7Internet Engineering Task Force (IETF) C. Daboo
8Request for Comments: 7986 Apple Inc.
9Updates: 5545 October 2016
10Category: Standards Track
14 New Properties for iCalendar
18 This document defines a set of new properties for iCalendar data and
19 extends the use of some existing properties to the entire iCalendar
24 This is an Internet Standards Track document.
26 This document is a product of the Internet Engineering Task Force
27 (IETF). It represents the consensus of the IETF community. It has
28 received public review and has been approved for publication by the
29 Internet Engineering Steering Group (IESG). Further information on
30 Internet Standards is available in Section 2 of RFC 7841.
32 Information about the current status of this document, any errata,
33 and how to provide feedback on it may be obtained at
34 http://www.rfc-editor.org/info/rfc7986.
38 Copyright (c) 2016 IETF Trust and the persons identified as the
39 document authors. All rights reserved.
41 This document is subject to BCP 78 and the IETF Trust's Legal
42 Provisions Relating to IETF Documents
43 (http://trustee.ietf.org/license-info) in effect on the date of
44 publication of this document. Please review these documents
45 carefully, as they describe your rights and restrictions with respect
46 to this document. Code Components extracted from this document must
47 include Simplified BSD License text as described in Section 4.e of
48 the Trust Legal Provisions and are provided without warranty as
49 described in the Simplified BSD License.
58Daboo Standards Track [Page 1]
60RFC 7986 iCalendar Property Extensions October 2016
65 1. Introduction ....................................................3
66 2. Conventions Used in This Document ...............................3
67 3. Backwards-Compatible Extension Properties .......................3
68 4. Modifications to Calendar Components ............................4
69 5. Properties ......................................................5
70 5.1. NAME Property ..............................................5
71 5.2. DESCRIPTION Property .......................................6
72 5.3. UID Property ...............................................7
73 5.4. LAST-MODIFIED Property .....................................8
74 5.5. URL Property ...............................................8
75 5.6. CATEGORIES Property ........................................8
76 5.7. REFRESH-INTERVAL Property ..................................9
77 5.8. SOURCE Property ...........................................10
78 5.9. COLOR Property ............................................10
79 5.10. IMAGE Property ...........................................11
80 5.11. CONFERENCE Property ......................................13
81 6. Property Parameters ............................................14
82 6.1. DISPLAY Property Parameter ................................14
83 6.2. EMAIL Property Parameter ..................................15
84 6.3. FEATURE Property Parameter ................................16
85 6.4. LABEL Property Parameter ..................................17
86 7. Security Considerations ........................................18
87 8. Privacy Considerations .........................................18
88 9. IANA Considerations ............................................19
89 9.1. Property Registrations ....................................19
90 9.2. Parameter Registrations ...................................20
91 9.3. Property Parameter Value Registries .......................20
92 10. References ....................................................21
93 10.1. Normative References .....................................21
94 10.2. Informative References ...................................22
95 Acknowledgments ...................................................23
96 Author's Address ..................................................23
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116RFC 7986 iCalendar Property Extensions October 2016
121 The iCalendar [RFC5545] data format is used to represent calendar
122 data and is used with the iCalendar Transport-Independent
123 Interoperability Protocol (iTIP) [RFC5546] to handle scheduling
124 operations between calendar users. iCalendar is in widespread use,
125 and in accordance with provisions in that specification, extension
126 elements have been added by various vendors to the data format in
127 order to support and enhance capabilities. This specification
128 collects a number of these ad hoc extensions and uses the new IANA
129 registry capability defined in [RFC5545] to register standard
130 variants with clearly defined definitions and semantics. In
131 addition, some new elements are introduced for features that vendors
132 have recently been requesting.
1342. Conventions Used in This Document
136 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
137 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
138 "OPTIONAL" in this document are to be interpreted as described in
141 The notation used in this memo is the ABNF notation of [RFC5234] as
142 used by iCalendar [RFC5545]. Any syntax elements shown below that
143 are not explicitly defined in this specification come from iCalendar
1463. Backwards-Compatible Extension Properties
148 iCalendar defines properties that can have different value types
149 indicated by a "VALUE" parameter. The definition of a property
150 specifies a "default" value type that is assumed to be used when no
151 "VALUE" parameter is present. However, this poses a problem to the
152 iCalendar parser/generator software that does not know about the
153 default values for new properties. For example, if a new property
154 "FOO" were defined with a default value type of URI and a URI value
155 with a comma was used, an iCalendar generator not aware of this fact
156 would likely treat the property value as "TEXT" and apply backslash
157 escaping to the comma in the value, effectively making it an invalid
160 To avoid this problem, this specification recommends that all
161 properties not defined in [RFC5545] always include a "VALUE"
162 parameter if the type is other than "TEXT". That is, in the example
163 above, the "FOO" property would have a "VALUE=URI" parameter. This
164 allows iCalendar parser/generator software to track the correct types
165 of unknown properties.
