iCalendar Format Extensions for JSCalendar
draft-ietf-calext-icalendar-jscalendar-extensions-01

calext                                                       R. Stepanek
Internet-Draft                                                  Fastmail
Intended status: Standards Track                             3 June 2025
Expires: 5 December 2025

               iCalendar Format Extensions for JSCalendar
          draft-ietf-calext-icalendar-jscalendar-extensions-01

Abstract

   This document defines a set of new elements for iCalendar and extends
   the use of existing ones.  Their main purpose is to extend the
   semantics of iCalendar with elements defined in JSCalendar, but the
   new definitions also aim to be useful within just the iCalendar
   format.  This document updates RFC 5545 ("Internet Calendaring and
   Scheduling Core Object Specification (iCalendar)").

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 5 December 2025.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   2
     1.2.  ABNF Notations  . . . . . . . . . . . . . . . . . . . . .   3
   2.  Updated Properties  . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  GEO Property  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Updated Components  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  VLOCATION component . . . . . . . . . . . . . . . . . . .   4
   4.  New Properties  . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  COORDINATES Property  . . . . . . . . . . . . . . . . . .   4
     4.2.  SHOW-WITHOUT-TIME Property  . . . . . . . . . . . . . . .   5
     4.3.  URI Property  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  New Components  . . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  VCONFERENCE Component . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The JSCalendar [I-D.stepanek-jscalendarbis] format aims to be an
   alternative to the iCalendar [RFC5545] format for representation of
   calendaring data.  As such, it introduces new semantics that are not
   covered in the current definition of iCalendar and its various
   extensions.  Converting calendaring data between the two formats is
   defined in [I-D.ietf-calext-jscalendar-icalendar] with the goal of
   not losing any semantics during conversion.  To achieve this, this
   document defines new elements iCalendar and extends existing
   definitions.  Doing so, it follows the recommendations for
   introducing new iCalendar elements as specified in Section 3 of
   [RFC7986].

1.1.  Notational Conventions

   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 BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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1.2.  ABNF Notations

   The ABNF definitions in this document use the notations of [RFC5234].
   ABNF rules not defined in this document are defined in either
   [RFC5234] (such as the ABNF for CRLF, WSP, DQUOTE, VCHAR, ALPHA, and
   DIGIT) or [RFC5545].

2.  Updated Properties

2.1.  GEO Property

   This specification deprecates the "GEO" property and introduces the
   "COORDINATES" (Section 4.1) property to replace it.  Implementations
   SHOULD NOT use the "GEO" property to represent spatial coordinates.
   Instead, they SHOULD specify the "COORDINATES" property in a
   "VLOCATION" component [RFC9073] (Section 7.2).  They MAY additionally
   specify a "GEO" property in a "VEVENT" or "VTODO" component, in which
   case its "DERIVED" parameter [RFC9073] (Section 5.3) MUST have value
   "TRUE".

   The remainder of this section documents the rationale for deprecating
   the "GEO" property:

   The "GEO" property definition dates back to 1998, a time at which
   multiple internet protocols and data formats incorporated spatial
   coordinates in slightly different formats, making interoperability
   difficult.  This got addressed in 2010 in [RFC5870], which introduced
   a Uniform Resource Identifier (URI) for geographic locations.  The
   'geo' URI scheme not only improves interoperability but also allows
   for richer information than the "GEO" property value, e.g. it
   supports specifying the location altitude and the spatial uncertainty
   of the coordinates.

   Alternatively to deprecating, this specification could have updated
   the "GEO" property to allow its property value type to be URI.  This
   turned out to not interoperate, as implementations tended to reject
   such iCalendar data as invalid.  This was regardless if the "GEO"
   property was specified in a "VEVENT" component, or if it was
   specified in iCalendar components that were unsupported by the
   implementation (e.g. an implementation that was unaware of the
   "VLOCATION" component still rejected the "GEO" property with value
   type URI in that component as invalid).  Introducing a new property
   turned out to better interoperate with such systems.

3.  Updated Components

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3.1.  VLOCATION component

   This document updates the definition of the "VLOCATION" component.
   It allows to specify the newly defined "COORDINATES" property
   (Section 4.1) at most once in a "VLOCATION" component.  It appends
   the following to the "Format Definition" of the "VLOCATION"
   component, defined in Section 7.2 of [RFC9073]:

   locprop /= *(
               ;
               ; The following is OPTIONAL
               ; but MUST NOT occur more than once.
               ;
               coord
               ;
               )

   The "coord" ABNF is defined in Section 4.1.

4.  New Properties

4.1.  COORDINATES Property

   Property Name:  COORDINATES

   Purpose:  To represent a geographic location using the protocol-
      independent, extensible "geo" URI scheme.

   Value Type:  URI -- no default

   Property Parameters:  IANA and non-standard parameters MAY be
      specified on this property.

   Conformance:  This property can be specified in a "VLOCATION"
      calendar component.

