Alternate serializations of XML?

I haven't tracked the list closely, so apologies if this is a FAQ.

It appears that we're likely to see at least one alternate serialization
of the XML infoset in the not-too-distant future. For example, there is
active work (summarized at [1])  in ITU-T and ISO to define a few
different mappings of it to XML.

Without debating how useful these encodings will be, I wonder how they'll
be rationalized with the media type system. I see three options:

a) Define a single media type (e.g., "application/xml-asn1") to identify
all such formats (which seems to fall in the same pit as text/xml and
application/xml).

b) For every format, define a media type for each encoding (e.g.,
"application/svg+xml" and "application/svg+asn1"). However, this requires
multiple registrations, and may be bad for interoperability if encodings
aren't registered. Doesn't seem scalable.

c) Describe it as an encoding that's orthoganal to the media type; e.g.,
much as a MIME content-transfer-encoding or HTTP content-coding.
Format-specific encodings are unusual, to say the least, but I can't find
anything that prohibits them.

Are there other options?


1. http://asn1.elibel.tm.fr/xml/

--
Mark Nottingham