Re: Can we fix BYSETPOS?

[Eric Busboom <eric@xxxxxxxxxxxxxxxxxx>]

On Fri, 18 May 2001, Jonathan Lennox wrote:

> On Friday, May 18 2001, "Eric Busboom" wrote to "Jonathan Lennox, <Bruce_Kahn@xxxxxxxx>, <ietf-calendar@xxxxxxx>" saying:
>
> > BYSETPOS is problematic for a number of reasons, but there may be a way to
> > fix it so that CPL can use it.
>
> However, the concept "set of events specified by the rule" is terribly
> vague.

Right. How about this as proposed text, as an addition to 4.3.10,
Recurrence Rule:

---------------------------------------------------------------------------

  BYSETPOS operates on a set of events in one interval of the recurrence
  rule. For a WEEKLY RULE, the interval is one week, for a MONTHLY rule,
  one month, and for a YEARLY rule, one year. After the recurrence rule is
  expanded for one week, month or year, occurrences are selected from this
  set according to the positions in the set specified by the elements of
  BYSETPOS. BYSETPOS is applied to each successive week, month or yearly
  interval of the rule to generate the final occurrence set.

  BYSETPOS MUST NOT be used with SECONDLY, MINUTELY, HOURLY or DAILY
  rules. If any of  BYSECOND, BYMINUTE or BYHOUR rule parts appear in a
  rule, BYSETPOS MUST NOT appear.

---------------------------------------------------------------------------

The first paragraph clarifies how to use BYSETPOS, and the second limits
it's use to rules that generate no more than one occurrence per day, so an
implementation will never have to expand more than 366 occurrences per
interval.

Jonathan, will this work for CPL? Bruce, is this acceptable for iCalendar?

eric.