Subject: To repeat or not...

From: [email-masked]
Date: Mon, 19 Jun 2000 12:27:31 -0400

That is kinda my question.  In doing an indepth analysis of the recurrence 
grammar and related topics I cannot find any info / specs on what the best 
course of action is for a CUA when encountering a bad or malformed 
recurrence rule (RRULE or EXRULE).  There are a couple paths to follow:

1: Flag the offender as bad; ignore it and attempt to roll out the rest of 
the recurrence set.
2: Flag the offender as bad; ignore any recurrence rule based data as 
suspect and only use repeat dates 
3: Flag the offender as bad; ignore all recurrences (dates or grammar 
based).

#1 is the most forgiving but it can also result responses to incomplete 
repeat sets.  Its not clear how the Organziers CUA would be able to 
indicate this to the Organzier.  The Attendees CUA can put up some 
indicator and attempt to clearly tell the user that the entry being viewed 
is not necessarily what the Organizer sent them.

#2 is a balance between #1 and #3.  However it has the byproduct of 
producing entries that may or may NOT be in the Organizers intended repeat 
set (ie: the EXRULE is malformed).  This would only be useful if there 
were both dates and recurrence rules on the entry.  For the cases where no 
dates were given, this collapses into a single entry case (with errors.)

#3 is the closest to my normal KISS mantra but Im not too keen on tossing 
out all of the recurrence set for what could be either technical (ie: 
COUNT=0;UNTIL=...) error or a logical one (ie: BYMONTH=1;BYWEEKNO=32).  It 
feels a bit too heavy handed.

So Im polling the WG to see what other folks think the proper CUA 
behaviour should be when dealing with bad recurrence rules (or exception 
rules).  Im also curious as to what other implementors have done (I know 
some of you are out there)...  There are probably other possible paths to 
follow but Im under caffinated and have a big headache so Im not 
cogitating too  hard just now.

Bruce
===========================================================================
Bruce Kahn                                INet: [email-masked]
Iris Associates                          Phone: 978.392.5335
Westford, MA, USA 01886                    FAX: and nothing but the FAX...
Standard disclaimers apply, even where prohibited by law...

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From: Colin DuPlantis <[email-masked]>
Date: Mon, 19 Jun 2000 10:16:16 -0700

[email-masked] wrote:
> 
> 1: Flag the offender as bad; ignore it and attempt to roll out the
> rest of the recurrence set.

My favorite is #3.  It seems to me that the worst result possible is
unexpected results.  If a malformed RRULE or EXRULE results in the whole
lot being thrown out, it may result in Organize frustration.  On the
other hand, if some, but not all, recurrences were accepted, it may
result in an inconsistent state, which would confuse everybody.

Besides, I guess my sympathy leans toward the implementer, and #3 would
probably be the easiest and most straightforward to implement.

- C

-- 
Colin DuPlantis
Synchronization and Protocols Development Manager
Critical Path, Inc.
185 Berry Street, Suite 4700
San Francisco, CA 94107
Direct: 415.659.3558
Fax:    415.659.0006
http://www.cp.net

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From: John Stracke <[email-masked]>
Date: Mon, 19 Jun 2000 13:32:12 -0400

[email-masked] wrote:

> That is kinda my question.  In doing an indepth analysis of the
> recurrence grammar and related topics I cannot find any info /
> specs on what the best course of action is for a CUA when
> encountering a bad or malformed recurrence rule (RRULE or
> EXRULE).

I think it depends on the context.  If the error is in an
incoming iTIP message, the receiver should send back an error to
the sender, since they're the only person who can correct the
mistake.  You don't want your CUA guessing what they mean,
because it's almost certain it'll guess wrong at least some of
the time, and then you'll miss meetings, or show up to meetings
that aren't happening.

If you're in a CAP context, and the error is in an iCalendar
stored on your CS...geez.  Offer the user a form to ask the
Organizer to resend?

--
/===============================================================\
|John Stracke    | http://www.ecal.com |My opinions are my own. |
|Chief Scientist |==============================================|
|eCal Corp.      |Reality is what refuses to go away when I stop|
[email-masked]|believing in it.                              |
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