Subject: RFC 2445 & RECURRNECE-ID

From: [email-masked]
Date: Thu, 31 Aug 2000 16:55:08 -0400

Time for a change of focus, back to RFC 2445.  In trying to work on 
recurrences better I noticed a slight oversight in the current RFC 2445 
text WRT RECURRENCE-ID and multiple recurrences on the same day.  The ABNF 
for RECURRENCE-ID is:

     recurid    = "RECURRENCE-ID" ridparam ":" ridval CRLF

     ridparam   = *(

                ; the following are optional,
                ; but MUST NOT occur more than once

                (";" "VALUE" "=" ("DATE-TIME" / "DATE)) /
                (";" tzidparam) / (";" rangeparam) /
[Snip]
                )

     ridval     = date-time / date
     ;Value MUST match value type

There is also text in the description that says:

   If the value of the "DTSTART" property is a DATE type value, then the
   value MUST be the calendar date for the recurrence instance.

However we did overlook a possibility, that the entry repeats more than 
once on the same day (ie: BYHOUR=9,10) and the CUA sends:

        DTSTART:20000901T090000
        RECURRENCE-ID;VALUE=DATE:20000904

Just which instance is this RECURRENCE-ID for (there is no RANGE 
parameter)??  I think we should tighten up RFC 2445 to to address the 
multiple instance on a single day case when VALUE=DATE is specified.  In 
particular I suggest we expressly preclude VALUE=DATE (and date only 
values) when are > 1 instances on that date.  Comments??

Bruce
===========================================================================
Bruce Kahn                                INet: [email-masked]
Iris Associates                          Phone: 978.392.5335
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