The system-property function returns properties of the XSLT processor (the system). Three system properties, all in the XSLT namespace, are mandatory for XSLT processors. These are xsl:version, xsl:vendor, and xsl:vendor-url. The input string is evaluated as a QName and so must have the xsl: prefix, since this is the prefix associated with the XSLT namespace in the underlying XSLT stylesheet.
XSLT 1.0, XSLT 2.0, XSLT 3.0.
Specifies the property name, which can be any of the following: xsl:version, xsl:vendor, xsl:vendor-url.