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Subject: Re: [ebxml-msg] Reliable Messaging question

Dick et al,

I agree that ErrorList@highestSeverity="Error" is a great way to end the retry loop in other specifications.  I also agree this is common practise and something worth including in our specification.

Unfortunately, the current document is very explicit in 7.5.4 and elsewhere.  It makes it clear communication errors result in additional retries and that Retries or receiving an Acknowledgment are the only ways to end the retry loop.  See bullets starting at 1716 for example.  We use MUST in many of those comments.

My issue 125 addressed an apparent conflict between these explicit rules and some of the error semantics.  I'm not sure why I originally made the comment on line 1352 (section; lines 1312-1313 (section would have been more appropriate.  In any case, says the ErrorList stops everything but the rest of the document says only Acknowledgment stops retries.

To Michael's point about deferring a correction in this area 'til a later version, I'd say the current conflicting MUST requirements need to be fixed now.  Changing the document to explicitly include ErrorList@highestSeverity="Error" in the exit points for the retry loop is a fine solution.  I didn't like a need to bundle an Acknowledgment with such an ErrorList but didn't see a simpler way to correct the problem.


Dick Brooks wrote:

 >David's comment makes sense.  I can't think of a reson why I would respond
>in the same message with an Acknowledgment element AND an ErrorList
>element .  I would only ack a message after all MSH level related validation
>has passed. 
 I concur, ErrorList and Acknowledgement are mutually exclusive in the OTA and Energy ebXML specs I've worked with, here are excerpts from the two specs:Energy spec:"NOTE: The existence of an Acknowledgement element in a Response indicates that a Request was processed successfully. The existence of an ErrorList element in a Response indicates that a Request has failed.When a request message contains deliverySemantics of “OnceAndOnlyOnce” its corresponding response message MUST contain either an <Acknowledgement> or <ErrorList> element."OTA spec:"The existence of an Acknowledgement element in a Response indicates that a Request message was successfully received. The existence of an ErrorList in a Response indicates that a Request has failed. "

Dick Brooks
Systrends, Inc
7855 South River Parkway, Suite 111
Tempe, Arizona 85284
Web: www.systrends.com <http://www.systrends.com>

-----Original Message-----
From: Michael Wang [mailto:mwang@tibco.com]
Sent: Thursday, February 14, 2002 2:57 AM
To: ebxml-msg@lists.oasis-open.org
Subject: Re: [ebxml-msg] Reliable Messaging question
If the position is to let the retry kick in then are we saying the sender MSH
should "ignore" the ErrorList message and just let the retry to complete?
Then report back to application of the N retries it did and all the Errors it
got back?

David's comment makes sense.  I can't think of a reson why I would respond
in the same message with an Acknowledgment element AND an ErrorList
element .  I would only ack a message after all MSH level related validation
has passed.

May be too late for 2.0 but I would say this introduces unnecessary complexity.
Should probabaly be looked into post 2.0.


Doug Bunting wrote:


Almost every error may be transient.  Further, our documentation gives no "out" for the sending MSH other than exceeding the Retries parameter or receiving an appropriate Acknowledgment.  Adding the ErrorList element to that list of outs would be very different from 1.0 and would involve multiple changes to our document.  That's in spite of the a receiving MSH already being able to send ErrorList and Acknowledgment together.

125 was an editorial issue because the other parts of our specification were clear what could stop retries.  The section referenced in issue 125 muddied things.  Let's not turn this into a new technical issue.


David Fischer wrote:

Why would an MSH continue sending retries after receiving an ErrorList for that MessageId?  Section 6.5.7 indicates that when a message cannot be delivered then a DFN must be returned.  You are right though, it doesn't actually say not to send any more retries. I'm a little confused...  If an Acknowledgment is present with an ErrorList, does that mean the MSH does or doesn't send a DFN to the application?  I suppose if the message got far enough so that the receiving MSH could actually generate an Acknowledgment then that would constitute delivery for the purposes of RM? I think this would be OK -- send an ErrorList and an Acknowledgment together.I'm still not clear why the sending MSH would continue to send retries if it got an ErrorList (containing the appropriate RefToMessageId) from the receiving MSH but without an Acknowledgment?Regards,David FischerDrummond Group.
-----Original Message-----
From: Doug Bunting [mailto:dougb62@yahoo.com]
Sent: Wednesday, February 13, 2002 7:23 PM
To: ebxml-msg@lists.oasis-open.org
Subject: Re: [ebxml-msg] Reliable Messaging question

I believe this is captured in issue 125.  In David's response [1], he indicated an ErrorList could end retries but that interpretation is not borne out by our current documentation and seems incorrect.  I would suggest we stick with the current retry semantics and end retries only upon receipt of an Acknowledgment or exhaustion of allowable retries.  If a MSH receiving a message in error chooses to respond with an Acknowledgment bundled together with an ErrorList, fine.

I also agree this option (combining Acknowledgment with ErrorList) isn't well described.  Improving that description was the intent of issue 125.


[1] http://lists.oasis-open.org/archives/ebxml-msg/200202/msg00006.html (specifically, the XML file attached and unhelpfully inlined by the OASIS site)

Arvola Chan wrote:

 Section 7.5.2 in Draft version 2.0 describes Receiving Message Behavior under the ebXML Reliable Messaging Protocol. It does not mention anything about error handling. Suppose the received message is erroneous (e.g., some elements in the message are inconsistent with the CPA), the receiver is obligated to return an Error message. It is not clear to me if an Acknowledgment MUST also be included in the Error message. Does the Error message serve as an implicit Acknowledgement? Will the sender keep retrying until it gets back an Acknowledgment (i.e., as long as the number of allowable retries have not been exhausted)? Thanks,-Arvola

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