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+Internet Engineering Task Force (IETF) C. Daboo
+Request for Comments: 7986 Apple Inc.
+Updates: 5545 October 2016
+Category: Standards Track
+ISSN: 2070-1721
+
+
+ New Properties for iCalendar
+
+Abstract
+
+ This document defines a set of new properties for iCalendar data and
+ extends the use of some existing properties to the entire iCalendar
+ object.
+
+Status of This Memo
+
+ This is an Internet Standards Track document.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Further information on
+ Internet Standards is available in Section 2 of RFC 7841.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ http://www.rfc-editor.org/info/rfc7986.
+
+Copyright Notice
+
+ Copyright (c) 2016 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
+ Provisions Relating to IETF Documents
+ (http://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 Simplified BSD License text as described in Section 4.e of
+ the Trust Legal Provisions and are provided without warranty as
+ described in the Simplified BSD License.
+
+
+
+
+
+
+
+
+Daboo Standards Track [Page 1]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+Table of Contents
+
+ 1. Introduction ....................................................3
+ 2. Conventions Used in This Document ...............................3
+ 3. Backwards-Compatible Extension Properties .......................3
+ 4. Modifications to Calendar Components ............................4
+ 5. Properties ......................................................5
+ 5.1. NAME Property ..............................................5
+ 5.2. DESCRIPTION Property .......................................6
+ 5.3. UID Property ...............................................7
+ 5.4. LAST-MODIFIED Property .....................................8
+ 5.5. URL Property ...............................................8
+ 5.6. CATEGORIES Property ........................................8
+ 5.7. REFRESH-INTERVAL Property ..................................9
+ 5.8. SOURCE Property ...........................................10
+ 5.9. COLOR Property ............................................10
+ 5.10. IMAGE Property ...........................................11
+ 5.11. CONFERENCE Property ......................................13
+ 6. Property Parameters ............................................14
+ 6.1. DISPLAY Property Parameter ................................14
+ 6.2. EMAIL Property Parameter ..................................15
+ 6.3. FEATURE Property Parameter ................................16
+ 6.4. LABEL Property Parameter ..................................17
+ 7. Security Considerations ........................................18
+ 8. Privacy Considerations .........................................18
+ 9. IANA Considerations ............................................19
+ 9.1. Property Registrations ....................................19
+ 9.2. Parameter Registrations ...................................20
+ 9.3. Property Parameter Value Registries .......................20
+ 10. References ....................................................21
+ 10.1. Normative References .....................................21
+ 10.2. Informative References ...................................22
+ Acknowledgments ...................................................23
+ Author's Address ..................................................23
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Daboo Standards Track [Page 2]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+1. Introduction
+
+ The iCalendar [RFC5545] data format is used to represent calendar
+ data and is used with the iCalendar Transport-Independent
+ Interoperability Protocol (iTIP) [RFC5546] to handle scheduling
+ operations between calendar users. iCalendar is in widespread use,
+ and in accordance with provisions in that specification, extension
+ elements have been added by various vendors to the data format in
+ order to support and enhance capabilities. This specification
+ collects a number of these ad hoc extensions and uses the new IANA
+ registry capability defined in [RFC5545] to register standard
+ variants with clearly defined definitions and semantics. In
+ addition, some new elements are introduced for features that vendors
+ have recently been requesting.
+
+2. Conventions Used in This Document
+
+ 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 is the ABNF notation of [RFC5234] as
+ used by iCalendar [RFC5545]. Any syntax elements shown below that
+ are not explicitly defined in this specification come from iCalendar
+ [RFC5545].
+
+3. Backwards-Compatible Extension Properties
+
+ iCalendar defines properties that can have different value types
+ indicated by a "VALUE" parameter. The definition of a property
+ specifies a "default" value type that is assumed to be used when no
+ "VALUE" parameter is present. However, this poses a problem to the
+ iCalendar parser/generator software that does not know about the
+ default values for new properties. For example, if a new property
+ "FOO" were defined with a default value type of URI and a URI value
+ with a comma was used, an iCalendar generator not aware of this fact
+ would likely treat the property value as "TEXT" and apply backslash
+ escaping to the comma in the value, effectively making it an invalid
+ URI value.
+
+ To avoid this problem, this specification recommends that all
+ properties not defined in [RFC5545] always include a "VALUE"
+ parameter if the type is other than "TEXT". That is, in the example
+ above, the "FOO" property would have a "VALUE=URI" parameter. This
+ allows iCalendar parser/generator software to track the correct types
+ of unknown properties.
+
+
+
+
+Daboo Standards Track [Page 3]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ New properties defined in this specification use the term "no
+ default" in the "Value Type" definition to indicate that the "VALUE"
+ parameter has to be included.
