The xmlns:xsl="http://www.w3.org/1999/XSL/Transform" points to the official W3C XSLT namespace. If you use this
namespace, you must also include the attribute version="1.0".
XSLT 2.0, XPath 2.0, and XQuery 1.0, share the same functions library. There are over 100 built-in functions.
There are functions for string values, numeric values, date and time comparison, node and QName manipulation,
sequence manipulation, and more.