In SOA 11g, there is a new XSL-Construct for sorting the input nodes. This is a basic XSLT construct (element) which was missing earlier.
As the w3 standard defines, this construct cannot be used independently, but can be used along with xsl:for-each(or xsl:apply-templates)
It is used to sort the input data based upon some id or text(called as sort-key).
This can be very useful functionality in scenarios where one needs to process some data in a specific sequence.
For detail, please find more here