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Re: Proposed text on reliability in the web services architecture

From: Miles Sabin <miles@milessabin.com>
Date: Tue, 21 Jan 2003 19:58:16 +0000
To: www-ws-arch@w3.org
Message-Id: <200301211958.16944.miles@milessabin.com>

Assaf Arkin wrote,
> Let's say that the problem you describe goes away. The message is
> always successfully delivered to the application. However, the
> application try as it may cannot process it. So you're still at
> square one: you know it was delivered, but not that it was processed.
>
> That's the scope of RM. RM is about delivery not processing. When you
> start worrying about whether the message was processed or not you
> need to look at higher levels of coordination. The RM simply says
> that an ack means delivery.

Agreed, completely.

But the complication is: what counts as delivery? Does it mean delivery 
to the application? Or does it mean delivery to the last node that's 
participating in the RM protocol (the HTTP/SMTP server in my example)?

If you count the HTTP/SMTP server as part of the application, then these 
two coincide of course. Unfortunately there's a lot of scope for 
confusion about whether they are or not (ie. exactly what the 
boundaries of the application are), and consequently potential for 
ambiguity about what reliable delivery actually amounts to.

Ultimately, this is a problem without a solution ... reliable 
communication is an end to end property of the link between the 
ultimate applications at either end of the link, and if that can't be 
arranged then reliability along only part of the link doesn't really 
help.

But all I think that implies is that a sender ought to be able to insist 
on RM and a gateway receiver ought to be able to decline if it can't 
provide it onwards.

Cheers,


Miles
Received on Tuesday, 21 January 2003 14:58:48 GMT

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