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172RFC 7986 iCalendar Property Extensions October 2016
175 New properties defined in this specification use the term "no
176 default" in the "Value Type" definition to indicate that the "VALUE"
177 parameter has to be included.
1794. Modifications to Calendar Components
181 This section details changes to the syntax defined in iCalendar
182 [RFC5545]. New elements are defined in subsequent sections.
186 ; The following are OPTIONAL,
187 ; but MUST NOT occur more than once.
189 uid / last-mod / url /
190 refresh / source / color
192 ; The following are OPTIONAL,
193 ; and MAY occur more than once.
195 name / description / categories /
202 ; The following are OPTIONAL,
203 ; but MUST NOT occur more than once.
207 ; The following are OPTIONAL,
208 ; and MAY occur more than once.
216 ; The following are OPTIONAL,
217 ; but MUST NOT occur more than once.
221 ; The following are OPTIONAL,
222 ; and MAY occur more than once.
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228RFC 7986 iCalendar Property Extensions October 2016
238 ; The following are OPTIONAL,
239 ; but MUST NOT occur more than once.
243 ; The following are OPTIONAL,
244 ; and MAY occur more than once.
256 Purpose: This property specifies the name of the calendar.
260 Property Parameters: IANA, non-standard, alternate text
261 representation, and language property parameters can be specified
264 Conformance: This property can be specified multiple times in an
265 iCalendar object. However, each property MUST represent the name
266 of the calendar in a different language.
268 Description: This property is used to specify a name of the
269 iCalendar object that can be used by calendar user agents when
270 presenting the calendar data to a user. Whilst a calendar only
271 has a single name, multiple language variants can be specified by
272 including this property multiple times with different "LANGUAGE"
273 parameter values on each.
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284RFC 7986 iCalendar Property Extensions October 2016
287 Format Definition: This property is defined by the following
290 name = "NAME" nameparam ":" text CRLF
294 ; The following are OPTIONAL,
295 ; but MUST NOT occur more than once.
297 (";" altrepparam) / (";" languageparam) /
299 ; The following is OPTIONAL,
300 ; and MAY occur more than once.
306 Example: The following is an example of this property:
308 NAME:Company Vacation Days
3105.2. DESCRIPTION Property
312 This specification modifies the definition of the "DESCRIPTION"
313 property to allow it to be defined in an iCalendar object. The
314 following additions are made to the definition of this property,
315 originally specified in Section 3.8.1.5 of [RFC5545].
317 Purpose: This property specifies the description of the calendar.
319 Conformance: This property can be specified multiple times in an
320 iCalendar object. However, each property MUST represent the
321 description of the calendar in a different language.
323 Description: This property is used to specify a lengthy textual
324 description of the iCalendar object that can be used by calendar
325 user agents when describing the nature of the calendar data to a
326 user. Whilst a calendar only has a single description, multiple
327 language variants can be specified by including this property
328 multiple times with different "LANGUAGE" parameter values on each.
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340RFC 7986 iCalendar Property Extensions October 2016
345 This specification modifies the definition of the "UID" property to
346 allow it to be defined in an iCalendar object. The following
347 additions are made to the definition of this property, originally
348 specified in Section 3.8.4.7 of [RFC5545].
350 Purpose: This property specifies the persistent, globally unique
351 identifier for the iCalendar object. This can be used, for
352 example, to identify duplicate calendar streams that a client may
353 have been given access to. It can be used in conjunction with the
354 "LAST-MODIFIED" property also specified on the "VCALENDAR" object
355 to identify the most recent version of a calendar.
