[Ietf-calsify] What is the appropriate serialization for a recurring event with one event changed?

[Jeffrey Harris]

Hi Folks,

I've been working a bit with Oracle's CalDAV server and Apple's iCal,
and they have pretty different behaviors when serializing a recurring
event with a change to one event.

Lets take, for example, a daily event, starting Monday at 9AM, last
occurrence Friday at 9AM.  If I change Wednesday's event to 11AM, what
should the resulting stream look like?

iCal exports this as two VEVENTs, one has (omitting lots of other lines):

DTSTART;TZID=US/Pacific:20051003T090000
RRULE:FREQ=DAILY;COUNT=5

the other VEVENT has

RECURRENCE-ID:20051005T160000Z          #Wednesday at 9AM PDT (in UTC)
DTSTART;TZID=US/Pacific:20051005T110000 #Wednesday at 11AM PDT

Oracle's stream also has two VEVENTs:

DTSTART;TZID=US/Pacific:20051003T090000
RRULE:FREQ=DAILY;COUNT=5
EXDATE:20051005T160000Z                #Wednesday at 9AM PDT (in UTC)

the other VEVENT has

RECURRENCE-ID:20051005T180000Z         #Wednesday at *11AM* PDT (in UTC)
DTSTART;TZID=US/Pacific:20051005T110000

Is one of these more correct than the other?  Is an EXDATE appropriate
for the original time if an event's time has been moved?  What does it
mean for a RECURRENCE-ID to reference a time that isn't already in the
recurrence set?

Sincerely,
Jeffrey