iTip using PARTICIPANT only

Internet-Draft	iTip participants	October 2024
Douglass	Expires 17 April 2025	[Page]

Abstract

This specification defines updates to RFC5546 iTip which allow scheduling using the PARTICIPANT components specified in RFC9073.¶

New properties are also defined for use within the PARTICIPANT component.¶

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶

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This Internet-Draft will expire on 17 April 2025.¶

Copyright Notice

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

1. Acknowledgements

The authors would like to thank the members of the Calendaring and Scheduling Consortium (CalConnect) for contributing their ideas and support.¶

2. Introduction

This specification details how the PARTICIPANT component introduced in [RFC9073] may be used for scheduling in place of [RFC5545] ATTENDEE and ORGANIZER properties. Additionally, some properties are defined in this specification to be used within the PARTICIPANT component.¶

For all existing schedulable and publishable components, VEVENT, VTODO, VFREEBUSY, and VAVAILABILITY; the ORGANIZER and ATTENDEE properties MUST be supplied as appropriate. For new components such as VPOLL, defined elsewhere, only PARTICIPANT components MUST be used.¶

A participant object that takes part in group scheduling MUST have the following characteristics:¶

It MUST have a calendar address as defined in Section 6.4 of [RFC9073].¶
It must have one or more scheduling roles defined in PARTICIPANT-TYPE¶

Scheduling with PARTICIPANT components behaves exactly as with ATTENDEE and ORGANIZER properties. When iTip specifies the setting of ATTENDEE or ORGANIZER parameters then the appropriate PARTICIPANT property will be set.¶

3. Terms and definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].¶

The notation used in this memo to (re-)define iCalendar elements is the ABNF notation of [RFC5234] as used by [RFC5545]. Any syntax elements shown below that are not explicitly defined in this specification come from iCalendar [RFC5545].¶

Additionally, the following terms are used:¶

3.1. participant

Represents an agent that takes part in scheduling or publishing. A participant may be a human, for example an attendee, or a resource, for example a conference room.¶

3.2. publishable

A component which takes part in [RFC5546] publishing operations.¶

3.3. schedulable

A component which takes part in [RFC5546] scheduling operations.¶

4. iCalendar Extensions

4.1. New Property Parameters

4.1.1. Required

Parameter name: REQUIRED¶
Purpose: To specify whether the associated property is required in the current context.¶
Format Definition: This parameter is defined by the following notation:¶

requirededparam = "REQUIRED"  "=" ("TRUE" / "FALSE")
  ; Default is FALSE

Description: This parameter MAY be specified on REPLY-URL and, if the value is TRUE, indicates the organizer requires all replies to be made via the specified service rather than iTip replies.¶

4.1.2. Reply-URL

Property name: REPLY-URL¶
Purpose: This property may be used in scheduling messages to indicate additional reply methods, for example a web-service.¶
Value type: URI¶
Property Parameters: Non-standard, required or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in any schedulable component.¶
Description: When used in a scheduling message this property indicates additional or required services that can be used to reply. Typically, this would be a web service of some form.¶
Format Definition: This property is defined by the following notation:¶

reply-url = "REPLY-URL" reply-urlparams ":" uri CRLF

reply-urlparams = *(
                  (";" requiredparam) /
                  (";" other-param)
                  )

4.2. Redefined participation type

This specification redefines the PARTICIPANT-TYPE property allowing it to take multiple values and extending those values to align with [RFC8984] roles. There are also changes to the description to clarify its use defining the roles that participant takes.¶

Property name: PARTICIPANT-TYPE¶
Purpose: This property is equivalent to the [RFC5545] ATTENDEE ROLE parameter but includes more values to align with [RFC8984].¶
Value Type: The value type for this property is TEXT. The allowable values are defined below.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MUST be specified once within a "PARTICIPANT" component.¶
Description: This property defines the type of participation, that is the roles the participant takes.
¶

It includes the values defined in [RFC8984].¶

Note that the kind of participant, for example individual or group, is defined in the KIND property specified here.¶

Some of the roles are required for the participant to be a schedulable object. These are the roles that are shown below.¶
Format Definition: This property is defined by the following notation:¶

participanttype   = "PARTICIPANT-TYPE" partvalueparam ":"
                     partvalue
                     *("," partvalue) CRLF

partvalue    = ("OWNER"
               / "ATTENDEE"
               / "OPTIONAL"
               / "INFORMATIONAL"
               / "CHAIR"
               / "ACTIVE"
               / "INACTIVE"
               / "SPONSOR"
               / "CONTACT"
               / "BOOKING-CONTACT"
               / "EMERGENCY-CONTACT"
               / "PUBLICITY-CONTACT"
               / "PLANNER-CONTACT"
               / "PERFORMER"
               / "SPEAKER"
               / iana-token)     ; Other IANA-registered
                                 ; values

partvalueparam   = *(";" other-param)

