Re: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement

[Doug Bunting <dougb62@yahoo.com>]

This is getting a bit confused and I apologise for adding to the confusion.

David, I believe you've agreed with me in general and then taken a stance
different than mine.  That's fine but I'll still attempt to clear up the
disparity.  One note: MSH-level errors allowed after an end-to-end
acknowledgment completely confuse any state machine at the sender (leaving
everything indeterminate until long after TimeToLive has expired), means
retries might be necessary after an acknowledgment and / or goes against our
requirement that manual intervention or an acknowledgment are the only ways
to end the reliable messaging cycle.

Martin, I would agree completely with your statements about acknowledgments
recognising placement of a message in the persistent store if and only if we
made it clear that store was our mechanism for transfers to the application
space.  The current specification doesn't recognise that and doesn't require
any use of the persistent store except with regard to reliable messaging and
duplicate detection.  We don't even say the persistent store is logically
part of both the application and the MSH implementation.

Back to the original issue: What event(s) MUST occur prior to the
TimeToLive?  Arvola is absolutely correct in saying the current "delivered
and processed" wording uses an event far too late.  That definition would
require some MSH control over application processing timelines.

David F. seems to be suggesting TimeToLive should be checked only upon
receipt of a message.  That definitely occurs prior to sending an
acknowledgment message but seems like an event immaterial to the sender.  An
infinite-length queue or even no connection at all between the receiving MSH
and To Party application would become a reasonable implementation.

I'd prefer a middle ground.  The message is logically received, validated,
placed in persistent storage, acknowledged, processed by the application and
(optionally) responded to at a business level.  Use of the "placed in
persistent storage" event would be fine.  With Martin's interpretation of
"placed in persistent storage" as being semantically identical to "passed to
the application", it gets even better but I think we can avoid requiring
that being explicit in our specification.

thanx,
    doug

----- Original Message -----
From: "Martin W Sachs" <mwsachs@us.ibm.com>
To: "Burdett, David" <david.burdett@commerceone.com>
Cc: <ebxml-msg@lists.oasis-open.org>
Sent: Tuesday, 11 December 2001 15:31
Subject: RE: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement

It seems to me that we have all at least implicitly agreed that depositing
a message in the persistent store constitutes delivery to the application
(not unlike the postal service delivering a letter to a post office box).
That's the event that should be governed by time to live.

See my previous posting.

Regards,
Marty

****************************************************************************
*********

Martin W. Sachs
IBM T. J. Watson Research Center
P. O. B. 704
Yorktown Hts, NY 10598
914-784-7287;  IBM tie line 863-7287
Notes address:  Martin W Sachs/Watson/IBM
Internet address:  mwsachs @ us.ibm.com
****************************************************************************
*********



"Burdett, David" <david.burdett@commerceone.com> on 12/11/2001 06:17:24 PM

To:    ebxml-msg@lists.oasis-open.org
cc:
Subject:    RE: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement

I agree with Doug

The original intent behind TimeToLive is that it should indicate the time
by
which the message should be delivered to the application. Consider the use
case where the To Party MSH stores messages which, at the end of the day,
they forward in batch to an application. If we make the semantics mean that
the message will be processed, then, as Doug says, you can't send back the
acknowledgement until the message has been passed to the app.

I think it is completely valid to:
1. Send a delivery receipt to indicate that the message has been received
by
the To Party MSH
2. Later send an error message to indicate the the To Party MSH could not
deliver the message to the App before TimeToLive expired.

A delivery receipt is just that a receipt for **delivery** it is not an
indication that the message has been processed. That can only be provided
by
the application.

David

-----Original Message-----
From: Doug Bunting [mailto:dougb62@yahoo.com]
Sent: Tuesday, December 11, 2001 11:15 AM
To: ebxml-msg@lists.oasis-open.org
Subject: Re: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement

Hmmm, I remember no such decision and think it isn't a particularly useful
way to define TTL.  The sender couldn't care less when a receiver MSH gets
a
message, they care only about the application at the To Party.

