Question: how xsl stylesheet is declared?
Answer: Correct Style Sheet Declaration The root element that declares the document to be an XSL style sheet is <xsl:stylesheet> or <xsl:transform>. ... 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".