The values have the same meaning as defined in [RFC8984] and [RFC9073].¶

Other roles defined here have no direct equivalent in [RFC5545]¶

To map [RFC5545] ATTENDEE ROLE values to PARTICIPANT-TYPE values use the following.¶

Table 1
RFC5545 ROLE	PARTICIPANT-TYPE
CHAIR¶	CHAIR¶
REQ-PARTICIPANT¶	ATTENDEE¶
OPT-PARTICIPANT¶	OPTIONAL¶
NON-PARTICIPANT¶	INFORMATIONAL¶

The following table shows those roles that MUST appear in the PARTICIPANT-TYPE for group-scheduling. Additionally, the mapping for PARTICIPANT-TYPE to [RFC5545] ATTENDEE and ORGANIZER values are shown.¶

Table 2
PARTICIPANT-TYPE	RFC5545 ROLE
OWNER¶	Create ORGANIZER¶
ATTENDEE¶	REQ-PARTICIPANT¶
OPTIONAL¶	OPT-PARTICIPANT¶
INFORMATIONAL¶	NON-PARTICIPANT¶
CHAIR¶	CHAIR¶
Subsequent values have no [RFC5545] equivalent¶
CONTACT¶
VOTER¶
ACTIVE¶
INACTIVE¶
SPONSOR¶
BOOKING-CONTACT¶
EMERGENCY-CONTACT¶
PUBLICITY-CONTACT¶
PLANNER-CONTACT¶
PERFORMER¶
SPEAKER¶

Examples

PARTICIPANT-TYPE=OWNER,"…" (HORIZONTAL ELLIPSIS, U+2026)"" (ZERO WIDTH SPACE, U+200B) equivalent to an ORGANIZER¶
PARTICIPANT-TYPE=ATTENDEE,"…" (HORIZONTAL ELLIPSIS, U+2026)"" (ZERO WIDTH SPACE, U+200B) equivalent to the ATTENDEE property¶

5. New Participant Properties for iTip

The following properties are defined to be used within PARTICIPANT during scheduling and take the place of ATTENDEE and ORGANIZER properties and parameters.¶

5.1. Kind

Property name: KIND¶
Purpose: This is what kind of entity this participant is, if known.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in a PARTICIPANT component.¶
Description: When used in a PARTICIPANT component this property indicates the kind of entity, individual, group etc.
¶

It takes the values shown below which are a redefinition of the CUTYPE parameter values defined in [RFC5545] and aligned with [RFC8984] .¶
Format Definition: This property is defined by the following notation:¶

kind = "KIND" kindparams ":"
                "INDIVIDUAL"   ; An individual
              / "GROUP"        ; A group of individuals
              / "RESOURCE"     ; A physical resource
              / "LOCATION"     ; A location resource e.g a room
              / iana-token CRLF

kindparams = *(";" other-param)

5.2. Participation-status

Property name: PARTICIPATION-STATUS¶
Purpose: This property is used in the PARTICIPANT component to indicate the participation status - if any.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in a PARTICIPANT component.¶
Description: When used in a PARTICIPANT component this property indicates what status, if any, the participant has.
¶

It takes the same values as the PARTSTAT parameter defined in [RFC5545].¶
Format Definition: This property is defined by the following notation:¶

participation-status = "PARTICIPATION-STATUS"
                       participation-statusparams ":"
              NEEDS-ACTION / ; No status
                    ; has yet been set by the participant.

              ACCEPTED / ; The invited
                    ; participant will participate.
              DECLINED / ; The invited
                    ; participant will not participate.
               TENTATIVE / ; The invited participant
                     ; may participate.
                DELEGATED / ; The invited participant
                     ; has delegated their attendance to
                     ; another participant, as specified
                      ; in the PARTICIPATION-DELEGATED-TO property.
                COMPLETED / ; The assigned task is
                     ; completed.
                IN-PROCESS / ; The assigned task is
                     ; being worked on.
                    iana-token ("," iana-token) CRLF

participation-statusparams = *(";" other-param)

5.3. Participation delegated from

Property name: PARTICIPATION-DELEGATED-FROM¶
Purpose: This property is used in the PARTICIPANT component to indicate who has delegated their participation to this participant.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in a PARTICIPANT component.¶
Description: This property specifies those calendar users that have delegated their participation in a group-scheduled component to the calendar user specified by the component.¶
Format Definition: This property is defined by the following notation:¶

participation-delfrom = "PARTICIPATION-DELEGATED-FROM"
                        participation-delfromparams ":"
              CAL-ADDRESS
              *("," CAL-ADDRESS)
              iana-token ("," iana-token) CRLF

participation-delfromparams = *(";" other-param)

