of XML fragments or atomic values
• returns a sequence of XML fragments or atomic values

The principal forms of XQuery expressions are:

• path expressions
• element constructors
• FLWOR ("flower") expressions
• list expressions
• conditional expressions
• quantified expressions
• data type expressions

Expressions are evaluated relative to a context:

• namespaces
• variables
• functions
• date and time
• context item (current node or atomic value)
• context position (in the sequence being processed)
• context size (of the sequence being processed)

  XQuery and XPath

XQuery 1.0 and XPath 2.0 share the same data model and support the same functions and operators. If you have already studied XPath you will have no problems with understanding XQuery.

Uses of XQuery

XQuery can be used to:

• Extract information to use in a Web Service
• Generate summary reports
• Transform XML data to XHTML
• Search Web documents for relevant information

References:         http://www.w3schools.com/