Subject: Re: CAP and Timezones/Recurrence/Queries

From: [email-masked]
Date: Thu, 30 Sep 1999 13:35:15 -0400

Thorsten Laux wrote, in part:

>1. From the cap draft I can't seem to figure out, how queries can 
>specify whether they want recurrent events to be returned only once 
>(the start of the series) or once for every occurrence in the queried 
>time span. It hopefully is not the burden of the CUA to calculate all 
>recurrences from the base event!?

You would specify a WHERE clause either for the UID for the parent, to get 
the whole recurrence definition, the RECURRENCE-ID for a particular 
recurrence instance, to get an individual occurrence, the RECURRENCE-ID 
and RECTYPE (i.e., "THISANDBEFORE" or "THISANDAFTER"), to get a range of 
recurrences.

>2. How do I specify the timezone of a datetime in a query? I suppose 
>the CUA does not have to readjust its query time span into GMT? 
>Burdening the CUA with timezone calculations means calculating 
>recurrence rules which I don't think is a good idea for CUAs to be 
>forced to. In the same context wouldn't it be a good idea to have the 
>CUA identify its timezone to the CS and then let the CS do all 
>timezone conversions for the client? The CS has to be able to do the 
>conversions anyway since it has (as I suppose) to calculate recurrence 
>instances. Why not let it do all conversion work. Having to do this in 
>two places is error prone - especially given the vast reservoir of 
>recurrence rules. It is clear of course that the tzid would still have 
>to be transmitted since it indicates the timezone, the date is tied 
>to.

Yes, specifying the date/time in terms of UTC (NOTE: GMT is deprecated. We 
all use UTC as the absolute time format) is the way to go. The CAP server 
would need to adjust/translate into absolute time of UTC. But good 
question. This should be noted in the specification.
Actually, CUAs will have to be able to do time zone conversion for many UI 
displays of data anyway. If you have a date/time in "floating" time, you 
will have to display this in your UI in the local time zone of the CUA. In 
addition, the most common form for specification of iCalendar DTSTART and 
DTEND properties will be UTC based format of time. You only need a time 
zone when a recurring event is specified. So, the CUA will have to UTC to 
local time conversion all the time anyway.

---

From: Doug Royer <[email-masked]>
Date: Thu, 30 Sep 1999 11:54:05 -0700

[email-masked] wrote:
> You would specify a WHERE clause either for the UID for the parent, to
> get the whole recurrence definition, the RECURRENCE-ID for a
> particular recurrence instance, to get an individual occurrence, the
> RECURRENCE-ID and RECTYPE (i.e., "THISANDBEFORE" or "THISANDAFTER"),
> to get a range of recurrences.

This implies that the CUA already knows the UID of an event.
If the query is for a date-time range there does not seem
to be a way to say send me the 'raw' iCalendar data or
'expand' the recurrences for me.

Doug
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