357 Conformance: This property can be specified once in an iCalendar
360 The description of the "UID" property in [RFC5545] contains some
361 recommendations on how the value can be constructed. In particular,
362 it suggests use of host names, IP addresses, and domain names to
363 construct the value. However, this is no longer considered good
364 practice, particularly from a security and privacy standpoint, since
365 use of such values can leak key information about a calendar user or
366 their client and network environment. This specification updates
367 [RFC5545] by stating that "UID" values MUST NOT include any data that
368 might identify a user, host, domain, or any other security- or
369 privacy-sensitive information. It is RECOMMENDED that calendar user
370 agents now generate "UID" values that are hex-encoded random
371 Universally Unique Identifier (UUID) values as defined in
372 Sections 4.4 and 4.5 of [RFC4122].
374 The following is an example of such a property value:
376 UID:5FC53010-1267-4F8E-BC28-1D7AE55A7C99
378 Additionally, if calendar user agents choose to use other forms of
379 opaque identifiers for the "UID" value, they MUST have a length less
380 than 255 octets and MUST conform to the "iana-token" ABNF syntax
381 defined in Section 3.1 of [RFC5545].
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3995.4. LAST-MODIFIED Property
401 This specification modifies the definition of the "LAST-MODIFIED"
402 property to allow it to be defined in an iCalendar object. The
403 following additions are made to the definition of this property,
404 originally specified in Section 3.8.7.3 of [RFC5545].
406 Purpose: This property specifies the date and time that the
407 information associated with the calendar was last revised.
409 Conformance: This property can be specified once in an iCalendar
414 This specification modifies the definition of the "URL" property to
415 allow it to be defined in an iCalendar object. The following
416 additions are made to the definition of this property, originally
417 specified in Section 3.8.4.6 of [RFC5545].
419 Purpose: This property may be used to convey a location where a more
420 dynamic rendition of the calendar information can be found.
422 Conformance: This property can be specified once in an iCalendar
4255.6. CATEGORIES Property
427 This specification modifies the definition of the "CATEGORIES"
428 property to allow it to be defined in an iCalendar object. The
429 following additions are made to the definition of this property,
430 originally specified in Section 3.8.1.2 of [RFC5545].
432 Purpose: This property defines the categories for an entire
435 Conformance: This property can be specified multiple times in an
438 Description: When multiple properties are present, the set of
439 categories that apply to the iCalendar object are the union of all
440 the categories listed in each property value.
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452RFC 7986 iCalendar Property Extensions October 2016
4555.7. REFRESH-INTERVAL Property
457 Property Name: REFRESH-INTERVAL
459 Purpose: This property specifies a suggested minimum interval for
460 polling for changes of the calendar data from the original source
463 Value Type: DURATION -- no default
465 Property Parameters: IANA and non-standard property parameters can
466 be specified on this property.
468 Conformance: This property can be specified once in an iCalendar
471 Description: This property specifies a positive duration that gives
472 a suggested minimum polling interval for checking for updates to
473 the calendar data. The value of this property SHOULD be used by
474 calendar user agents to limit the polling interval for calendar
475 data updates to the minimum interval specified.
477 Format Definition: This property is defined by the following
480 refresh = "REFRESH-INTERVAL" refreshparam
482 ;consisting of a positive duration of time.
486 ; The following is REQUIRED,
487 ; but MUST NOT occur more than once.
489 (";" "VALUE" "=" "DURATION") /
491 ; The following is OPTIONAL,
492 ; and MAY occur more than once.
498 Example: The following is an example of this property:
500 REFRESH-INTERVAL;VALUE=DURATION:P1W
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508RFC 7986 iCalendar Property Extensions October 2016
513 Property Name: SOURCE
515 Purpose: This property identifies a URI where calendar data can be
518 Value Type: URI -- no default
520 Property Parameters: IANA and non-standard property parameters can
521 be specified on this property.
523 Conformance: This property can be specified once in an iCalendar
526 Description: This property identifies a location where a client can
527 retrieve updated data for the calendar. Clients SHOULD honor any
528 specified "REFRESH-INTERVAL" value when periodically retrieving
529 data. Note that this property differs from the "URL" property in
530 that "URL" is meant to provide an alternative representation of
531 the calendar data rather than the original location of the data.
533 Format Definition: This property is defined by the following
536 source = "SOURCE" sourceparam ":" uri CRLF
538 sourceparam = *(";" other-param)
540 Example: The following is an example of this property:
542 SOURCE;VALUE=URI:https://example.com/holidays.ics
548 Purpose: This property specifies a color used for displaying the
549 calendar, event, todo, or journal data.
