Each prefix in a qualified name is associated with a URI.
For example, all elements in XSLT 1.0 style sheets are associated with the http://www.w3.org/1999/XSL/Transform URI.
The customary prefix xsl is a shorthand for the longer URI
http://www.w3.org/1999/XSL/Transform.
You can't use the URI in the element name directly.