Subject: Re iCal-Basic - draft 00

From: Doug Royer <[email-masked]>
Date: Sat, 08 Jan 2005 10:42:41 -0700

I know that there was a large debate on having both DURATION
and DTEND years ago that resulted in 2445. Now that we are trying
to simplify down to  the basics. Can we pick just one?

     DTSTART and optionally DURATION (no  DTEND in spec)

or

     DTSTART and optionally DTEND. (no DURATION in spec)

This is an data format for exchanging calendar information, it has
nothing to do with how any implementation stores the data. Is the
reason that both existed because the WG could not decide? Or
was there another reason?

-- 

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From: "Shannon Clark" <[email-masked]>
Date: Sat, 8 Jan 2005 17:24:40 -0600

Well while they seem similar they can, in some cases, encode something
different.

Specifically - A DTSTART and DTEND without duration can, in the case of
certain timezones and daylight savings time changes result in difficult
to determine duration. (i.e. a DTSTART of midnight, a DTEND of 3:00am -
is that a 3 hour, 2 hour or 4 hour event? Could be any of them depending
on the date and timezone.

Likewise in the same case a DTSTART and DURATION can result is different
endtimes dependant on certain dates.

More specifically I think that it was/is an issue of different
calendaring programs implementing events in each way - some with start
and end times, other with start and duration (I don't know of any that
use endtime and duration but technically that could also be used at
least in theory).

All three at the same time is broken by many time changes for daylight
savings.

It also comes down to what is considered immoveable about the event. Is
it the DURATION? Or the End time. When the events are either repeating
or being negotiated the two systems can result in somewhat different
behaviors and assumptions. There may also be some usecases where it is
important to switch from one mode to another.

i.e. "The Meeting HAS TO END BY 5:00pm" - so the DTEND has to be
considered fixed, if the start time changes, the meeting is shorter -
not lengthened automatically.

Alternatively "The test is 4 hours long" - i.e. no matter when the start
time is rescheduled for, the end time has to be 4 hours later.

I think the key for the standard is that all of these cases can
reasonablely be handled, accommodated and dealt with. This may actually
also require some concept of "fixed vs. negotiable" but that is an issue
for another day.

Shannon 

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]] On Behalf Of Doug Royer
Sent: Saturday, January 08, 2005 11:43 AM
To: [email-masked]
Subject: Re iCal-Basic - draft 00

or

--

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From: [email-masked]
Date: Sat, 08 Jan 2005 21:12:08 -0500

In the most common use cases (which we can assume iCal-Basic is aiming 
for), an event is either an "appointment", which is a personal event that 
starts at a certain time and lasts for a period of time; or it's a 
"meeting" which is a multi-user event that starts at a certain time and 
lasts for a period of time.

I therefore would recommend DTSTART and DURATION in the iCal-Basic spec. 
Various implementations can, of course, choose to also store the DTEND 
information, but should use DURATION when exchanging information with other 
implementations.

Tim

>was there another reason?

Tim Hare
Interested Bystander, Non-Inc.