Tamino XQuery User Guide - Software AG Documentation

The Nuts and Bolts of XQuery
NodeTest
'*:name'
'*'
Description
according to the axis used: all element or attribute nodes in the
specified namespace with the specified local name (regardless
of namespace)
according to the axis used: all element or attribute nodes
Predicates
The last, optional part of a step is one or more predicates to filter the sequence of selected nodes
according to the predicate expression. This expression is always enclosed in square brackets [ and
]. A selected node is retained if the predicate truth value of the predicate expression evaluates to
"true".
The predicate truth value is derived by applying the following rules, in order:
1. If the value of the predicate expression is an atomic value of a numeric type, the predicate truth
value is true if the value of the predicate expression is equal to the context position, and is false
otherwise.
2. Otherwise, the predicate truth value is the effective boolean value of the predicate expression.
The effective boolean value of an expression is false if its operand is any of the following:
■ An empty sequence
■ The boolean value false
■ A zero-length value of type xs:string or xdt:untypedAtomic
■ numeric value that is equal to zero
Otherwise, fn:boolean returns "true".
The filtered node sequence is ordered according to the direction of the selected axis.
Data Types
The XQuery type system is much richer than that of XPath 1.0. It uses the built-in data types as
defined in XML Schema 1.0. The set of built-in data types consist of primitive types and derived
types. They fall roughly into these categories:
■ Boolean values (true and false)
■ Numbers: decimals, floating-point numbers with single and double precision
■ Character Strings
■ Data types for dates, times, and durations (two of which are not yet defined in XML Schema)
XQuery User Guide
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