xsl:perform-sort instruction takes a sequence as its input and
produces a sorted sequence as its output.
The input sequence may be specified either using the
select attribute, or using the
instructions contained within the
The sort criteria are specified using
xsl:sort elements as children of
xsl:perform-sort, in the usual way.
It's often useful to use
xsl:perform-sort inside a stylesheet function; the function
can return the sorted sequence as its result, and can be invoked directly from an XPath expression.