Subject: [Ietf-calsify] iTIP: persisting SEQUENCE number

From: caleb at everyone.net (Caleb Richardson)
Date: Mon Oct 1 18:31:46 2007

Your theory seems to be consistent with Frank Dawson's view:

http://www.imc.org/ietf-calendar/archive1/msg03546.html

> Correct. The sequence number applies to any modifications
> for the whole event definition. A change to an initial event
> definition to, say add (via the ADD method) an occurrence,
> would monotonically increment the sequence number. Effectively,
> the sequence number represents the revision sequence for the
> whole event definition.
> 
> Note: The UID applies to the whole occurrence set (or whole event) also.

Whether or not to bump the sequence number on CANCEL is a separate issue, I believe that it was discussed at great length on either this list or the old ietf-calendar list, with the resolution that it is ultimately the decision of the organizer. Both techniques make sense depending on the circumstances.

Caleb Richardson
Software Engineer
Everyone.net
[email-masked]

--- [email-masked] wrote:

Hi folks,
In trying to come up with some clarifying text for the SEQUENCE property I 
ran into the following situation:

1) Create a recurring meeting, Monday-Friday for five instances only.
2) Invite an attendee: this will send a REQUEST with SEQUENCE:0.
3) Override the Wednesday meeting by moving forward an hour. This will send 
a REQUEST for that instance only with SEQUENCE:1.
4) Delete the Thursday instance. This will send a CANCEL for that instance 
only.

Question: what should the SEQUENCE number be for the CANCEL?

There are two possibilities depending on how you read things:

1) SEQUENCE:1 - this is one more than SEQUENCE:0 which was the last 
sequence number used for the instance being cancelled.
2) SEQUENCE:2 - this is one more than the largest SEQUENCE sent in prior 
messages.

The problem with this ambiguity is that two clients could interpret this 
differently, so that one sends out SEQUENCE:1 as per the first 
interpretation, but the second is expecting SEQUENCE:2 as per the second 
interpretation, so it discards the message as being out of date.

My feeling is that when the ORGANIZER has to increment the SEQUENCE number 
they MUST use a value that is higher than the largest SEQUENCE previously 
sent for the entire recurrence set.

Does that make sense? If not, why not?

-- 
Cyrus Daboo

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