Representation header

This message is intended to start discussion of a "Representation" 
header as part of the MTOM work.

PASWA proposed one such header:
   http://www.gotdotnet.com/team/jeffsch/paswa/paswa61.html#_Toc36994434

In a nutshell, the intent here is to enable SOAP messages to carry 
representations of Web resources (i.e., what you get back when you 
dereference a URI) in SOAP headers, to accommodate the "portable cache" 
use case (UC2).

Because Web representations are often conveyed as MIME or MIME-like 
messages, one issue that should be considered is what MIME or MIME-like 
mechanisms (e.g., transfer-encoding, content-encoding, 
content-transfer-encoding, content-language and other headers) should 
be accommodated in the Representation header, and how should the be 
serialised?

I'd expect that the kinds of headers you might see associated with a 
Representation could be anything you'd see on a MIME Multipart message 
part, or any header classed as "instance-header", "variant-header" or 
"entity-header" according to Jeff Mogul's "Clarifying the Fundamentals 
of HTTP"[1] in Table 2.

My suggestion would be that Representation needs to:
   1) be extensible in the same way that MIME or HTTP headers are; i.e., 
you can add arbitrary headers
   2) needs to consider a mapping to and from the syntax of MIME and 
HTTP headers (e.g., header folding, etc.); possibly just 
canonicalization.


1. http://www2002.org/CDROM/refereed/444/


--
Mark Nottingham   Principal Technologist
Office of the CTO   BEA Systems