I think it isn't a good idea to muck with the MIME format for
Content-Type or to restrict the available parameters, or to
add another parameter for "language-selection" which doesn't
exist in MIME. If you want to describe some content, use "content-"
headers in entirity, "content-type: blah", "content-language: blah",
"Content-MD5: blah" or whatever.
document-format-description := content-header
-- http://www.parc.xerox.com/masinter