553 Property Parameters: IANA and non-standard property parameters can
554 be specified on this property.
556 Conformance: This property can be specified once in an iCalendar
557 object or in "VEVENT", "VTODO", or "VJOURNAL" calendar components.
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564RFC 7986 iCalendar Property Extensions October 2016
567 Description: This property specifies a color that clients MAY use
568 when presenting the relevant data to a user. Typically, this
569 would appear as the "background" color of events or tasks. The
570 value is a case-insensitive color name taken from the CSS3 set of
571 names, defined in Section 4.3 of [W3C.REC-css3-color-20110607].
573 Format Definition: This property is defined by the following
576 color = "COLOR" colorparam ":" text CRLF
577 ; Value is CSS3 color name
579 colorparam = *(";" other-param)
581 Example: The following is an example of this property:
589 Purpose: This property specifies an image associated with the
590 calendar or a calendar component.
592 Value Type: URI or BINARY -- no default. The value MUST be data
593 with a media type of "image" or refer to such data.
595 Property Parameters: IANA, non-standard, display, inline encoding,
596 and value data type property parameters can be specified on this
597 property. The format type parameter can be specified on this
598 property and is RECOMMENDED for inline binary-encoded content
601 Conformance: This property can be specified multiple times in an
602 iCalendar object or in "VEVENT", "VTODO", or "VJOURNAL" calendar
605 Description: This property specifies an image for an iCalendar
606 object or a calendar component via a URI or directly with inline
607 data that can be used by calendar user agents when presenting the
608 calendar data to a user. Multiple properties MAY be used to
609 specify alternative sets of images with, for example, varying
610 media subtypes, resolutions, or sizes. When multiple properties
611 are present, calendar user agents SHOULD display only one of them,
612 picking one that provides the most appropriate image quality, or
613 display none. The "DISPLAY" parameter is used to indicate the
614 intended display mode for the image. The "ALTREP" parameter,
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623 defined in [RFC5545], can be used to provide a "clickable" image
624 where the URI in the parameter value can be "launched" by a click
625 on the image in the calendar user agent.
627 Format Definition: This property is defined by the following
630 image = "IMAGE" imageparam
633 ";" "VALUE" "=" "URI"
637 ";" "ENCODING" "=" "BASE64"
638 ";" "VALUE" "=" "BINARY"
646 ; The following is OPTIONAL for a URI value,
647 ; RECOMMENDED for a BINARY value,
648 ; and MUST NOT occur more than once.
652 ; The following are OPTIONAL,
653 ; and MUST NOT occur more than once.
655 (";" altrepparam) / (";" displayparam) /
657 ; The following is OPTIONAL,
658 ; and MAY occur more than once.
664 Example: The following is an example of this property:
666 IMAGE;VALUE=URI;DISPLAY=BADGE;FMTTYPE=image/png:h
667 ttp://example.com/images/party.png
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6795.11. CONFERENCE Property
681 Property Name: CONFERENCE
683 Purpose: This property specifies information for accessing a
686 Value Type: URI -- no default.
688 Property Parameters: IANA, non-standard, feature, and label property
689 parameters can be specified on this property.
691 Conformance: This property can be specified multiple times in a
692 "VEVENT" or "VTODO" calendar component.
694 Description: This property specifies information for accessing a
695 conferencing system for attendees of a meeting or task. This
696 might be for a telephone-based conference number dial-in with
697 access codes included (such as a tel: URI [RFC3966] or a sip: or
698 sips: URI [RFC3261]), for a web-based video chat (such as an http:
699 or https: URI [RFC7230]), or for an instant messaging group chat
700 room (such as an xmpp: URI [RFC5122]). If a specific URI for a
701 conferencing system is not available, a data: URI [RFC2397]
702 containing a text description can be used.
704 A conference system can be a bidirectional communication channel
705 or a uni-directional "broadcast feed".
