iCalendar and iMIP Introduction

iCalendar Compenents:

• VCALENDAR - MIME type text/calendar
• VEVENT component
• VTODO component
• VFREEBUSY component
• VJOURNAL component
• VTIMEZONE sub-component
• VALARM sub-component
• Can all the components be simplified to VEVENT??
• Semantics: what is the meaning of a VCALENDAR? What is the relationship between VEVENTs in the same VCALENDAR?

iCalendar references:

• RFC 2445 - iCalendar format
• Viewing components in UML
• Apple iCal white paper
• XML RDF for iCalendar
• Tim Berners-Lee reviews iCalendar

iCalendar properties and parameters:

• General outline of data model
  • Example: "ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:MAILTO:jsmith@host.com"
  • "ATTENDEE" is the property
  • "RSVP" and "ROLE" are parameters, "TRUE" and "REQ-PARTICIPANT" are parameter values
  • semi-colons separate parameters
  • first colon indicates beginning of value
  • value is "MAILTO:jsmith@host.com"
• SUMMARY on VEVENT, VTODO and VJOURNAL
• UID
• DTSTART
  • "TZID=US-Eastern" - example of specifying timezone by label
• DTEND and DURATION
• VALARM:TRIGGER -- limited values
• VALARM:ACTION -- limited values -- e.g. no value for "Send instant message"
• Value type of URI -- does this automatically cause derefererencing?
• Delegation:
  • Example: ATTENDEE;DELEGATED-TO="mailto:a@y.com";DELEGATED-FROM="mailto:b@y.com":c@y.com
  • Who is attending the meeting, a or c?

Recurrance and recurrance rules

• RECURRANCE-ID
• RRULE property
• FREQ parameter: value = SECONDLY | MINUTELY | HOURLY | DAILY | MONTHLY | YEARLY
• INTERVAL parameter: value = integer
• More parameters: BYSECOND | BYMINUTE | BYHOUR | BYDAY | BYMONTHDAY | BYYEARDAY | BYWEEKNO | BYMONTH | BYSETPOS | WKST
• End-recurrance parameters: COUNT or UNTIL
• Example:
  • FREQ=MINUTELY;INTERVAL=5;BYDAY=MO,WE
  • I'm not sure this even makes sense but I think it's "every five minutes on Mondays and Wednesdays"
• Example:
  • RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1
  • See bottom of this page to find out what that rule is...
• Example:
  • FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;BYMINUTE=30
  • First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to arrive at "every other year". Then, "BYMONTH=1" would be applied to arrive at "every January, every other year". Then, "BYDAY=SU" would be applied to arrive at "every Sunday in January, every other year". Then, "BYHOUR=8,9" would be applied to arrive at "every Sunday in January at 8 AM and 9 AM, every other year". Then, "BYMINUTE=30" would be applied to arrive at "every Sunday in January at 8:30 AM and 9:30 AM, every other year". Then, lacking information from RRULE, the second is derived from DTSTART, to end up in "every Sunday in January at 8:30:00 AM and 9:30:00 AM, every other year"
• Now Timezones can be much more complicated

Use cases for iCalendar (without iTIP/iMIP)

• Save entire calendar as a single file
  • Issues: single VCALENDAR file not good as a native storage format as a single file. However a local store can adapt iCalendar into several files or a database.
• Export/import
• Import process can combine imported events with existing events
• Publish calendar as single file - Apple's iCal
• Issues: single VCALENDAR file even less appropriate for calendar sharing among multiple authors.

xCalendar and RDF-iCal

• XML has taken over
• Not obvious how to translate iCalendar custom data to XML
• Even more difficult to translate XML extensions back to iCalendar
• Data model inconsistencies:
  • iCalendar has calendars, components, subcomponents, properties, parameters.
  • XML has documents, elements and attributes.
• Data typing inconsistencies:
  • Meaning of "integer"
  • Meaning of "timestamp"
• Difficult transition

iTIP: wrapping iCalendar

Overview

• RFC 2446
• METHOD
  • PUBLISH -- FYI
  • REQUEST -- Invitation
  • REPLY -- used by attendees to indicate status (will or will not attend)
  • ADD -- used by organizer to add a recurrance?
  • CANCEL -- used by organizer to cancel by UID
  • REFRESH -- used by attendees to ask for an update by UID
  • COUNTER -- used by attendees to suggest an alternate time/place
  • DECLINECOUNTER -- used by organizer to decline
• SEQUENCE

Use cases for iTIP:

• need a way to transmit them somehow... can't use iTIP alone
• XMPP transport for iTIP been discussed

Issues

• Not really worked out how to use in multi-author or multi-client situations

iMIP: wrapping iTIP wrapping iCalendar

• RFC 2447
• Message header
• Use cases: invitations only -- specialized
• Issues: email is not a good transport
  • Recipient is a person with multiple mail agents
  • What happens when your email agent doesn't do calendaring?
  • What happens when email is received by multiple mail agents who all try to accept meeting?
  • How do attendees see updated meeting status?
  • No way to learn recipient's capabilities (e.g. support for xCalendar, custom properties)

what did that rule mean? "RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1" means "Last weekday of the month"

-- LisaDusseault - 05 Oct 2004