# Q: why only '&' and '<' are encoded, but not '>'?
# A: because it is not required according to XML spec.
#
# [http://www.w3.org/TR/REC-xml#syntax]
# The ampersand character (&) and the left angle bracket (<) may appear in
# their literal form only when used as markup delimiters, or within a comment,
# a processing instruction, or a CDATA section. If they are needed elsewhere,
# they must be escaped using either numeric character references or the
# strings "&amp;" and "&lt;" respectively. The right angle bracket (>) may be
# represented using the string "&gt;", and must, for compatibility, be # escaped using "&gt;" or a character reference when it appears in the
# string "]]>" in content, when that string is not marking the end of a
# CDATA section.