707 The "FEATURE" property parameter is used to describe the key
708 capabilities of the conference system to allow a client to choose
709 the ones that give the required level of interaction from a set of
712 The "LABEL" property parameter is used to convey additional
713 details on the use of the URI. For example, the URIs or access
714 codes for the moderator and attendee of a teleconference system
715 could be different, and the "LABEL" property parameter could be
716 used to "tag" each "CONFERENCE" property to indicate which is
719 The "LANGUAGE" property parameter can be used to specify the
720 language used for text values used with this property (as per
721 Section 3.2.10 of [RFC5545]).
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735 Format Definition: This property is defined by the following
738 conference = "CONFERENCE" confparam ":" uri CRLF
742 ; The following is REQUIRED,
743 ; but MUST NOT occur more than once.
745 (";" "VALUE" "=" "URI") /
747 ; The following are OPTIONAL,
748 ; and MUST NOT occur more than once.
750 (";" featureparam) / (";" labelparam) /
751 (";" languageparam ) /
753 ; The following is OPTIONAL,
754 ; and MAY occur more than once.
760 Example: The following are examples of this property:
762 CONFERENCE;VALUE=URI;FEATURE=PHONE,MODERATOR;
763 LABEL=Moderator dial-in:tel:+1-412-555-0123,,,654321
764 CONFERENCE;VALUE=URI;FEATURE=PHONE;
765 LABEL=Attendee dial-in:tel:+1-412-555-0123,,,555123
766 CONFERENCE;VALUE=URI;FEATURE=PHONE;
767 LABEL=Attendee dial-in:tel:+1-888-555-0456,,,555123
768 CONFERENCE;VALUE=URI;FEATURE=CHAT;
769 LABEL=Chat room:xmpp:chat-123@conference.example.com
770 CONFERENCE;VALUE=URI;FEATURE=AUDIO,VIDEO;
771 LABEL=Attendee dial-in:https://chat.example.com/audio?id=123456
7736. Property Parameters
7756.1. DISPLAY Property Parameter
777 Parameter Name: DISPLAY
779 Purpose: To specify different ways in which an image for a calendar
780 or component can be displayed.
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788RFC 7986 iCalendar Property Extensions October 2016
791 Format Definition: This property parameter is defined by the
794 displayparam = "DISPLAY" "=" displayval *("," displayval)
796 displayval = ("BADGE" / ; image inline with the title of the
798 "GRAPHIC" / ; a full image replacement for the event
800 "FULLSIZE" / ; an image that is used to enhance the
802 "THUMBNAIL" / ; a smaller variant of "FULLSIZE" to be
803 ; used when space for the image is
805 x-name / ; Experimental type
806 iana-token) ; Other IANA-registered type
810 Description: This property parameter MAY be specified on "IMAGE"
811 properties. In the absence of this parameter, the default value
812 "BADGE" MUST be used. The value determines how a client ought to
813 present an image supplied in iCalendar data to the user.
815 Values for this parameter are registered with IANA as per
816 Section 9.3.1. New values can be added to this registry following
817 the procedure outlined in Section 8.2.1 of [RFC5545].
819 Servers and clients MUST handle x-name and iana-token values they
820 don't recognize by not displaying any image at all.
824 IMAGE;VALUE=URI;DISPLAY=BADGE,THUMBNAIL;FMTTYPE=image/png:https://exa
825 mple.com/images/weather-cloudy.png
8276.2. EMAIL Property Parameter
829 Parameter Name: EMAIL
831 Purpose: To specify an email address that is used to identify or
832 contact an organizer or attendee.
834 Format Definition: This property parameter is defined by the
837 emailparam = "EMAIL" "=" param-value
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847 Description: This property parameter MAY be specified on "ORGANIZER"
848 or "ATTENDEE" properties. This property can be used in situations
849 where the calendar user address value of the "ORGANIZER" and
850 "ATTENDEE" properties is not likely to be an identifier that
851 recipients of scheduling messages could use to match the calendar
852 user with, for example, an address book entry. The value of this
853 property is an email address that can easily be matched by
854 recipients. Recipients can also use this value as an alternative
855 means of contacting the calendar user via email. If a recipient's
856 calendar user agent allows the recipient to save contact
857 information based on the "ORGANIZER" or "ATTENDEE" properties,
858 those calendar user agents SHOULD use any "EMAIL" property
859 parameter value for the email address of the contact over any
860 mailto: calendar user address specified as the value of the
861 property. Calendar user agents SHOULD NOT include an "EMAIL"
862 property parameter when its value matches the calendar user
863 address specified as the value of the property.
