XML encoding names
Is there some reason why XML encoding names are different from IANA
registered MIME charset names? There seem some pretty gratuitous
differences between the preferred MIME names and names listed in the spec.
XML Name Preferred MIME name
There are also some syntactic differences between charset names and encoding
names. Charset names are stated to be case insensitive, and allow any
printable US ASCII character, although in the currently registered names the
only two characters that occur frequently that aren't allowed in XML
encoding names are underscore and colon.