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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
+
+
+
+
+
+
+
+
+Daboo                        Standards Track                   [Page 16]
+
+RFC 7986              iCalendar Property Extensions         October 2016
+
+
+   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
+
+
+
+
+
+
+
+
+Daboo                        Standards Track                   [Page 17]
+
+RFC 7986              iCalendar Property Extensions         October 2016
+
+
+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
+
+
+
+Daboo                        Standards Track                   [Page 18]
+
+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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Daboo                        Standards Track                   [Page 19]
+
+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.
+
+
+
+
+
+
+
+
+Daboo                        Standards Track                   [Page 20]
+
+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>.
+
+
+
+
+
+
+
+Daboo                        Standards Track                   [Page 21]
+
+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>.
+
+
+
+
+Daboo                        Standards Track                   [Page 22]
+
+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/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Daboo                        Standards Track                   [Page 23]
+