867 ATTENDEE;CN=Cyrus Daboo;EMAIL=cyrus@example.com:mailto:opaque-toke
8706.3. FEATURE Property Parameter
872 Parameter Name: FEATURE
874 Purpose: To specify a feature or features of a conference or
877 Format Definition: This property parameter is defined by the
880 featureparam = "FEATURE" "=" featuretext *("," featuretext)
881 featuretext = ("AUDIO" / ; Audio capability
882 "CHAT" / ; Chat or instant messaging
883 "FEED" / ; Blog or Atom feed
884 "MODERATOR" / ; Moderator dial-in code
885 "PHONE" / ; Phone conference
886 "SCREEN" / ; Screen sharing
887 "VIDEO" / ; Video capability
888 x-name / ; Experimental type
889 iana-token) ; Other IANA-registered type
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903 Description: This property parameter MAY be specified on the
904 "CONFERENCE" property. Multiple values can be specified. The
905 "MODERATOR" value is used to indicate that the property value is
906 specific to the owner/initiator of the conference and contains a
907 URI that "activates" the system (e.g., a "moderator" access code
908 for a phone conference system that is different from the "regular"
913 CONFERENCE;VALUE=URI;FEATURE=AUDIO:rtsp://audio.example.com/
915 CONFERENCE;VALUE=URI;FEATURE=AUDIO,VIDEO:https://video-chat.exam
916 ple.com/;group-id=1234
9186.4. LABEL Property Parameter
920 Parameter Name: LABEL
922 Purpose: To provide a human-readable label.
924 Format Definition: This property parameter is defined by the
927 labelparam = "LABEL" "=" param-value
929 Description: This property parameter MAY be specified on the
930 "CONFERENCE" property. It is anticipated that other extensions to
931 iCalendar will reuse this property parameter on new properties
932 that they define. As a result, clients MUST expect to find this
933 property parameter present on many different properties. It
934 provides a human-readable label that can be presented to calendar
935 users to allow them to discriminate between properties that might
936 be similar or provide additional information for properties that
937 are not self-describing. The "LANGUAGE" property parameter can be
938 used to specify the language of the text in the parameter value
939 (as per Section 3.2.10 of [RFC5545]).
943 CONFERENCE;VALUE=URI;FEATURE=VIDEO;
944 LABEL="Web video chat, access code=76543";
945 :https://video-chat.example.com/;group-id=1234
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9597. Security Considerations
961 Several of the new properties or parameters defined by this
962 specification allow reference to "external" URIs. Care MUST be taken
963 when accessing data at external URIs as malicious content could be
964 present. Clients SHOULD ensure that suitable permission is granted
965 by calendar users before such URIs are dereferenced.
967 The "REFRESH-INTERVAL" property could be used by an attacker to make
968 a client carry out rapid requests to the server hosting the calendar
969 by specifying a very short duration (e.g., one second). This could
970 lead to resource consumption on the client or server and to denial-
971 of-service attacks against the server. Clients MUST ensure that they
972 throttle requests to the server to a reasonable rate. In most cases,
973 updating a public calendar once per day would suffice. If the
974 "REFRESH-INTERVAL" is any less than that, clients SHOULD warn the
975 calendar user and allow them to override it with a longer value.
977 The "CONFERENCE" property can include a "FEATURE" property parameter
978 with a "MODERATOR" value. In some cases, the access code used by the
979 owner/initiator of a conference might be private to an individual,
980 and clients and servers MUST ensure that such properties are not sent
981 to attendees of a scheduled component.
983 Both the "COLOR" and "IMAGE" properties are likely to be used by
984 calendar users to express their own personal view of the calendar
985 data. In addition, these properties could be used by attackers to
986 produce a confusing display in a calendar user agent. When such
987 properties are encountered in calendar data that has come from other
988 calendar users (e.g., via a scheduling message, "public" calendar
989 subscription, etc.), it is advisable for the client to give the
990 receiving calendar user the option to remove (or adjust) these
991 properties as the data is imported into their calendar system.
993 This specification changes the recommendations on how "UID" property
994 values are constructed to minimize leaking any information that might
995 be security sensitive.
