XSLT, 2nd Edition

XPath Axes

The XPath specification defines 13 different axes; each axis contains various nodes. The nodes that are in a given axis depend on the context node. All 13 axes, excerpted from our more involved discussion in The XPath Data Model” in Chapter 3, are listed here.

child axis

Contains the children of the context node. As we’ve already mentioned, the XPath expressions child::lines/child::line and lines/line are equivalent. If an XPath expression (such as sonnet) doesn’t have an axis specifier, the child axis is used by default.

parent axis

Contains the parent of the context node, if there is one. (If the context node is the root node, the parent axis returns an empty node-set.) As a step in an XPath expression, the parent axis can be abbreviated with the double period (..); this moves up to the current node’s parent. If the <first-name> and <last-name> elements are both children of the <author> element, and the context node is the <first-name> element, the expressions ../last-name, parent::author/last-name and parent::*/last-name are equivalent. If the context node does not have a parent, this axis returns an empty node-set.

self axis

Contains the context node itself. As a step in an XPath expression, the self axis can be abbreviated with a single period (.). The expressions ., self::node(), and self::* are equivalent in XSLT 1.0.

[2.0] In XSLT 2.0, the self axis selects the context item, which might not be a node. If the context item is an atomic value, the expressions self::node() ...