RE: SequenceNumber [was:minutes 21-Dec-2000 tr&p con-call]

["Burdett, David" <david.burdett@commerceone.com>]

Shimamura

I think that our thoughts are beginning to converge. I agree that making
sequence number unique within conversation id makes sense.

I have also read your paper, and think that we have two alternatives:
1. Your alternative where we have a separate messageOrderSemantics that
indicates that the sequence of arrival of messages within the conversation
MUST be preserved by a recipient.
2. Use the existence of the sequence number to imply that sequence must be
preserved. This would mean that the first message in a conversation would
have to have a sequence number and the omission of a sequence number later
would be an error. Similarly the presence of a sequence number when there
wasn't one on the first would also be an error.

I do think though that if we do have messageOrderSemantics.

I am also wondering if we need to worry about overflow if sequence number is
going to be unique with Conversation Id. For example, if sequence has a
maximum value of 99,999,999 then effectively a conversation with a 100
million messages would, I think, in practice never occur.

Thoughts?

David

-----Original Message-----
From: SHIMAMURA Masayoshi [mailto:shima.masa@jp.fujitsu.com]
Sent: Thursday, January 04, 2001 12:56 AM
To: Burdett, David
Cc: ebXML Transport (E-mail); IWASA Kazunori; Jacques Durand
Subject: Re: SequenceNumber [was:minutes 21-Dec-2000 tr&p con-call]


Mr. David Burdett, 

On Wed, 03 Jan 2001 12:05:59 -0800
"Burdett, David" <david.burdett@commerceone.com> wrote:
...
> This is not my recollection. In fact if you look at the DTD in version 0.8
> of the spec you will see that SequenceNumber need not be present in a
> Routing Header (see line 1268) which is defined as follows ...
> 
> <!ELEMENT RoutingHeader (SenderURI , ReceiverURI , ErrorURI , Timestamp ,
> SequenceNumber? )>
> 
> Making SequenceNumber mandatory is something that we did not agree to do.

The SequenceNumber is needed when DeliverySemantics is "OnceAndOnlyOnce".
So the DTD was defined as above, I think.

> Also the current version of the spec uses sequence number so that the
> recipient can detect duplicates. However, as Chris Ferris says is in his
> email, this doesn't always work. Some additional situations which cause
> problems are:
...
> However I can see how preserving the sequence could be useful and
important
> to some applications. So in the current 0.91 version of the spec, the
> definition of SequenceNumber is defined as being unique within
Conversation
> Id so that if you need to preserve message order then you can.

I agree to generation of SequenceNumber for each ConversationId. Thank
you for your suggestion. I hope you also add detailed description of
SequenceNumber and new attribute "messageOrderSemantics" of
ReliableMessagingInfo to the MS spec. I show my modification idea in
attached file.


Regards, 

--
SHIMAMURA Masayoshi <shima.masa@jp.fujitsu.com>
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