Tamino XQuery User Guide - Software AG Documentation

The Nuts and Bolts of XQuery
Path Expressions
XQuery uses path expressions to locate nodes in a document tree in much the same way as XPath
1.0 defined it originally:
let $b := input()/bib/book/author
return $b/last
input()/patient//type
The first expression returns the last child element nodes of all author elements. The second expressions
returns all type elements that are descendant nodes of the patient element. Here, // is
the abbreviated syntax for /descendant-or-self::node()/.
The structure of a path expression has only slightly changed with regard to XPath 1.0: A path expression
consists of a sequence of steps which can be distinguished into general steps and location
steps. A general step is an expression that evaluates to a node sequence, e.g. the input() function
that delivers the document nodes of the current collection. It can only be the first step in a path
expression. A location step consists of three parts:
■ An axis, which specifies the relationship between the set of selected nodes and the context node,
■ A node test, which specifies type and/or name of the set of selected nodes, and
■ Zero or more predicates, which further restrict the set of selected nodes.
Axes
XQuery supports a number of axes. An axis originates in the context node and determines the
initial node sequence that is further refined by node tests and predicates. In XQuery and XPath
2.0, you can specify a path in either unabbreviated or abbreviated syntax. The following table lists
each axis along with its direction (normal document order or reverse document order) and a short
description. In the unabbreviated syntax, a double colon '::' follows the name of the axis.
Axis
Direction
Meaning
ancestor::
attribute::
child::
descendant::
descendant-or-self::
parent::
self::
reverse
all ancestor nodes (parent, grandparent,
great-grandparent, etc.)
implementation-defined attached attribute nodes
normal
normal
normal
reverse
normal
immediate child nodes (default axis)
all descendant child nodes
current node and all its descendant child nodes
parent node (or attaching node for attribute and
namespace nodes)
the current node
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