Subject: Re: SCHRANGE

From: [email-masked]
Date: Tue, 31 Aug 1999 20:44:48 GMT

Greg:
Doug's proposal of having DTSTART have a list of values is not supported 
in the current iCalendar spec, section 4.8.2.4 "Date/Time Start". It can 
only take a single DATE-TIME or DATE value. This approach is problematic 
for interoperability with exiting iCalendar-based products. As such, it 
should be tossed in favor of an approach that provide backwards 
compatibility with iCalendar products.
It would seem that what ever approach we take, we would want for this 
iCalendar object to be parsable by existing iCalendar-based products. It 
was this rationale that led me to believe that a different property, other 
than DTSTART, should be used to specify the scheduling range for the 
event. For example, you can specify a possible DTSTART and possible DTEND 
but also add the flexible DTSTART-RANGE and flexible DTEND-RANGE 
properties to convey the possible range of start and end times. With this 
approach, an existing iCalendar-based product would properly parse the 
event information and be able to skip over the two new properties it did 
not understand. But, if we change DTSTART and DTEND to take on a PERIOD 
value it would not be parsable by existing products.
There are many ways to design this support. We should choice the approach 
that provides the strongest backwards compatibility with existing 
iCalendar products.
For example:
START:VEVENT
...
SUMMARY:Two day conference on tentative calendar events
DTSTART;VALUE=DATE:19990830
DTEND;VALUE=DATE:199900831
DTSTART-RANGE;VALUE=DATE-PERIOD**:19990830/19990903
DTSTART-RANGE;VALUE=DATE-PERIOD**:19990831/19990904
COMMENT:** Note: DATE-PERIOD is assumed to be a new value type that
 specifies a date period based on the ISO 8601 time period format.
...
END:VEVENT
-- Frank