Re: [calsify] «For a given pair of "UID" and "SEQUENCE" property values, the "RECURRENCE-ID" value for a recurrence instance is fixed.»

[Neil Jenkins <[e-mail]>]

On Tue, 4 Jan 2022, at 5:20 AM, Dilyan Palauzov wrote:
> https://datatracker.ietf.org/doc/html/rfc5545#page-113 says for  
> RECURRENCE-ID: «For a given pair of "UID" and "SEQUENCE" property  
> values, the "RECURRENCE-ID" value for a recurrence instance is fixed.»

Given the text above, I'm pretty sure that "for a recurrence instance" means a specific instance of a recurring event. This seems a bit tautological to me, as the recurrence id by definition is unique for a specific recurrence instance of a particualr UID, regardless of SEQUENCE. I'm not sure what the authors really intended to say there, but my reading is this statement doesn't really mean anything.

> Consider this iCalendar object:
> 
> BEGIN:VCALENDAR
> VERSION:2.0
> BEGIN:VEVENT
> UID:123
> SEQUENCE:1
> DTSTART:20211201T221500Z
> DTEND:20211201T223000Z
> SUMMARY:ANNA NANA ANAN NANA
> RRULE:FREQ=DAILY;COUNT=14
> END:VEVENT
> BEGIN:VEVENT
> UID:123
> SEQUENCE:2
> DTSTART:20211208T221500Z
> DTEND:20211208T223000Z
> SUMMARY:Exception
> RECURRENCE-ID:20211208T221500Z
> END:VEVENT
> BEGIN:VEVENT
> UID:123
> SEQUENCE:2
> DTSTART:20211213T103000Z
> DTEND:20211213T230000Z
> SUMMARY:Another exception
> RECURRENCE-ID:20211213T221500Z
> END:EVENT
> END:VCALENDAR
> 
> As can be seen, the last two VEVENTs have the same UID and SEQUENCE,  
> but different RECURRENCE-ID.  So for a given UID and SEQUENCE, the  
> RECURRENCE-ID is not fixed in that file.
> 
> Is the VCALENDAR valid or invalid?

So based on the above, my view is that this is valid.

—Neil