+
+4. Modifications to Calendar Components
+
+ This section details changes to the syntax defined in iCalendar
+ [RFC5545]. New elements are defined in subsequent sections.
+
+ calprops =/ *(
+ ;
+ ; The following are OPTIONAL,
+ ; but MUST NOT occur more than once.
+ ;
+ uid / last-mod / url /
+ refresh / source / color
+ ;
+ ; The following are OPTIONAL,
+ ; and MAY occur more than once.
+ ;
+ name / description / categories /
+ image
+ ;
+ )
+
+ eventprop =/ *(
+ ;
+ ; The following are OPTIONAL,
+ ; but MUST NOT occur more than once.
+ ;
+ color /
+ ;
+ ; The following are OPTIONAL,
+ ; and MAY occur more than once.
+ ;
+ conference / image
+ ;
+ )
+
+ todoprop =/ *(
+ ;
+ ; The following are OPTIONAL,
+ ; but MUST NOT occur more than once.
+ ;
+ color /
+ ;
+ ; The following are OPTIONAL,
+ ; and MAY occur more than once.
+
+
+
+Daboo Standards Track [Page 4]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ ;
+ conference / image
+ ;
+ )
+
+ jourprop =/ *(
+ ;
+ ; The following are OPTIONAL,
+ ; but MUST NOT occur more than once.
+ ;
+ color /
+ ;
+ ; The following are OPTIONAL,
+ ; and MAY occur more than once.
+ ;
+ image
+ ;
+ )
+
+5. Properties
+
+5.1. NAME Property
+
+ Property Name: NAME
+
+ Purpose: This property specifies the name of the calendar.
+
+ Value Type: TEXT
+
+ Property Parameters: IANA, non-standard, alternate text
+ representation, and language property parameters can be specified
+ on this property.
+
+ Conformance: This property can be specified multiple times in an
+ iCalendar object. However, each property MUST represent the name
+ of the calendar in a different language.
+
+ Description: This property is used to specify a name of the
+ iCalendar object that can be used by calendar user agents when
+ presenting the calendar data to a user. Whilst a calendar only
+ has a single name, multiple language variants can be specified by
+ including this property multiple times with different "LANGUAGE"
+ parameter values on each.
+
+
+
+
+
+
+
+
+Daboo Standards Track [Page 5]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ Format Definition: This property is defined by the following
+ notation:
+
+ name = "NAME" nameparam ":" text CRLF
+
+ nameparam = *(
+ ;
+ ; The following are OPTIONAL,
+ ; but MUST NOT occur more than once.
+ ;
+ (";" altrepparam) / (";" languageparam) /
+ ;
+ ; The following is OPTIONAL,
+ ; and MAY occur more than once.
+ ;
+ (";" other-param)
+ ;
+ )
+
+ Example: The following is an example of this property:
+
+ NAME:Company Vacation Days
+
+5.2. DESCRIPTION Property
+
+ This specification modifies the definition of the "DESCRIPTION"
+ property to allow it to be defined in an iCalendar object. The
+ following additions are made to the definition of this property,
+ originally specified in Section 3.8.1.5 of [RFC5545].
+
+ Purpose: This property specifies the description of the calendar.
+
+ Conformance: This property can be specified multiple times in an
+ iCalendar object. However, each property MUST represent the
+ description of the calendar in a different language.
+
+ Description: This property is used to specify a lengthy textual
+ description of the iCalendar object that can be used by calendar
+ user agents when describing the nature of the calendar data to a
+ user. Whilst a calendar only has a single description, multiple
+ language variants can be specified by including this property
+ multiple times with different "LANGUAGE" parameter values on each.
+
+
+
+
+
+
+
+
+
+Daboo Standards Track [Page 6]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+5.3. UID Property
+
+ This specification modifies the definition of the "UID" property to
+ allow it to be defined in an iCalendar object. The following
+ additions are made to the definition of this property, originally
+ specified in Section 3.8.4.7 of [RFC5545].
+
+ Purpose: This property specifies the persistent, globally unique
+ identifier for the iCalendar object. This can be used, for
+ example, to identify duplicate calendar streams that a client may
+ have been given access to. It can be used in conjunction with the
+ "LAST-MODIFIED" property also specified on the "VCALENDAR" object
+ to identify the most recent version of a calendar.
+
+ Conformance: This property can be specified once in an iCalendar
+ object.
