Java 2EE and XML Development

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XQuery 1.0: An XML Query Language


Describes the human-readable, expression-based form of Xquery.


XML Syntax for XQuery 1.0 (XQueryX)


Describes an XML-based variant of the XQuery language.

XQuery 1.0 is a human-readable, expression-based language built on concepts borrowed from many other languages, including SQL, XQL, and Object Query Language (OQL). There is also an XML-based variant of XQuery under development called XQueryX. We focus on the human-readable XQuery in this section.


Table 3.2 Types of XQuery 1.0 expressions


XQuery expression type


Description


Path expressions


An XPath string representing a specific node or set of nodes in an XML data tree. For example, //customers would return a set of all the customer nodes found in a document.


Element constructors


Templates for generating derived XML nodes by executing XQL statements. These are basically XML nodes with embedded XQL expressions that generate derived data when executed by an XQuery engine.


FLWR expressions


SQL-like structured statements containing some combination of FOR, LET, WHERE, and RETURN clauses. (Pronounced flower.)

Table 3.2 Types of XQuery 1.0 expressions (continued)


XQuery expression type


Description


Operators and functions


XQuery supports mathematical expressions, built-in functions such as text() and not(), as well as user-defined functions and function libraries.


Conditional expressions


XQuery supports an IF-THEN-ELSE construct for execution branching.


Quantified expressions


XQuery supports partial node set selection using the SOME keyword, and complete node set selection using the EVERY keyword.


Data type expressions


XQuery supports data type testing and modification expressions

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