The <xsl:key> element declares a named key which can be used elsewhere in the stylesheet with the key( ) function.
Syntax
<xsl:key name=NAME match=EXPRESSION use=EXPRESSION />
Required Attributes
name- Specifies a name for this key. Must be a QName.
match- Defines the nodes for which this key is applicable.
use- Specifies an XPath expression that will be used to determine the value of the key for each of the applicable nodes.
Optional Attributes
None.
Type
Top-level, must be the child of <xsl:stylesheet> or <xsl:transform>.
Defined
XSLT, section 12.2.
Gecko support
Supported.