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RE: Message reliability

From: Cutler, Roger (RogerCutler) <RogerCutler@chevrontexaco.com>
Date: Fri, 24 Oct 2003 11:48:18 -0500
Message-ID: <7FCB5A9F010AAE419A79A54B44F3718E026EFE97@bocnte2k3.boc.chevrontexaco.net>
To: michael.mahan@nokia.com, Hao.He@thomson.com.au, www-ws-arch@w3.org
Cc: Mike.Champion@SoftwareAG-USA.com

Are you aware of the objections I had to the definition that strikes
what you want striken?  How do you answer that?

-----Original Message-----
From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org] On
Behalf Of michael.mahan@nokia.com
Sent: Friday, October 24, 2003 10:59 AM
To: Hao.He@thomson.com.au; www-ws-arch@w3.org
Cc: Mike.Champion@SoftwareAG-USA.com
Subject: RE: Message reliability



Two issues:

The definition states only that the messaging parties involved are 
suitably informed and have the same understanding of delivery status. 
The explanation then states that the goal is to reduce error 
frequency. It seems that this should be stricken - unless it is in 
scope for reliable messaging to address compensating actions. (I 
don't know if that is true or not, but the definition doesn't say 
it).

Also, the explanation discusses overall system reliability which 
for me is tried to repeatable results. The explanation then claims 
that performance is enhanced at both the message and system level 
when message reliability is applied. The way I measure performance 
is by speed and latency metrics. In this dimension, reliable messaging 
does not enhance performance.

Mike


>-----Original Message-----
>From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
>Behalf Of ext He, Hao
>Sent: October 23, 2003 06:14 PM
>To: 'www-ws-arch@w3.org '
>Cc: 'Champion, Mike'
>Subject: RE: Message reliability
>
>
>It was agreed to accept Roger's definition in today's
>discussion, so the
>text has been modified to reflect the decision. 
>
>Editors of the architecture document, please incorporate the
>text into the
>document.
>
>Hao
>
>
> 2.3.1.13 Message reliability
>2.3.1.13.1 Definition
>Message reliability is the degree of certainty that a message will be 
>delivered and that sender and recipient will both have the same 
>understanding of the delivery status.
>
>... skip ...
>
>2.3.1.13.3 Explanation
>
>
>The goal of message reliability is to both reduce the error
>frequency for
>messaging and to provide sufficient information about the status of a
>message delivery. Such information enables a participating 
>agent to make
>a compensating decision when errors or less than desired results occur.
>High level correlation such "two-phase commit" is needed if 
>more than two
>agents are involved. Note that in a distributed system, it is 
>theoretically
>not possible to guarantee correct notification of delivery; however, in
>practice, simple techniques can greatly increase the overall confidence
>in the message delivery.
>
>It is important to note that a guarantee of the delivery of messages 
>alone does not improve the overall reliability of a Web service due
>to the "end-to-end argument."[1]  It may, however, improve the 
>performance
>of
>messaging, and therefore, the overall performance of a Web service.
>
>Message reliability may be realized with a combination of
>message receipt
>acknowledgement and correlation. In the event that a message 
>has not been 
>properly received and acted upon, the sender may attempt a 
>resend, or some
>other compensating action at the application level.
>
>[1]http://www.reed.com/Papers/EndtoEnd.html
>
Received on Friday, 24 October 2003 12:49:20 GMT

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