4.8.7.4 Sequence Number

Basic Definition | Description| | Example

Basic Definition

Property Name: SEQUENCE
Purpose: This property defines the revision sequence number of the calendar component within a sequence of revisions.
Value Type: integer
Property Parameters: Non-standard property parameters can be specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO" or "VJOURNAL" calendar component.

Description

When a calendar component is created, its sequence number is zero (US-ASCII decimal 48). It is monotonically incremented by the "Organizer's" CUA each time the "Organizer" makes a significant revision to the calendar component. When the "Organizer" makes changes to one of the following properties, the sequence number MUST be incremented:

. "DTSTART"

. "DTEND"

. "DUE"

. "RDATE"

. "RRULE"

. "EXDATE"

. "EXRULE"

. "STATUS"

In addition, changes made by the "Organizer" to other properties can also force the sequence number to be incremented. The "Organizer" CUA MUST increment the sequence number when ever it makes changes to properties in the calendar component that the "Organizer" deems will jeopardize the validity of the participation status of the "Attendees". For example, changing the location of a meeting from one locale to another distant locale could effectively impact the participation status of the "Attendees".

The "Organizer" includes this property in an iCalendar object that it sends to an "Attendee" to specify the current version of the calendar component.

The "Attendee" includes this property in an iCalendar object that it sends to the "Organizer" to specify the version of the calendar component that the "Attendee" is referring to.

A change to the sequence number is not the mechanism that an "Organizer" uses to request a response from the "Attendees". The "RSVP" parameter on the "ATTENDEE" property is used by the "Organizer" to indicate that a response from the "Attendees" is requested.

Format Definition

This property is defined by the following
notation:

  seq = "SEQUENCE" seqparam ":" integer CRLF
  ; Default is "0"

  seqparam   = *(";" xparam)

Example

The following is an example of this property for a calendar
component that was just created by the "Organizer".

  SEQUENCE:0

The following is an example of this property for a calendar component
that has been revised two different times by the "Organizer".

  SEQUENCE:2

iCalendar specification excerpts TOC