5.4. Participation delegated to

Property name: PARTICIPATION-DELEGATED-TO¶
Purpose: To specify the calendar users to whom the calendar user specified by the component has delegated participation.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in a PARTICIPANT component.¶
Description: This property specifies those calendar users that have been delegated participation in a group-scheduled component by the calendar user specified by the component.¶
Format Definition: This property is defined by the following notation:¶

participation-delto = "PARTICIPATION-DELEGATED-TO"
                      participation-deltoparams ":"
              CAL-ADDRESS
              *("," CAL-ADDRESS)
              iana-token ("," iana-token) CRLF

participation-deltoparams = *(";" other-param)

5.5. Member of

Property name: MEMBER-OF¶
Purpose: To specify the group or list membership of the calendar user specified by the component.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in a PARTICIPANT component.¶
Description: This property identifies the groups or list membership for the calendar user specified by the component. The value is one or more calendar addresses.¶
Format Definition: This property is defined by the following notation:¶

member-of = "MEMBER-OF" member-ogparams ":"
              CAL-ADDRESS
              *("," CAL-ADDRESS)
              iana-token ("," iana-token) CRLF

memberofparams = *(";" other-param)

5.6. Lang

Property name: LANG¶
Purpose: This is the language tag, as defined in [RFC5646], that best describes the participant's preferred language, if known.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in any appropriate component.¶
Format Definition: This property is defined by the following notation:¶

lang = "LANG" langparams ":" TEXT CRLF

langparams = *(";" other-param)

5.7. Expect reply

Property name: EXPECT-REPLY¶
Purpose: If true, the organizer is expecting the participant to notify them of their participation status.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified once in the PARTICIPANT component.¶
Format Definition: This property is defined by the following notation:¶

expect-reply = "EXPECT-REPLY"
              expect-replyparams ":"
              ( "TRUE" / "FALSE") CRLF

expect-replyparams = *(";" other-param)

5.8. Scheduling-agent

Property name: SCHEDULING-AGENT¶
Purpose: This is who is responsible for sending scheduling messages with this calendar object to the participant.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified once in the PARTICIPANT component.¶
Format Definition: This property is defined by the following notation:¶

scheduling-agent = "SCHEDULING-AGENT"
              scheduling-agentparams ":"
              ( "SERVER" /
                "CLIENT" /
                "NONE") CRLF

scheduling-agentparams = *(";" other-param)

The value MUST be one of the following values, another value registered in the IANA "JSCalendar Enum Values" registry, or a vendor-specific value.¶

SERVER: The calendar server will send the scheduling messages.¶
CLIENT: The calendar client will send the scheduling messages.¶
NONE: No scheduling messages are to be sent to this participant.¶

5.9. Scheduling-force-send

Property name: SCHEDULING-FORCE-SEND¶
Purpose: A client may set the property on a participant to true to request that the server send a scheduling message to the participant when it would not normally do so (e.g., if no significant change is made the object or the scheduleAgent is set to client). The property MUST NOT be stored in the JSCalendar object on the server or appear in a scheduling message.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified once in the PARTICIPANT component.¶
Format Definition: This property is defined by the following notation:¶

scheduling-force-send = "SCHEDULING-FORCE-SEND"
              scheduling-force-sendparams ":"
              ( "TRUE" / "FALSE") CRLF

scheduling-force-sendparams = *(";" other-param)

5.10. Scheduling-status

Property name: SCHEDULING-STATUS¶
Purpose: This is a list of status codes, returned from the processing of the most recent scheduling message sent to this participant. The status codes MUST be valid statcode values as defined in the ABNF in Section 3.8.8.3 of [RFC5545].¶

Servers MUST only add or change this property when they send a scheduling message to the participant. Clients SHOULD NOT change or remove this property if it was provided by the server. Clients MAY add, change, or remove the property for participants where the client is handling the scheduling.This property MUST NOT be included in scheduling messages.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in any appropriate component.¶
Format Definition: This property is defined by the following notation:¶

scheduling-status = "SCHEDULING-STATUS"
            scheduling-statusparams ":" TEXT CRLF

scheduling-statusparams = *(";" other-param)

5.11. Scheduling-dtstamp

Property name: SCHEDULING-DTSTAMP¶
Purpose: This is the timestamp for the most recent response from this participant.¶

This is the updated property of the last response when using iTIP. It can be compared to the updated property in future responses to detect and discard older responses delivered out of order.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in any appropriate component.¶
Format Definition: This property is defined by the following notation:¶

scheduling-dtstamp = "SCHEDULING-DTSTAMP"
            scheduling-dtstampparams ":" DATE-TIME CRLF

scheduling-dtstampparams = *(";" other-param)

