Calendaring standards developments

Yesterday saw the end of the IETF Calendaring and Scheduling Working Group.

What this means, in effect, is an end to work on the Calendaring Access Protocol (CAP). CAP was supposed to be the standard for client-server interaction on shared calendar servers. My (admittedly non-developer) perspective is that over the years of discussion, CAP grew to be so large and inclusive that nobody was going to bother to implement it in any interoperable way.

It will be interesting to see if the problems with CAP were due to the inherently complex nature of calendaring and scheduling, or whether there are some lighter-weight approaches that will solve most, if not all, of the problems of interoperable Internet calendaring.

Activity on calendaring standards has now morphed into two separate discussions:

- A proposal for a new client-server protocol being dubbed CalDAV, based on the WebDAV protocol. Lisa Dusseault from OSAF has an initial draft for this protocol, and there is an IETF mailing list for it here. CalDAV standardizes the type of approach taken by Apple's iCal and Mozilla Calendar (now dubbed Sunbird), using a WebDAV server to store calendar events. OSAF has (unsurprisingly) stated that they are planning to support CalDAV in Chandler.

- A new effort to revise the base iCalendar data format (rfc 2445), based on real-world experiences gained from actual products trying to achieve some level of interoperability. There is an active IETF mailing list for this topic - lately the discussion there has centered around whether or not alarms on events should be supported in the data exchange and to what extent access control should be supported in the format (which is necessary to support features like preserving confidentiality in specific calendar items when exchanging data).

Keep watching this channel for further developments :)

Update - 09 September 2004

Doug Royer, the author of the CAP protocol writes:

No - It is not the end of CAP. It is the first revision of CAP.

CAP will be released as EXPERIMENTAL until the next revision. This has been under consideration for months and all of the authors and primary IETF chairs and area directors are in agreement.