Subject: Re: Another recurrence ambiguity

From: [email-masked]
Date: Mon, 27 Nov 2000 12:09:27 -0500

Damon asked:
>If you have a weekly RRULE what do you do if it has BYDAY=2TU ?

This is yet another of those "ya cant get there from here" illogical 
RRULEs that some of us raised a while ago.  Im not sure what change Eric 
has made in the recurrence text but I know there was a proposal on the 
list to have text added that said in some form: "A recurrence rule MUST 
NOT have components that generate 'disjoint' subsets of one another.  For 
example: BYMONTH=1, BYYEARDAY=155."  The intent is to restrict what BYxxx 
may be used given the FREQ and INTERVAL values (and prior BYxxx values).

Bruce
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Bruce Kahn                                INet: [email-masked]
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From: John Stracke <[email-masked]>
Date: Mon, 27 Nov 2000 13:02:33 -0500

[email-masked] wrote:

> there was a proposal on the list to have text added that said
> in some form: "A recurrence rule MUST NOT have components that
> generate 'disjoint' subsets of one another.  For example:
> BYMONTH=1, BYYEARDAY=155."  The intent is to restrict what
> BYxxx may be used given the FREQ and INTERVAL values (and prior
> BYxxx values).

Of course, if you do get an event with an inconsistent RRULE,
then the meaning is obvious: the set of recurrences is empty
(it's the intersection of two disjoint sets), so the event never
repeats.  So the VCALENDAR is clear and unambiguous.  It just
happens to be useless.  :-)

--
/==============================================================\
|John Stracke    | http://www.ecal.com |My opinions are my own.|
|Chief Scientist |=============================================|
|eCal Corp.      |Excuse me. I've been dead lately & my brain  |
[email-masked]|isn't working too well. --Miles Vorkosigan   |
\==============================================================/

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From: Federico Mena Quintero <[email-masked]>
Date: Mon, 27 Nov 2000 13:12:48 -0600

> happens to be useless.  :-)

Which is another thing that begs the question:  has anyone ever even
considered how to make a good user interface to specify all of
iCalendar's recurrence rules?

In the Evolution calendar we support only very simple rules, similar
to the ones in the Palm Pilot's calendar program.  These seem to be
what people use most of the time; we can load and display iCalendar
exotica but not edit them.

  Federico