   Description:  This property represents spatial (geographic)
      coordinates.  In contrast to the the "GEO" property, this property
      allows to represent not only latitude and longitude but also
      altitude of a location.  In addition, it supports to indicate the
      uncertainty of the coordinates, is interoperable with other
      internet standards making use of spatial information, and is
      extensible, such as for use with other coordinate reference
      systems.  The property value MUST a URI in the "geo" URI scheme,
      as defined in [RFC5870] and updates.

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   Format Definition:
      coord       = "COORDINATES" coordparam ":" uri CRLF

      coordparam  = *(
                     ;
                     ; The following is REQUIRED,
                     ; but MUST NOT occur more than once.
                     ;
                     (";" "VALUE" "=" "URI") /
                     ;
                     ; The following is OPTIONAL,
                     ; and MAY occur more than once.
                     ;
                     (";" other-param)
                     ;
                     )

   Example:  The following is an example of this property:

      COORDINATES;VALUE=URI:geo:48.198634,16.371648;crs=wgs84;u=40

4.2.  SHOW-WITHOUT-TIME Property

   Property Name:  SHOW-WITHOUT-TIME

   Purpose:  To indicate that the exact time span is not important when
      displaying this calendar object.

   Value Type:  BOOLEAN -- no default

   Property Parameters:  IANA and non-standard parameters can be
      specified on this property.

   Conformance:  This property can be specified in a "VEVENT" or "VTODO"
      calendar component.

   Description:  This indicates that the exact time span is not
      important to display when rendering this calendar object.  An
      example of this is an event that occurs over a full or almost full
      day, but in contrast to a DATE value is limited to a specific time
      zone or business hours.  While the time component is important for
      free-busy calculations and checking for scheduling clashes,
      calendars may choose to display it as an all-day event, or display
      the object separately to other objects to enhance the user's view
      of their schedule.

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      This property only is for presentation purposes, it does not have
      any impact on the temporal span or value type of a calendar
      object.

      This property MAY be specified on VEVENT components where the
      DTSTART property is of type DATE-TIME, or in VTODO components
      where either the DTSTART or DUE property is specified and has type
      DATE-TIME.  In all other cases it MUST NOT be set.  If this
      property is set, its property value MUST be "TRUE", e.g. it MUST
      be omitted rather than having value "FALSE".

      Implementations that are unaware of the "SHOW-WITHOUT-TIME"
      property might inadvertently preserve this property when changing
      a calendar object's temporal type from DATE-TIME to DATE.
      Implementations SHOULD therefore ignore rather than reject the
      incorrectly specified SHOW-WITHOUT-TIME property.  They MUST NOT
      preserve the ill-specified property in the calendaring data.

   Format Definition:
      showwt      = "SHOW-WITHOUT-TIME" showwtparam ":" "TRUE" CRLF

      showwtparam = *(
                     ;
                     ; The following is REQUIRED,
                     ; but MUST NOT occur more than once.
                     ;
                     (";" "VALUE" "=" "BOOLEAN") /
                     ;
                     ; The following is OPTIONAL,
                     ; and MAY occur more than once.
                     ;
                     (";" other-param)
                     ;
                     )

   Example:
      SHOW-WITHOUT-TIME;VALUE=BOOLEAN:TRUE

4.3.  URI Property

   Property Name:  URI

   Purpose:  To associate a Uniform Resource Identifier (URI) with a
      calendar component.

   Value Type:  URI -- no default

   Property Parameters:  The "LANGUAGE" parameter MUST NOT be specified

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      on this property.  Other IANA and non-standard parameters can be
      specified on this property.

   Conformance:  This property can be specified in a "VCONFERENCE"
      calendar component.

   Description:  This property associates a Uniform Resource Identifier
      [RFC3986] with a calendar component.  In contrast to the "UID"
      property, which defines its values to be of type TEXT, this
      property requires its value to be a syntactically valid URI.  In
      contrast to the "URL" property, this property neither provides a
      dynamic rendition of the associated calendar component, nor does
      it _locate_ a resource - it only identifies the calendar
      component.

      The semantics and purpose of this identifier MUST be defined for
      each calendar component containing the "URI" property.  This
      document defines the semantics of the "URI" property for the
      "VCONFERENCE" component.  Similarly, future iCalendar extensions
      might consider using the "URI" property in cases where associating
      calendaring data by use of the "UID" and "RELATED-TO" properties
      is not possible.

   Format Definition:
      uriprop     = "URI" uriparam ":" uri CRLF

      uriparam = *(
                  ;
                  ; The following is REQUIRED,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" "URI") /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:
      URI;VALUE=URI:urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6

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5.  New Components

5.1.  VCONFERENCE Component

   Component Name:  VCONFERENCE

   Purpose:  This component provides information about a virtual
      conference in addition to what is provided in the CONFERENCE
      property [RFC7986] (Section 5.11).

