2.2.103 [RFC5546] Section 2.1.5 Message Sequencing

V0239:

The specification states that the primary key for referencing a particular iCalendar component is the UID property value. To reference an instance of a recurring component, the primary key is composed of the UID and the RECURRENCE-ID properties.

Microsoft Office Outlook 2007, Microsoft Outlook 2010, Microsoft Outlook 2013, Microsoft Outlook 2016, Microsoft Outlook 2019

Outlook can output iTIP data with just a UID property, and it can also output iTIP data with both a UID and RECURRENCE-ID.

On import, Outlook uses the UID and RECURRENCE-ID properties to property correlate a meeting request/response/cancellation/counter-proposal with a Calendar object.

C0025:

The specification uses the term UID in rules 2 – 4 in [RFC5546], but does not mention the RECURRENCE-ID.

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

It is assumed that the use of UID in rules 2 – 4 is referring to the combination of the UID and RECURRENCE-ID property as described in rule 1.

V0240:

The specification states that the secondary key for referencing a component is the SEQUENCE property value. For components where the UID is the same, the component with the highest numerical value for the SEQUENCE property obsoletes all other revisions of the component with lower values.

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

Outlook can export multiple versions of a meeting request and multiple responses to a meeting request. On import, Outlook uses the SEQUENCE property to determine which revision is the latest.

V0241:

The specification states that attendees send REPLY messages to the organizer. For replies where the UID property value is the same, the value of the SEQUENCE property indicates the revision of the component to which the attendee is replying. The reply with the highest numerical value for the SEQUENCE property obsoletes all other replies with lower values.

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

When generating a REPLY iCalendar object, Outlook uses the same SEQUENCE number as the REQUEST iCalendar that the user is responding to. On import, Outlook uses the SEQUENCE property to determine which revision is the latest.

V0242:

The specification states that in situations where the UID and SEQUENCE properties match, the DTSTAMP property is used as the tie-breaker. The component with the latest DTSTAMP overrides all others.

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

Outlook always exports a DTSTAMP property that can be used to break ties in the SEQUENCE number. On import, Outlook uses the DTSTAMP property to break ties in the SEQUENCE number.

V0243:

The specification states that for each ATTENDEE property of a component, calendar user agents must persist the SEQUENCE and DTSTAMP property values associated with the attendee's response.

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

Outlook persists the DTSTAMP property associated with the attendee's response. However, the SEQUENCE number is only indirectly persisted. All responses that do not match the SEQUENCE number of the meeting are ignored, and all responses are invalidated when the SEQUENCE number is incremented on the meeting.