Created: [Apr 6, 2004]

Defines a SEQUENCE iCalendar component property.

    4.8.7.4 Sequence Number

       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