ZVON > References > XSLT Reference
Go to standard

Attribute: match (of element <key>)

Standard excerpt:

The match attribute is a Pattern; an xsl:key element gives information about the keys of any node that matches the pattern specified in the match attribute.It is an error for the value of the match attribute to contain a VariableReference. Examples (xslt:xml): Overview
53:11 54:12 55:12

Interactive xlab: [xsl:key]