Subject: [calsify] Call for action: fail RRULE parsing on unknown parameters

From: Gregory Yakushev <[email-masked]>
Date: Mon, 17 Jun 2013 11:55:14 +0200

This letter is an outcome of CalConnect round table discussion.

Currently some calendaring libraries and services silently ignore RRULE
parameters they don't understand. Such behavior contradicts the spec (
http://tools.ietf.org/html/rfc5545#section-3.3.10), and prevents any
extension to the RRULE behavior.

We want to add a new parameter to the RRULE, which modifies set of
instances produced by it. If a client or service silently ignores the new
parameter, it will produce incorrect set of instances causing data
inconsistency. The best such a client can do is to reject RRULE it doesn't
understand, and do not produce any set of instances for it.

Bug will be filed shortly for ical4j, fixing which should also fix all
dependent services (including our Google Calendar). If you are aware of
other implementations of iCalendar parsing, please post here so we can
cover them too.

Best Regards
Grisha
Google Inc.