997 Security considerations in [RFC5545] and [RFC5546] MUST also be
10008. Privacy Considerations
1002 Several of the new properties or parameters defined by this
1003 specification allow reference to "external" URIs. Access to those
1004 URIs could be tracked, leading to loss of privacy. Clients SHOULD
1005 ensure that suitable permission is granted by calendar users before
1006 such URIs are dereferenced. In particular, calendar publishers
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1012RFC 7986 iCalendar Property Extensions October 2016
1015 wishing to help protect the privacy of their subscribers MUST use
1016 HTTP with Transport Layer Security [RFC7230] ("https:" URIs instead
1017 of "http:" URIs) for access to calendar data or ancillary data such
1020 In general, for their own privacy protection, users have to rely on
1021 the privacy policies of any conferencing system being accessed via
1022 the "CONFERENCE" property. It is entirely possible for such systems
1023 to uniquely identify and log the activity and participation (or lack
1024 thereof) of calendar users in the conference. Calendar user agents
1025 SHOULD track which conferencing systems are used and warn users the
1026 first time a new one is about to be used. This is particularly
1027 important if the client automatically "dials in" to the conference
1028 when the event start time occurs.
1030 By giving different calendar users different values for the "REFRESH-
1031 INTERVAL" property, it is possible for a publisher of calendar data
1032 to uniquely identify each refresh from each calendar users' clients
1033 and thereby track user activity and IP address over time. To address
1034 this, clients SHOULD add or subtract some random amount of time from
1035 the published "REFRESH-INTERVAL" value when doing actual refreshes.
1037 This specification changes the recommendations on how "UID" property
1038 values are constructed to minimize leaking any information that might
1039 be privacy sensitive.
1041 Privacy considerations in [RFC5545] and [RFC5546] MUST also be
10449. IANA Considerations
10469.1. Property Registrations
1048 This document defines the following new iCalendar properties. IANA
1049 has registered the new properties in the "Properties" registry
1050 defined in Section 8.3.2 of [RFC5545]. IANA has also added a
1051 reference to this document where the properties originally defined in
1052 RFC 5545 have been updated by this document.
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1068RFC 7986 iCalendar Property Extensions October 2016
1071 +------------------+---------+--------------------------------------+
1072 | Property | Status | Reference |
1073 +------------------+---------+--------------------------------------+
1074 | NAME | Current | RFC 7986, Section 5.1 |
1075 | DESCRIPTION | Current | RFC 5545, Section 3.8.1.5; RFC 7986, |
1077 | UID | Current | RFC 5545, Section 3.8.4.7; RFC 7986, |
1079 | LAST-MODIFIED | Current | RFC 5545, Section 3.8.7.3 RFC 7986, |
1081 | URL | Current | RFC 5545, Section 3.8.4.6; RFC 7986, |
1083 | CATEGORIES | Current | RFC 5545, Section 3.8.1.2; RFC 7986, |
1085 | REFRESH-INTERVAL | Current | RFC 7986, Section 5.7 |
1086 | SOURCE | Current | RFC 7986, Section 5.8 |
1087 | COLOR | Current | RFC 7986, Section 5.9 |
1088 | IMAGE | Current | RFC 7986, Section 5.10 |
1089 | CONFERENCE | Current | RFC 7986, Section 5.11 |
1090 +------------------+---------+--------------------------------------+
10929.2. Parameter Registrations
1094 This document defines the following new iCalendar property
1095 parameters. IANA has registered these in the "Parameters" registry
1096 defined in Section 8.3.3 of [RFC5545].
1098 +--------------------+---------+-----------------------+
1099 | Property Parameter | Status | Reference |
1100 +--------------------+---------+-----------------------+
1101 | DISPLAY | Current | RFC 7986, Section 6.1 |
1102 | EMAIL | Current | RFC 7986, Section 6.2 |
1103 | FEATURE | Current | RFC 7986, Section 6.3 |
1104 | LABEL | Current | RFC 7986, Section 6.4 |
1105 +--------------------+---------+-----------------------+
11079.3. Property Parameter Value Registries
1109 IANA has created two new registries for iCalendar elements: the
1110 "Display Types" registry and the "Feature Types" registry.
