Then in that case the proper method is to say
Content-Type: application/xml; xml-type=iotp
As I've said repeatedly, this is fine in academic theory but fails miserably in
the real world.
And if there exist engines that do not underatand parameters, then they
are broken (but at least they will default to treating it as generic xml).
Unfortunately, the majority of MIME dispatchers fall into this category. So
much so that they cannot be ignored. You can complain about their brokenness
all you want but it isn't accomplishing anything.
And given the choice between having the ability to dispatch to specific
XML handlers without the ability to fall back on generic XML handling and
having only generic XML handling without the ability to dispatch to a
specific handler, the former is obviously better.
But the whole idea of a "token", as used in MIME up till now, is that it
is an atomic object - software is never required to do more than match it
against its list of recognised tokens.
Actually, a fair number of implementations already allow wildcards in MIME
types. So in practice this already works in some cases.
Ned