encoding specifies the preferred character encoding that the XSLT processor should use to encode sequences of characters as
sequences of bytes; the value of the attribute should be treated case-insensitively; the value must contain only characters
in the range #x21 to #x7E (i.e. printable ASCII characters); the value should either be a charset registered with the Internet
Assigned Numbers Authority or start with X-
Examples (xslt:xml): Overview 14:2