+
+ The description of the "UID" property in [RFC5545] contains some
+ recommendations on how the value can be constructed. In particular,
+ it suggests use of host names, IP addresses, and domain names to
+ construct the value. However, this is no longer considered good
+ practice, particularly from a security and privacy standpoint, since
+ use of such values can leak key information about a calendar user or
+ their client and network environment. This specification updates
+ [RFC5545] by stating that "UID" values MUST NOT include any data that
+ might identify a user, host, domain, or any other security- or
+ privacy-sensitive information. It is RECOMMENDED that calendar user
+ agents now generate "UID" values that are hex-encoded random
+ Universally Unique Identifier (UUID) values as defined in
+ Sections 4.4 and 4.5 of [RFC4122].
+
+ The following is an example of such a property value:
+
+ UID:5FC53010-1267-4F8E-BC28-1D7AE55A7C99
+
+ Additionally, if calendar user agents choose to use other forms of
+ opaque identifiers for the "UID" value, they MUST have a length less
+ than 255 octets and MUST conform to the "iana-token" ABNF syntax
+ defined in Section 3.1 of [RFC5545].
+
+
+
+
+
+
+
+
+
+
+
+
+Daboo Standards Track [Page 7]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+5.4. LAST-MODIFIED Property
+
+ This specification modifies the definition of the "LAST-MODIFIED"
+ property to allow it to be defined in an iCalendar object. The
+ following additions are made to the definition of this property,
+ originally specified in Section 3.8.7.3 of [RFC5545].
+
+ Purpose: This property specifies the date and time that the
+ information associated with the calendar was last revised.
+
+ Conformance: This property can be specified once in an iCalendar
+ object.
+
+5.5. URL Property
+
+ This specification modifies the definition of the "URL" property to
+ allow it to be defined in an iCalendar object. The following
+ additions are made to the definition of this property, originally
+ specified in Section 3.8.4.6 of [RFC5545].
+
+ Purpose: This property may be used to convey a location where a more
+ dynamic rendition of the calendar information can be found.
+
+ Conformance: This property can be specified once in an iCalendar
+ object.
+
+5.6. CATEGORIES Property
+
+ This specification modifies the definition of the "CATEGORIES"
+ property to allow it to be defined in an iCalendar object. The
+ following additions are made to the definition of this property,
+ originally specified in Section 3.8.1.2 of [RFC5545].
+
+ Purpose: This property defines the categories for an entire
+ calendar.
+
+ Conformance: This property can be specified multiple times in an
+ iCalendar object.
+
+ Description: When multiple properties are present, the set of
+ categories that apply to the iCalendar object are the union of all
+ the categories listed in each property value.
+
+
+
+
+
+
+
+
+
+Daboo Standards Track [Page 8]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+5.7. REFRESH-INTERVAL Property
+
+ Property Name: REFRESH-INTERVAL
+
+ Purpose: This property specifies a suggested minimum interval for
+ polling for changes of the calendar data from the original source
+ of that data.
+
+ Value Type: DURATION -- no default
+
+ Property Parameters: IANA and non-standard property parameters can
+ be specified on this property.
+
+ Conformance: This property can be specified once in an iCalendar
+ object.
+
+ Description: This property specifies a positive duration that gives
+ a suggested minimum polling interval for checking for updates to
+ the calendar data. The value of this property SHOULD be used by
+ calendar user agents to limit the polling interval for calendar
+ data updates to the minimum interval specified.
+
+ Format Definition: This property is defined by the following
+ notation:
+
+ refresh = "REFRESH-INTERVAL" refreshparam
+ ":" dur-value CRLF
+ ;consisting of a positive duration of time.
+
+ refreshparam = *(
+ ;
+ ; The following is REQUIRED,
+ ; but MUST NOT occur more than once.
+ ;
+ (";" "VALUE" "=" "DURATION") /
+ ;
+ ; The following is OPTIONAL,
+ ; and MAY occur more than once.
+ ;
+ (";" other-param)
+ ;
+ )
+
+ Example: The following is an example of this property:
+
+ REFRESH-INTERVAL;VALUE=DURATION:P1W
+
+
+
+
+
+Daboo Standards Track [Page 9]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+5.8. SOURCE Property
+
+ Property Name: SOURCE
+
+ Purpose: This property identifies a URI where calendar data can be
+ refreshed from.
+
+ Value Type: URI -- no default
+
+ Property Parameters: IANA and non-standard property parameters can
+ be specified on this property.
+
+ Conformance: This property can be specified once in an iCalendar
+ object.
+
+ Description: This property identifies a location where a client can
+ retrieve updated data for the calendar. Clients SHOULD honor any
+ specified "REFRESH-INTERVAL" value when periodically retrieving
+ data. Note that this property differs from the "URL" property in
+ that "URL" is meant to provide an alternative representation of
+ the calendar data rather than the original location of the data.
