- From: Cutler, Roger (RogerCutler) <RogerCutler@chevrontexaco.com>
- Date: Thu, 23 Oct 2003 09:31:50 -0500
- To: "He, Hao" <Hao.He@thomson.com.au>, www-ws-arch@w3.org
The explanation is fine, but isn't the definition a little odd? It seems to me that the highest level of certainty that sender and receiver have the SAME understanding of the status of message delivery is when both know it CAN'T HAPPEN AT ALL ... EVER! I realize that there are problems making a succinct definition because of the impossibility of actually guaranteeing delivery in a distributed system (stated loosely), but can't we do better than this? You probably considered this and rejected it for some good reason, but what is wrong with the more direct: "Message reliability is the degree of certainty that a message will be delivered". Or, perhaps, "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". It seems to me that the definition should have something to do with what you really want, not a secondary matter that you think might result in what you want but actually might have some other result. That wasn't stated very well, I know, but perhaps you get the drift. -----Original Message----- From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org] On Behalf Of He, Hao Sent: Thursday, October 23, 2003 6:44 AM To: 'www-ws-arch@w3.org ' Subject: Message reliability Based on the discussion of last f2f: http://www.w3.org/2002/ws/arch/3/09/2003-09-25-ws-arch.htm Reliable messaging is now called message reliability. We still need to write text on other aspects of reliability. Hao 2.3.1.13 Message reliability 2.3.1.13.1 Definition Message reliability is the degree of certainty to which both the sender and the recipient have the same understanding of the status of message delivery. ... 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 Thursday, 23 October 2003 10:32:15 UTC