As you comment, the underlying issue is (again) acknowledgments and their
semantics.  I completely agree an acknowledgment message MUST be the last
message an MSH could initiate with reference to a received message.  (Yes,
applications are free to respond to any message whenever they please -- I'm
talking only about MSH signals.)  In particular, error messages (such as
"TTL expired") MUST NOT be sent after an acknowledgment message has been
sent.  According to my understanding of TTL, this would mean an MSH
shouldn't send an acknowledgment until it has informed the application.

whatever,
    doug

----- Original Message -----
From: "David Fischer" <david@drummondgroup.com>
To: "Doug Bunting" <dougb62@yahoo.com>; <ebxml-msg@lists.oasis-open.org>
Sent: Tuesday, 11 December 2001 10:43
Subject: RE: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement


No, Arvola is right.

We decided a message could be delivered from the MSH to the Application
AFTER
TTL.  TTL is the time it must be delivered to the To Party MSH.  If this is
not
true, then the receiver could just hold any message he didn't like until
after
TTL and then discard, regardless of any Acknowledgments.  The sending of an
Acknowledgment constitutes a commitment by the MSH to deliver to the
Application
(what the Application does is undefined).

Regards,

David.

-----Original Message-----
From: Doug Bunting [mailto:dougb62@yahoo.com]
Sent: Tuesday, December 11, 2001 11:47 AM
To: ebxml-msg@lists.oasis-open.org
Subject: Re: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement

Arvola,

I disagree; the wording is fine as it is.

If the example you've described occurs, the To Party MSH is not operating
correctly.  The TimeToLive value is intended to be the time by which
(end-to-end, application-to-application, whatever you want to call it)
delivery must be complete.  That may mean the To Party MSH discards a
message after it has been persisted in some storage (but not delivered to
its application).

Going further, your previous recommendation made sense though the example
was also slightly incorrect.  In that example, a message found in
persistent
store after crash recovery might (MUST) be discarded due to an expired
TimeToLive value.  Of course, we can't say anything about how long it might
take an application to process a message...

thanx,
    doug

----- Original Message -----
From: "Arvola Chan" <arvola@tibco.com>
To: "David Fischer" <david@drummondgroup.com>;
<ebxml-msg@lists.oasis-open.org>
Sent: Monday, 10 December 2001 17:44
Subject: Re: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement

David:

The first paragraph in section 3.1.6.4 in the version 1.091 draft now
reads:

"If the TimeToLive element is present, it MUST be used to indicate the
time,
expressed in UTC, by which a message should be delivered to the To Party.
It
must conform to an XML Schema dateTime."

I think the phrase "To Party" should be replaced with "To Party MSH". The
To
Party MSH will check the incoming message to determine if its TimeToLive
has
expired. It may have to make a persistent copy of the message before
attempting to deliver it to the To Party. A crash may happen after the
message has been persisted but prior to its being delivered to the To
Party.
Therefore, it is entirely possible that the To Party only receives the
message after TimeToLive has passed.

Regards,
-Arvola

-----Original Message-----
From: David Fischer <david@drummondgroup.com>
To: Arvola Chan <arvola@tibco.com>; ebxml-msg@lists.oasis-open.org
<ebxml-msg@lists.oasis-open.org>
Date: Sunday, December 09, 2001 8:47 AM
Subject: RE: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement

>Yes, I will remove "and processed by".
>
>David.
>
>-----Original Message-----
>From: Arvola Chan [mailto:arvola@tibco.com]
>Sent: Friday, December 07, 2001 5:49 PM
>To: ebxml-msg@lists.oasis-open.org
>Subject: [ebxml-msg] Section 3.1.6.4 TimeToLiveElement
>
>This first paragraph in this section states:
>
>"The TimeToLive element indicates the time by which a message should be
>delivered to and processed by the To Party."
>
>I don't think the above statement is correct. The message must be received
>by the To Party MSH prior to its TimeToLive. Once it has been persisted by
>the To Party MSH, it can be delivered to the To Party. If a crash occurs
>after the message has been persisted but before it can be handed over to
the
>To Party, it is possible that it may be processed by the To Party (on
crash
>recovery) even after TimeToLive has expired.
>
>-Arvola
>
>
>
>
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