+
+ Format Definition: This property is defined by the following
+ notation:
+
+ source = "SOURCE" sourceparam ":" uri CRLF
+
+ sourceparam = *(";" other-param)
+
+ Example: The following is an example of this property:
+
+ SOURCE;VALUE=URI:https://example.com/holidays.ics
+
+5.9. COLOR Property
+
+ Property Name: COLOR
+
+ Purpose: This property specifies a color used for displaying the
+ calendar, event, todo, or journal data.
+
+ Value Type: TEXT
+
+ Property Parameters: IANA and non-standard property parameters can
+ be specified on this property.
+
+ Conformance: This property can be specified once in an iCalendar
+ object or in "VEVENT", "VTODO", or "VJOURNAL" calendar components.
+
+
+
+
+Daboo Standards Track [Page 10]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ Description: This property specifies a color that clients MAY use
+ when presenting the relevant data to a user. Typically, this
+ would appear as the "background" color of events or tasks. The
+ value is a case-insensitive color name taken from the CSS3 set of
+ names, defined in Section 4.3 of [W3C.REC-css3-color-20110607].
+
+ Format Definition: This property is defined by the following
+ notation:
+
+ color = "COLOR" colorparam ":" text CRLF
+ ; Value is CSS3 color name
+
+ colorparam = *(";" other-param)
+
+ Example: The following is an example of this property:
+
+ COLOR:turquoise
+
+5.10. IMAGE Property
+
+ Property Name: IMAGE
+
+ Purpose: This property specifies an image associated with the
+ calendar or a calendar component.
+
+ Value Type: URI or BINARY -- no default. The value MUST be data
+ with a media type of "image" or refer to such data.
+
+ Property Parameters: IANA, non-standard, display, inline encoding,
+ and value data type property parameters can be specified on this
+ property. The format type parameter can be specified on this
+ property and is RECOMMENDED for inline binary-encoded content
+ information.
+
+ Conformance: This property can be specified multiple times in an
+ iCalendar object or in "VEVENT", "VTODO", or "VJOURNAL" calendar
+ components.
+
+ Description: This property specifies an image for an iCalendar
+ object or a calendar component via a URI or directly with inline
+ data that can be used by calendar user agents when presenting the
+ calendar data to a user. Multiple properties MAY be used to
+ specify alternative sets of images with, for example, varying
+ media subtypes, resolutions, or sizes. When multiple properties
+ are present, calendar user agents SHOULD display only one of them,
+ picking one that provides the most appropriate image quality, or
+ display none. The "DISPLAY" parameter is used to indicate the
+ intended display mode for the image. The "ALTREP" parameter,
+
+
+
+Daboo Standards Track [Page 11]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ defined in [RFC5545], can be used to provide a "clickable" image
+ where the URI in the parameter value can be "launched" by a click
+ on the image in the calendar user agent.
+
+ Format Definition: This property is defined by the following
+ notation:
+
+ image = "IMAGE" imageparam
+ (
+ (
+ ";" "VALUE" "=" "URI"
+ ":" uri
+ ) /
+ (
+ ";" "ENCODING" "=" "BASE64"
+ ";" "VALUE" "=" "BINARY"
+ ":" binary
+ )
+ )
+ CRLF
+
+ imageparam = *(
+ ;
+ ; The following is OPTIONAL for a URI value,
+ ; RECOMMENDED for a BINARY value,
+ ; and MUST NOT occur more than once.
+ ;
+ (";" fmttypeparam) /
+ ;
+ ; The following are OPTIONAL,
+ ; and MUST NOT occur more than once.
+ ;
+ (";" altrepparam) / (";" displayparam) /
+ ;
+ ; The following is OPTIONAL,
+ ; and MAY occur more than once.
+ ;
+ (";" other-param)
+ ;
+ )
+
+ Example: The following is an example of this property:
+
+ IMAGE;VALUE=URI;DISPLAY=BADGE;FMTTYPE=image/png:h
+ ttp://example.com/images/party.png
+
+
+
+
+
+
+Daboo Standards Track [Page 12]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+5.11. CONFERENCE Property
+
+ Property Name: CONFERENCE
+
+ Purpose: This property specifies information for accessing a
+ conferencing system.
+
+ Value Type: URI -- no default.
+
+ Property Parameters: IANA, non-standard, feature, and label property
+ parameters can be specified on this property.
+
+ Conformance: This property can be specified multiple times in a
+ "VEVENT" or "VTODO" calendar component.
+
+ Description: This property specifies information for accessing a
+ conferencing system for attendees of a meeting or task. This
+ might be for a telephone-based conference number dial-in with
+ access codes included (such as a tel: URI [RFC3966] or a sip: or
+ sips: URI [RFC3261]), for a web-based video chat (such as an http:
+ or https: URI [RFC7230]), or for an instant messaging group chat
+ room (such as an xmpp: URI [RFC5122]). If a specific URI for a
+ conferencing system is not available, a data: URI [RFC2397]
+ containing a text description can be used.
