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Re: Issue 455 closed: Representation header and SOAP processing model

From: <noah_mendelsohn@us.ibm.com>
Date: Thu, 18 Mar 2004 18:25:06 -0500
To: Anish Karmarkar <Anish.Karmarkar@oracle.com>
Cc: Jean-Jacques Moreau <jean-jacques.moreau@crf.canon.fr>, xml-dist-app@w3.org
Message-ID: <OF7C875F68.4482AE66-ON85256E5B.0080A473@lotus.com>





(moved to distApp for discussion)

Anish Karamarkar writes (on the XMLP Comments list):

> I would imagine that a node that has knowledge of the
> downstream nodes and their capabilities/roles would be
> an active intermediary and in that case all bets are
> off. Comments?

I was thinking about it a bit differently.  The rules for forwarding
intermediaries say [1]:

"Forwarding SOAP intermediaries MUST also obey the specification for the
SOAP forwarding features being used. The specification for each such a
feature MUST describe the required semantics, including the rules
describing how the forwarded message is constructed. Such rules MAY
describe placement of inserted or reinserted SOAP header blocks. Inserted
SOAP header blocks might be indistinguishable from one or more of the
header blocks removed by the intermediary. Processing is defined here in
terms of re-inserting header blocks (rather than leaving them in place) to
emphasize the need to process them at each SOAP node along the SOAP message
path."

So, the header (feature/module) specification must tell us whether a
forwarding intermediary re-inserts a header that has been processed.  In
this case, I am proposing that our particular specification for the
representation header defer to specifications that may be written to
describe particular roles.  So, for example, the SOAP Rec. itself specifies
the special roles next, etc.

My proposal is that I should be able, for example, to say that the node:
http://example.org/noahsMachine is in fact a role that is by definition to
be assumed only by my machine.  Of course, SOAP processing software in
general has no particular knowledge of this, but nothing prevents
particular nodes from choosing to be aware of this rule.  I am suggesting
that we allow for the >possibility< that such roles would be invented, and
that their specifications would suggest that it would be unnecessary to
relay the content further.  I think this is consistent with forwarding
intermeds. as defined in SOAP.

There is one loophole with which one does have to be careful: there is no
mustUnderstand for role names.  So, while I think the above is possible, it
should only be attempted in situations in which the sender has high
confidence that the targeted receiver will do the right thing, or that
downstream nodes will be tolerant if it doesn't (e.g. dsigs won't break if
the content is not removed.)

Which reminds me:  we should probably also say that all these rules for
Representation are to be observed unless overridden by the specification
for some other header that was understood and processed at the node.  This
will allow us to later invent headers that change the rules for retaining
representation (unlikely, but no reason not to leave the door open I
think.)

Noah

[1] http://www.w3.org/TR/soap12-part1/#forwardinter

--------------------------------------
Noah Mendelsohn
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------
Received on Thursday, 18 March 2004 18:26:29 GMT

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