I don't recall what the status of the "OPES over SOAP" discussions
is, but FYI:
http://www.ietf.org/internet-drafts/draft-nielsen-dime-00.txt
Think of DIME as MIME Multipart with byte-counting. It can be used
with SOAP envelopes containing handling instructions as the first
attachment, and a chunked payload (e.g., HTTP message) following;
this is well-suited for OPES use cases.
It's anticipated that a layering of DIME upon raw TCP will be
defined, so that one can use SOAP w/DIME as a means of constructing a
protocol without any other underlying application protocol.
This isn't taking into account the argument that it isn't necessary
to have a callout protocol, which is what I think Mark is saying (and
I've had an inclination to agree with for some time)...
Cheers,
--
Mark Nottingham, Research Scientist
Akamai Technologies (San Mateo, CA USA)