+
+ A conference system can be a bidirectional communication channel
+ or a uni-directional "broadcast feed".
+
+ The "FEATURE" property parameter is used to describe the key
+ capabilities of the conference system to allow a client to choose
+ the ones that give the required level of interaction from a set of
+ multiple properties.
+
+ The "LABEL" property parameter is used to convey additional
+ details on the use of the URI. For example, the URIs or access
+ codes for the moderator and attendee of a teleconference system
+ could be different, and the "LABEL" property parameter could be
+ used to "tag" each "CONFERENCE" property to indicate which is
+ which.
+
+ The "LANGUAGE" property parameter can be used to specify the
+ language used for text values used with this property (as per
+ Section 3.2.10 of [RFC5545]).
+
+
+
+
+
+
+
+
+Daboo Standards Track [Page 13]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ Format Definition: This property is defined by the following
+ notation:
+
+ conference = "CONFERENCE" confparam ":" uri CRLF
+
+ confparam = *(
+ ;
+ ; The following is REQUIRED,
+ ; but MUST NOT occur more than once.
+ ;
+ (";" "VALUE" "=" "URI") /
+ ;
+ ; The following are OPTIONAL,
+ ; and MUST NOT occur more than once.
+ ;
+ (";" featureparam) / (";" labelparam) /
+ (";" languageparam ) /
+ ;
+ ; The following is OPTIONAL,
+ ; and MAY occur more than once.
+ ;
+ (";" other-param)
+ ;
+ )
+
+ Example: The following are examples of this property:
+
+ CONFERENCE;VALUE=URI;FEATURE=PHONE,MODERATOR;
+ LABEL=Moderator dial-in:tel:+1-412-555-0123,,,654321
+ CONFERENCE;VALUE=URI;FEATURE=PHONE;
+ LABEL=Attendee dial-in:tel:+1-412-555-0123,,,555123
+ CONFERENCE;VALUE=URI;FEATURE=PHONE;
+ LABEL=Attendee dial-in:tel:+1-888-555-0456,,,555123
+ CONFERENCE;VALUE=URI;FEATURE=CHAT;
+ LABEL=Chat room:xmpp:chat-123@conference.example.com
+ CONFERENCE;VALUE=URI;FEATURE=AUDIO,VIDEO;
+ LABEL=Attendee dial-in:https://chat.example.com/audio?id=123456
+
+6. Property Parameters
+
+6.1. DISPLAY Property Parameter
+
+ Parameter Name: DISPLAY
+
+ Purpose: To specify different ways in which an image for a calendar
+ or component can be displayed.
+
+
+
+
+
+Daboo Standards Track [Page 14]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ Format Definition: This property parameter is defined by the
+ following notation:
+
+ displayparam = "DISPLAY" "=" displayval *("," displayval)
+
+ displayval = ("BADGE" / ; image inline with the title of the
+ ; event
+ "GRAPHIC" / ; a full image replacement for the event
+ ; itself
+ "FULLSIZE" / ; an image that is used to enhance the
+ ; event
+ "THUMBNAIL" / ; a smaller variant of "FULLSIZE" to be
+ ; used when space for the image is
+ ; constrained
+ x-name / ; Experimental type
+ iana-token) ; Other IANA-registered type
+ ;
+ ; Default is BADGE
+
+ Description: This property parameter MAY be specified on "IMAGE"
+ properties. In the absence of this parameter, the default value
+ "BADGE" MUST be used. The value determines how a client ought to
+ present an image supplied in iCalendar data to the user.
+
+ Values for this parameter are registered with IANA as per
+ Section 9.3.1. New values can be added to this registry following
+ the procedure outlined in Section 8.2.1 of [RFC5545].
+
+ Servers and clients MUST handle x-name and iana-token values they
+ don't recognize by not displaying any image at all.
+
+ Example:
+
+ IMAGE;VALUE=URI;DISPLAY=BADGE,THUMBNAIL;FMTTYPE=image/png:https://exa
+ mple.com/images/weather-cloudy.png
+
+6.2. EMAIL Property Parameter
+
+ Parameter Name: EMAIL
+
+ Purpose: To specify an email address that is used to identify or
+ contact an organizer or attendee.
