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Initial formulation of intermediary semantics for MTOM

From: <noah_mendelsohn@us.ibm.com>
Date: Fri, 29 Aug 2003 18:14:42 -0400
To: xml-dist-app@w3.org
Message-ID: <OFCF033977.3EFCDA77-ON85256D91.006E4944@lotus.com>





I took an action item af the France f2f to formulate a proposal for
intermediary handling of MTOM.  This note is in fulfillment of that action.
What I've written here is the rough outline of a direction.  The proposal
is as follows.  All section numbers are with respect to the MTOM WD at [1]:

<current fromSection="Introduction">
The usage of the Abstract Transmission Optimization Feature is a hop-by-hop
contract between a SOAP node and the next SOAP node in the SOAP message
path, providing no normative convention for optimization of SOAP
transmission through intermediaries.
</current>
<proposed forSection="Introduction">
The usage of the Abstract Transmission Optimization Feature is a hop-by-hop
contract between a SOAP node and the next SOAP node in the SOAP message
path, providing no mandatory convention for optimization of SOAP
transmission through intermediaries.   The feature does provide optional
means by which binding implementations MAY choose to facilitate the
efficient passthrough of optimized data contained within headers or bodies
relayed by an intermediary.
</proposed>

<current fromSection="2.4.3 Transmitting a Message">
The usage of the Abstract Transmission Optimization Feature is a hop-by-hop
contract between a SOAP node and the next SOAP node in the SOAP message
path. Therefore, no specific rules exist for a SOAP intermediary
implementing the Abstract Transmission Optimization Feature.
</current>
<proposed  forSection="2.4.3 Transmitting a Message">
The usage of the Abstract Transmission Optimization Feature is a hop-by-hop
contract between a SOAP node and the next SOAP node in the SOAP message
path. Therefore, no changes or restrictions to the SOAP processing model
are introduced by this feature at an intermediary.  Section 2.4.4 details
the means by which certain optimizations can be performed by bindings at
intermediaries.
</proposed>

<proposed newSection="2.4.4 Binding Optimizations at Intermediaries">
As described in SOAP Part 1 Section 2.7 Relaying SOAP Messages, a SOAP
intermediary may be called upon to to relay intact certain headers, or to
reinsert headers identical to those received and removed for processing.
Furthermore, many intermediaries will relay unmodified the contents of the
SOAP body.   In all these cases, portions of the relayed message have
content identical to corresponding portions of the inbound message.

The Abstract Transmission Optimization Feature does not require any
particular correspondence between the optimization of the inbound message
and the outbound message, even when optimized portions of the inbound
message are relayed intact, or reinserted in identical form in the envelope
Infoset.  Nonetheless, the implementations of the receiving binding and the
binding used to transmit the relayed message MAY cooperate to provide
efficient relay.  For example, if the inbound and outbound binding use the
same representation for optimized binary, the implementations MAY cooperate
to pass the optimized form directly from the inbound to the outbound
binding.  The choice of whether to implement such cooperation, and if so
the means used, is at the discretion of the binding specification(s) and/or
the implementation of the bindings.

Note:  a consequence of these rules is that there are no invariant rules
for the degree to which optimizations are preserved as a message passes
through intermediaries.  Certain outbound bindings may be incapable of any
optimization, and will therefore transmit unoptimized forms in all cases.
Other bindings may be capable of optimization, but may or may not choose to
or succeed in optimizing the same portions (if any) that were optimized in
the inbound message.  Other bindings, perhaps under the direction of logic
provided in SOAP modules or perhaps as consequence of conventions embodied
in the bindings, may optimize portions of the message that were not
optimized inbound, or which were optimized using different techniques.
</proposed>

[1] http://www.w3.org/TR/soap12-mtom/
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Noah Mendelsohn                              Voice: 1-617-693-4036
IBM Corporation                                Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
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Received on Friday, 29 August 2003 18:13:41 GMT

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