1111 Additional codes MAY be used, provided the process and template
1112 described in Sections 8.2.1 and 8.2.6 of [RFC5545] are used to
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1124RFC 7986 iCalendar Property Extensions October 2016
11279.3.1. Display Types Registry
1129 The following table has been used to initialize the "Display Types"
1132 +--------------+---------+-----------------------+
1133 | Display Type | Status | Reference |
1134 +--------------+---------+-----------------------+
1135 | BADGE | Current | RFC 7986, Section 6.1 |
1136 | GRAPHIC | Current | RFC 7986, Section 6.1 |
1137 | FULLSIZE | Current | RFC 7986, Section 6.1 |
1138 | THUMBNAIL | Current | RFC 7986, Section 6.1 |
1139 +--------------+---------+-----------------------+
11419.3.2. Feature Types Registry
1143 The following table has been used to initialize the "Feature Types"
1146 +--------------+---------+-----------------------+
1147 | Feature Type | Status | Reference |
1148 +--------------+---------+-----------------------+
1149 | AUDIO | Current | RFC 7986, Section 6.3 |
1150 | CHAT | Current | RFC 7986, Section 6.3 |
1151 | FEED | Current | RFC 7986, Section 6.3 |
1152 | MODERATOR | Current | RFC 7986, Section 6.3 |
1153 | PHONE | Current | RFC 7986, Section 6.3 |
1154 | SCREEN | Current | RFC 7986, Section 6.3 |
1155 | VIDEO | Current | RFC 7986, Section 6.3 |
1156 +--------------+---------+-----------------------+
116010.1. Normative References
1162 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
1163 Requirement Levels", BCP 14, RFC 2119,
1164 DOI 10.17487/RFC2119, March 1997,
1165 <http://www.rfc-editor.org/info/rfc2119>.
1167 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
1168 Unique IDentifier (UUID) URN Namespace", RFC 4122,
1169 DOI 10.17487/RFC4122, July 2005,
1170 <http://www.rfc-editor.org/info/rfc4122>.
1178Daboo Standards Track [Page 21]
1180RFC 7986 iCalendar Property Extensions October 2016
1183 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
1184 Specifications: ABNF", STD 68, RFC 5234,
1185 DOI 10.17487/RFC5234, January 2008,
1186 <http://www.rfc-editor.org/info/rfc5234>.
1188 [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and
1189 Scheduling Core Object Specification (iCalendar)",
1190 RFC 5545, DOI 10.17487/RFC5545, September 2009,
1191 <http://www.rfc-editor.org/info/rfc5545>.
1193 [RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent
1194 Interoperability Protocol (iTIP)", RFC 5546,
1195 DOI 10.17487/RFC5546, December 2009,
1196 <http://www.rfc-editor.org/info/rfc5546>.
1198 [W3C.REC-css3-color-20110607]
1199 Celik, T., Lilley, C., and D. Baron, "CSS Color Module
1200 Level 3", World Wide Web Consortium Recommendation
1201 REC-css3-color-20110607, June 2011,
1202 <https://www.w3.org/TR/2011/REC-css3-color-20110607>.
120410.2. Informative References
1206 [RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397,
1207 DOI 10.17487/RFC2397, August 1998,
1208 <http://www.rfc-editor.org/info/rfc2397>.
1210 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
1211 A., Peterson, J., Sparks, R., Handley, M., and E.
1212 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
1213 DOI 10.17487/RFC3261, June 2002,
1214 <http://www.rfc-editor.org/info/rfc3261>.
1216 [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
1217 RFC 3966, DOI 10.17487/RFC3966, December 2004,
1218 <http://www.rfc-editor.org/info/rfc3966>.
1220 [RFC5122] Saint-Andre, P., "Internationalized Resource Identifiers
1221 (IRIs) and Uniform Resource Identifiers (URIs) for the
1222 Extensible Messaging and Presence Protocol (XMPP)",
1223 RFC 5122, DOI 10.17487/RFC5122, February 2008,
1224 <http://www.rfc-editor.org/info/rfc5122>.
1226 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
1227 Protocol (HTTP/1.1): Message Syntax and Routing",
1228 RFC 7230, DOI 10.17487/RFC7230, June 2014,
1229 <http://www.rfc-editor.org/info/rfc7230>.
1234Daboo Standards Track [Page 22]
1236RFC 7986 iCalendar Property Extensions October 2016
1241 Thanks to the following individuals for feedback: Bernard
1242 Desruisseaux, Mike Douglass, Lucia Fedorova, Ken Murchison, Arnaud
1243 Quillaud, and Dave Thewlis.
1245 This specification came about via discussions at the Calendaring and
1246 Scheduling Consortium.
1254 United States of America
1256 Email: cyrus@daboo.name
1257 URI: http://www.apple.com/
1290Daboo Standards Track [Page 23]