+
+ Format Definition: This property parameter is defined by the
+ following notation:
+
+ emailparam = "EMAIL" "=" param-value
+
+
+
+
+Daboo Standards Track [Page 15]
+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ Description: This property parameter MAY be specified on "ORGANIZER"
+ or "ATTENDEE" properties. This property can be used in situations
+ where the calendar user address value of the "ORGANIZER" and
+ "ATTENDEE" properties is not likely to be an identifier that
+ recipients of scheduling messages could use to match the calendar
+ user with, for example, an address book entry. The value of this
+ property is an email address that can easily be matched by
+ recipients. Recipients can also use this value as an alternative
+ means of contacting the calendar user via email. If a recipient's
+ calendar user agent allows the recipient to save contact
+ information based on the "ORGANIZER" or "ATTENDEE" properties,
+ those calendar user agents SHOULD use any "EMAIL" property
+ parameter value for the email address of the contact over any
+ mailto: calendar user address specified as the value of the
+ property. Calendar user agents SHOULD NOT include an "EMAIL"
+ property parameter when its value matches the calendar user
+ address specified as the value of the property.
+
+ Example:
+
+ ATTENDEE;CN=Cyrus Daboo;EMAIL=cyrus@example.com:mailto:opaque-toke
+ n-1234@example.com
+
+6.3. FEATURE Property Parameter
+
+ Parameter Name: FEATURE
+
+ Purpose: To specify a feature or features of a conference or
+ broadcast system.
+
+ Format Definition: This property parameter is defined by the
+ following notation:
+
+ featureparam = "FEATURE" "=" featuretext *("," featuretext)
+ featuretext = ("AUDIO" / ; Audio capability
+ "CHAT" / ; Chat or instant messaging
+ "FEED" / ; Blog or Atom feed
+ "MODERATOR" / ; Moderator dial-in code
+ "PHONE" / ; Phone conference
+ "SCREEN" / ; Screen sharing
+ "VIDEO" / ; Video capability
+ x-name / ; Experimental type
+ iana-token) ; Other IANA-registered type
+
+
+
+
+
+
+
+
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+
+
+ Description: This property parameter MAY be specified on the
+ "CONFERENCE" property. Multiple values can be specified. The
+ "MODERATOR" value is used to indicate that the property value is
+ specific to the owner/initiator of the conference and contains a
+ URI that "activates" the system (e.g., a "moderator" access code
+ for a phone conference system that is different from the "regular"
+ access code).
+
+ Example:
+
+ CONFERENCE;VALUE=URI;FEATURE=AUDIO:rtsp://audio.example.com/
+ event
+ CONFERENCE;VALUE=URI;FEATURE=AUDIO,VIDEO:https://video-chat.exam
+ ple.com/;group-id=1234
+
+6.4. LABEL Property Parameter
+
+ Parameter Name: LABEL
+
+ Purpose: To provide a human-readable label.
+
+ Format Definition: This property parameter is defined by the
+ following notation:
+
+ labelparam = "LABEL" "=" param-value
+
+ Description: This property parameter MAY be specified on the
+ "CONFERENCE" property. It is anticipated that other extensions to
+ iCalendar will reuse this property parameter on new properties
+ that they define. As a result, clients MUST expect to find this
+ property parameter present on many different properties. It
+ provides a human-readable label that can be presented to calendar
+ users to allow them to discriminate between properties that might
+ be similar or provide additional information for properties that
+ are not self-describing. The "LANGUAGE" property parameter can be
+ used to specify the language of the text in the parameter value
+ (as per Section 3.2.10 of [RFC5545]).
+
+ Example:
+
+ CONFERENCE;VALUE=URI;FEATURE=VIDEO;
+ LABEL="Web video chat, access code=76543";
+ :https://video-chat.example.com/;group-id=1234
+
+
+
+
+
+
+
+
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+
+
+7. Security Considerations
+
+ Several of the new properties or parameters defined by this
+ specification allow reference to "external" URIs. Care MUST be taken
+ when accessing data at external URIs as malicious content could be
+ present. Clients SHOULD ensure that suitable permission is granted
+ by calendar users before such URIs are dereferenced.
+
+ The "REFRESH-INTERVAL" property could be used by an attacker to make
+ a client carry out rapid requests to the server hosting the calendar
+ by specifying a very short duration (e.g., one second). This could
+ lead to resource consumption on the client or server and to denial-
+ of-service attacks against the server. Clients MUST ensure that they
+ throttle requests to the server to a reasonable rate. In most cases,
+ updating a public calendar once per day would suffice. If the
+ "REFRESH-INTERVAL" is any less than that, clients SHOULD warn the
+ calendar user and allow them to override it with a longer value.
+
+ The "CONFERENCE" property can include a "FEATURE" property parameter
+ with a "MODERATOR" value. In some cases, the access code used by the
+ owner/initiator of a conference might be private to an individual,
+ and clients and servers MUST ensure that such properties are not sent
+ to attendees of a scheduled component.
