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RE: Comments on Message Exchange Pattern: Single Request-Response document

From: Williams, Stuart <skw@hplb.hpl.hp.com>
Date: Tue, 4 Dec 2001 14:12:30 -0000
Message-ID: <5E13A1874524D411A876006008CD059F1927C5@0-mail-1.hpl.hp.com>
To: "'Eamon O'Tuathail'" <eamon.otuathail@clipcode.com>
Cc: xml-dist-app@w3.org
Hi Eamon,
Nice to be exchanging mail with you again.
-----Original Message-----
From: Eamon O'Tuathail [mailto:eamon.otuathail@clipcode.com]
Sent: 04 December 2001 12:54
To: xml-dist-app@w3.org
Subject: Comments on Message Exchange Pattern: Single Request-Response

I have two comments on the MEP SRR document. 
There is discussion at the end of the document (in the section "Transport
Binding Framework Assumptions" onwards) concerning the "environment", which
is defined as "a container for those properties that are not scoped on a
per-message or per message exchange basis". This could includes items such
as session keys and certificates that are needed for multiple  message
exchanges and could be expensive to acquire. Unfortunately none of this
discussion has reached into the main body of the MEP SRR document - and it
should be there, as it will substantially improve performance where multiple
message exchanges occur.  
[SKW] Much of the discussion that you reference should propagate into what
gets proposed for the WD and be presented ahead of the specific MEP and
binding descriptions. What we were signalling was our intent to draw on
these various pieces of material. The text that you refer to did appear
first in an original draft, but got in the way of getting to review the MEP
which was the piece of work in hand at the time, so it got move to the back.

The second point is that the processing model is very simplified - it
assumes the responding node will completely receive all the data in the
incoming message before even starting to process it. It is likely that all
efficient implementations will start processing each part of the message as
soon as it arrives. Some might not be able to do anything until the end of
the request has arrived, but some bindings can react without having received
the end of the incoming message. If the request message is somehow
incorrect, such bindings could send back a pre-emptive error, thus
preventing the sender having to transmit the rest of the (faulty) request
message. If the request msg is e.g. 1 MB (e.g. with photo attachments) and
the sender can be told quickly that there is something wrong with it, then
this prevents wasting bandwidth and speeds up the sender in sending the
subsequently correct message.  
[SKW] Good point. I don't think that's hard to fix - indeed I have a revised
FSM jotted down. I don't know if it will make it into the immediate next
draft that we produce. What I hope is that we can achieve some concensus on
tone and style... that this is :-) (or is not :-(  ) a good way to describe
a binding... like/dislike of formality. With concensus on direction we can
fix the detail in a subsequent WD. 
Eamon O'Tuathail 
Best regards
Received on Tuesday, 4 December 2001 09:20:48 UTC

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