5.12. Invited-by

Property name: INVITED-BY¶
Purpose: This is the calendar address of the participant who added this participant to the entity, if known.¶
Property Parameters: Non-standard or iana parameters can be specified on this property.¶
Conformance: This property MAY be specified in any appropriate component.¶
Format Definition: This property is defined by the following notation:¶

invited-by = "INVITED-BY"
            invited-byparams ":" CAL-ADDRESS CRLF

invited-byparams = *(";" other-param)

6. Attendee parameters mapping

Table 3
Parameter	iCalendar PARTICIPANT
CN¶	NAME (defined in [RFC7986]¶
CUTYPE¶	KIND (defined here)¶
DELEGATED-FROM¶	PARTICIPATION-DELEGATED-FROM Section 5.3 ¶
DELEGATED-TO¶	PARTICIPATION-DELEGATED-TO (Defined here)¶
DIR¶	LINK [RFC9253]¶
LANGUAGE¶	LANG (defined here)¶
MEMBER¶	MEMBER-OF (defined here)¶
PARTSTAT¶	PARTICIPATION-STATUS (defined here)¶
ROLE¶	PARTICIPATION-TYPE (Updated here)¶
RSVP¶	EXPECT-REPLY (Defined here)¶
SENT-BY¶

Table 4
Property Parameter	Status	Reference
REQUIRED¶	Current¶	Section 4.1.1 ¶

8.2. Property Registrations

This document defines the following new iCalendar properties to be added to the registry defined in Section 8.2.3 of [RFC5545]:¶

Table 5
Property	Status	Reference
EXPECT-REPLY¶	Current¶	Section 5.7 ¶
INVITED-BY¶	Current¶	Section 5.12 ¶
KIND¶	Current¶	Section 5.1 ¶
LANG¶	Current¶	Section 5.6 ¶
MEMBER-OF¶	Current¶	Section 5.5 ¶
PARTICIPATION-DELEGATED-FROM¶	Current¶	Section 5.3 ¶
PARTICIPATION-DELEGATED-TO¶	Current¶	Section 5.4 ¶
PARTICIPATION-STATUS¶	Current¶	Section 5.2 ¶
REPLY-URL¶	Current¶	Section 4.1.2 ¶
SCHEDULING-AGENT¶	Current¶	Section 5.8 ¶
SCHEDULING-DTSTAMP¶	Current¶	Section 5.11 ¶
SCHEDULING-FORCE-SEND¶	Current¶	Section 5.9 ¶
SCHEDULING-STATUS¶	Current¶	Section 5.10 ¶

8.3. Updated Participant Type Registrations

This updates the participant types registry defined in Section 11.2.1 of [RFC9073]¶

Table 6
Participant Type	Status	Reference
OWNER¶	Current¶	RFC8984 Section 4.4.6 of [RFC8984]¶
ATTENDEE¶	Current¶	RFC8984 Section 4.4.6 of [RFC8984]¶
OPTIONAL¶	Current¶	RFC8984 Section 4.4.6 of [RFC8984]¶
INFORMATIONAL¶	Current¶	RFC8984 Section 4.4.6 of [RFC8984]¶
CHAIR¶	Current¶	RFC8984 Section 4.4.6 of [RFC8984]¶

9. Normative References

[RFC2119]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC5234]: Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 5234, RFC 5234, DOI 10.17487/RFC5234, January 2008, <https://www.rfc-editor.org/info/rfc5234>.
[RFC5545]: Desruisseaux, B., Ed., "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", RFC 5545, RFC 5545, DOI 10.17487/RFC5545, September 2009, <https://www.rfc-editor.org/info/rfc5545>.
[RFC5546]: Daboo, C., Ed., "iCalendar Transport-Independent Interoperability Protocol (iTIP)", RFC 5546, RFC 5546, DOI 10.17487/RFC5546, December 2009, <https://www.rfc-editor.org/info/rfc5546>.
[RFC5646]: Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying Languages", RFC 5646, RFC 5646, DOI 10.17487/RFC5646, September 2009, <https://www.rfc-editor.org/info/rfc5646>.
[RFC7986]: Daboo, C., "New Properties for iCalendar", RFC 7986, RFC 7986, DOI 10.17487/RFC7986, October 2016, <https://www.rfc-editor.org/info/rfc7986>.
[RFC8984]: Jenkins, N. and R. Stepanek, "JSCalendar: A JSON Representation of Calendar Data", RFC 8984, RFC 8984, DOI 10.17487/RFC8984, July 2021, <https://www.rfc-editor.org/info/rfc8984>.
[RFC9073]: Douglass, M., "Event Publishing Extensions to iCalendar", RFC 9073, RFC 9073, DOI 10.17487/RFC9073, August 2021, <https://www.rfc-editor.org/info/rfc9073>.
[RFC9253]: "", RFC 9253, RFC 9253, <https://www.rfc-editor.org/rfc/rfc9253>.

Author's Address

Michael Douglass

Email: mdouglass@bedework.com