   Conformance:  This component can be specified in any component that
      allows to specify the "CONFERENCE" property.  It MAY occur
      multiple times, unless the "CONFERENCE" property is defined to
      occur only once for a specific component

   Description:  This component augments information provided by the
      "CONFERENCE" property for a virtual meeting or conference.
      Specifically, this specification adds support for long-form text
      and rich-text descriptions, which can not be provided in the
      "LABEL" parameter of the "CONFERENCE" property.

      A "VCONFERENCE" component by itself does not represent a virtual
      meeting and it does not replace information provided by the
      "CONFERENCE" property.  Instead, a calendar component that
      specifies the "VCONFERENCE" component MUST also specify a
      "CONFERENCE" property, and that "CONFERENCE" property value MUST
      match the value of the "URI" property (Section 4.3) specified in
      the "VCONFERENCE" component.  The URI values MUST be equal
      character strings, as specified in Section 6 of [RFC3986].

      A "VCONFERENCE" component MAY contain one "DESCRIPTION" property
      and multiple "STYLED-DESCRIPTION" properties, but one of them MUST
      NOT specify the "DERIVED" parameter and all others MUST specify
      the "DERIVED" parameter (e.g. it must have one and only one non-
      derived description).  For future extensibility, this
      specification does not define the "DESCRIPTION" or "STYLED-
      DESCRIPTION" properties to be mandatory, but a "VCONFERENCE"
      component MUST contain at least one property other than the "URI"
      property.

      Implementations that are unaware of the "VCONFERENCE" component
      might inadvertently preserve this component when removing its
      related "CONFERENCE" property from the calendar object.  Changing
      the URI value of the "CONFERENCE" property is in this context
      considered a removal followed by inserting a new element.
      Implementations SHOULD therefore ignore rather than reject such
      incorrectly specified "VCONFERENCE" components.  They MUST NOT
      preserve the ill-specified component in the calendaring data.

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   Format Definition:
      vconfc    = "BEGIN" ":" "VCONFERENCE" CRLF
                  *(
                   ;
                   ; The following are REQUIRED,
                   ; but MUST NOT occur more than once.
                   ;
                   uriprop /
                   ;
                   ; The following are OPTIONAL,
                   ; but MUST NOT occur more than once.
                   ;
                   description /
                   ;
                   ; The following are OPTIONAL,
                   ; and MAY occur more than once
                   ;
                   styleddescription
                   ;
                   ;
                   ; The following are OPTIONAL,
                   ; and MAY occur more than once.
                   ;
                   x-prop / iana-prop
                   ;
                   )
                  "END" ":" "VCONFERENCE" CRLF

   Example(s):  The following is an example of this component:

      BEGIN:VCONFERENCE
      URI;VALUE=URI:https://chat.example.com/x?id=123456
      DESCRIPTION:This is the first in a series of sessions:\n
       ...
      END:VCONFERENCE
      CONFERENCE;VALUE=URI;FEATURE=AUDIO,VIDEO;
       LABEL=Product Brainstorming Session:https://chat.example.com/x?id=123456

6.  Security Considerations

   This specification extends [RFC5545].  The same security
   considerations as outlined in Section 7 of [RFC5545] apply.

7.  IANA Considerations

   TBD

8.  References

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8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, 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, DOI 10.17487/RFC5545, September 2009,
              <https://www.rfc-editor.org/info/rfc5545>.

   [RFC5870]  Mayrhofer, A. and C. Spanring, "A Uniform Resource
              Identifier for Geographic Locations ('geo' URI)",
              RFC 5870, DOI 10.17487/RFC5870, June 2010,
              <https://www.rfc-editor.org/info/rfc5870>.

   [RFC7986]  Daboo, C., "New Properties for iCalendar", RFC 7986,
              DOI 10.17487/RFC7986, October 2016,
              <https://www.rfc-editor.org/info/rfc7986>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC9073]  Douglass, M., "Event Publishing Extensions to iCalendar",
              RFC 9073, DOI 10.17487/RFC9073, August 2021,
              <https://www.rfc-editor.org/info/rfc9073>.

9.  Informative References

   [I-D.ietf-calext-jscalendar-icalendar]
              Stepanek, R., "JSCalendar: Converting from and to
              iCalendar", Work in Progress, Internet-Draft, draft-ietf-
              calext-jscalendar-icalendar, 12 May 2025,
              <https://datatracker.ietf.org/doc/draft-ietf-calext-
              jscalendar-icalendar/>.

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   [I-D.stepanek-jscalendarbis]
              Jenkins, N.M. and R. Stepanek, "JSCalendar: A JSON
              Representation of Calendar Data", Work in Progress,
              Internet-Draft, draft-stepanek-jscalendarbis, 12 May 2025,
              <https://datatracker.ietf.org/doc/draft-stepanek-
              jscalendarbis/>.

Author's Address

   Robert Stepanek
   Fastmail
   PO Box 234
   Collins St. West
   Melbourne VIC 8007
   Australia
   Email: rsto@fastmailteam.com

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