+
+ Both the "COLOR" and "IMAGE" properties are likely to be used by
+ calendar users to express their own personal view of the calendar
+ data. In addition, these properties could be used by attackers to
+ produce a confusing display in a calendar user agent. When such
+ properties are encountered in calendar data that has come from other
+ calendar users (e.g., via a scheduling message, "public" calendar
+ subscription, etc.), it is advisable for the client to give the
+ receiving calendar user the option to remove (or adjust) these
+ properties as the data is imported into their calendar system.
+
+ This specification changes the recommendations on how "UID" property
+ values are constructed to minimize leaking any information that might
+ be security sensitive.
+
+ Security considerations in [RFC5545] and [RFC5546] MUST also be
+ adhered to.
+
+8. Privacy Considerations
+
+ Several of the new properties or parameters defined by this
+ specification allow reference to "external" URIs. Access to those
+ URIs could be tracked, leading to loss of privacy. Clients SHOULD
+ ensure that suitable permission is granted by calendar users before
+ such URIs are dereferenced. In particular, calendar publishers
+
+
+
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+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ wishing to help protect the privacy of their subscribers MUST use
+ HTTP with Transport Layer Security [RFC7230] ("https:" URIs instead
+ of "http:" URIs) for access to calendar data or ancillary data such
+ as images.
+
+ In general, for their own privacy protection, users have to rely on
+ the privacy policies of any conferencing system being accessed via
+ the "CONFERENCE" property. It is entirely possible for such systems
+ to uniquely identify and log the activity and participation (or lack
+ thereof) of calendar users in the conference. Calendar user agents
+ SHOULD track which conferencing systems are used and warn users the
+ first time a new one is about to be used. This is particularly
+ important if the client automatically "dials in" to the conference
+ when the event start time occurs.
+
+ By giving different calendar users different values for the "REFRESH-
+ INTERVAL" property, it is possible for a publisher of calendar data
+ to uniquely identify each refresh from each calendar users' clients
+ and thereby track user activity and IP address over time. To address
+ this, clients SHOULD add or subtract some random amount of time from
+ the published "REFRESH-INTERVAL" value when doing actual refreshes.
+
+ This specification changes the recommendations on how "UID" property
+ values are constructed to minimize leaking any information that might
+ be privacy sensitive.
+
+ Privacy considerations in [RFC5545] and [RFC5546] MUST also be
+ adhered to.
+
+9. IANA Considerations
+
+9.1. Property Registrations
+
+ This document defines the following new iCalendar properties. IANA
+ has registered the new properties in the "Properties" registry
+ defined in Section 8.3.2 of [RFC5545]. IANA has also added a
+ reference to this document where the properties originally defined in
+ RFC 5545 have been updated by this document.
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ +------------------+---------+--------------------------------------+
+ | Property | Status | Reference |
+ +------------------+---------+--------------------------------------+
+ | NAME | Current | RFC 7986, Section 5.1 |
+ | DESCRIPTION | Current | RFC 5545, Section 3.8.1.5; RFC 7986, |
+ | | | Section 5.2 |
+ | UID | Current | RFC 5545, Section 3.8.4.7; RFC 7986, |
+ | | | Section 5.3 |
+ | LAST-MODIFIED | Current | RFC 5545, Section 3.8.7.3 RFC 7986, |
+ | | | Section 5.4 |
+ | URL | Current | RFC 5545, Section 3.8.4.6; RFC 7986, |
+ | | | Section 5.5 |
+ | CATEGORIES | Current | RFC 5545, Section 3.8.1.2; RFC 7986, |
+ | | | Section 5.6 |
+ | REFRESH-INTERVAL | Current | RFC 7986, Section 5.7 |
+ | SOURCE | Current | RFC 7986, Section 5.8 |
+ | COLOR | Current | RFC 7986, Section 5.9 |
+ | IMAGE | Current | RFC 7986, Section 5.10 |
+ | CONFERENCE | Current | RFC 7986, Section 5.11 |
+ +------------------+---------+--------------------------------------+
+
+9.2. Parameter Registrations
+
+ This document defines the following new iCalendar property
+ parameters. IANA has registered these in the "Parameters" registry
+ defined in Section 8.3.3 of [RFC5545].
+
+ +--------------------+---------+-----------------------+
+ | Property Parameter | Status | Reference |
+ +--------------------+---------+-----------------------+
+ | DISPLAY | Current | RFC 7986, Section 6.1 |
+ | EMAIL | Current | RFC 7986, Section 6.2 |
+ | FEATURE | Current | RFC 7986, Section 6.3 |
+ | LABEL | Current | RFC 7986, Section 6.4 |
+ +--------------------+---------+-----------------------+
+
+9.3. Property Parameter Value Registries
+
+ IANA has created two new registries for iCalendar elements: the
+ "Display Types" registry and the "Feature Types" registry.
+ Additional codes MAY be used, provided the process and template
+ described in Sections 8.2.1 and 8.2.6 of [RFC5545] are used to
+ register them.
+
+
+
+
+
+
+
+
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+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+9.3.1. Display Types Registry
+
+ The following table has been used to initialize the "Display Types"
+ registry.
+
+ +--------------+---------+-----------------------+
+ | Display Type | Status | Reference |
+ +--------------+---------+-----------------------+
+ | BADGE | Current | RFC 7986, Section 6.1 |
+ | GRAPHIC | Current | RFC 7986, Section 6.1 |
+ | FULLSIZE | Current | RFC 7986, Section 6.1 |
+ | THUMBNAIL | Current | RFC 7986, Section 6.1 |
+ +--------------+---------+-----------------------+
+
+9.3.2. Feature Types Registry
+
+ The following table has been used to initialize the "Feature Types"
+ registry.
+
+ +--------------+---------+-----------------------+
+ | Feature Type | Status | Reference |
+ +--------------+---------+-----------------------+
+ | AUDIO | Current | RFC 7986, Section 6.3 |
+ | CHAT | Current | RFC 7986, Section 6.3 |
+ | FEED | Current | RFC 7986, Section 6.3 |
+ | MODERATOR | Current | RFC 7986, Section 6.3 |
+ | PHONE | Current | RFC 7986, Section 6.3 |
+ | SCREEN | Current | RFC 7986, Section 6.3 |
+ | VIDEO | Current | RFC 7986, Section 6.3 |
+ +--------------+---------+-----------------------+
+
+10. References
+
+10.1. 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,
+ <http://www.rfc-editor.org/info/rfc2119>.
+
+ [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
+ Unique IDentifier (UUID) URN Namespace", RFC 4122,
+ DOI 10.17487/RFC4122, July 2005,
+ <http://www.rfc-editor.org/info/rfc4122>.
+
+
+
+
+
+
+
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+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+ [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", STD 68, RFC 5234,
+ DOI 10.17487/RFC5234, January 2008,
+ <http://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,
+ <http://www.rfc-editor.org/info/rfc5545>.
+
+ [RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent
+ Interoperability Protocol (iTIP)", RFC 5546,
+ DOI 10.17487/RFC5546, December 2009,
+ <http://www.rfc-editor.org/info/rfc5546>.
+
+ [W3C.REC-css3-color-20110607]
+ Celik, T., Lilley, C., and D. Baron, "CSS Color Module
+ Level 3", World Wide Web Consortium Recommendation
+ REC-css3-color-20110607, June 2011,
+ <https://www.w3.org/TR/2011/REC-css3-color-20110607>.
+
+10.2. Informative References
+
+ [RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397,
+ DOI 10.17487/RFC2397, August 1998,
+ <http://www.rfc-editor.org/info/rfc2397>.
+
+ [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
+ A., Peterson, J., Sparks, R., Handley, M., and E.
+ Schooler, "SIP: Session Initiation Protocol", RFC 3261,
+ DOI 10.17487/RFC3261, June 2002,
+ <http://www.rfc-editor.org/info/rfc3261>.
+
+ [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
+ RFC 3966, DOI 10.17487/RFC3966, December 2004,
+ <http://www.rfc-editor.org/info/rfc3966>.
+
+ [RFC5122] Saint-Andre, P., "Internationalized Resource Identifiers
+ (IRIs) and Uniform Resource Identifiers (URIs) for the
+ Extensible Messaging and Presence Protocol (XMPP)",
+ RFC 5122, DOI 10.17487/RFC5122, February 2008,
+ <http://www.rfc-editor.org/info/rfc5122>.
+
+ [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
+ Protocol (HTTP/1.1): Message Syntax and Routing",
+ RFC 7230, DOI 10.17487/RFC7230, June 2014,
+ <http://www.rfc-editor.org/info/rfc7230>.
+
+
+
+
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+
+RFC 7986 iCalendar Property Extensions October 2016
+
+
+Acknowledgments
+
+ Thanks to the following individuals for feedback: Bernard
+ Desruisseaux, Mike Douglass, Lucia Fedorova, Ken Murchison, Arnaud
+ Quillaud, and Dave Thewlis.
+
+ This specification came about via discussions at the Calendaring and
+ Scheduling Consortium.
+
+Author's Address
+
+ Cyrus Daboo
+ Apple Inc.
+ 1 Infinite Loop
+ Cupertino, CA 95014
+ United States of America
+
+ Email: cyrus@daboo.name
+ URI: http://www.apple.com/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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