Network Working Group C. Daboo
Internet-Draft Apple Inc.
Intended status: Standards Track July 12, 2010
Expires: January 13, 2011
New Properties for iCalendar
draft-daboo-icalendar-extensions-01
Abstract
This document defines a set of new properties for iCalendar data.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 13, 2011.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Modifications to Calendar Components . . . . . . . . . . . . . 3
4. Calendar Properties . . . . . . . . . . . . . . . . . . . . . 4
4.1. CALENDAR-NAME Property . . . . . . . . . . . . . . . . . . 5
4.2. CALENDAR-DESCRIPTION Property . . . . . . . . . . . . . . 6
4.3. CALENDAR-UID Property . . . . . . . . . . . . . . . . . . 7
4.4. CALENDAR-URL Property . . . . . . . . . . . . . . . . . . 7
4.5. CALENDAR-TZID Property . . . . . . . . . . . . . . . . . . 8
4.6. CALENDAR-REFRESH-INTERVAL Property . . . . . . . . . . . . 9
4.7. CALENDAR-COLOR Property . . . . . . . . . . . . . . . . . 10
4.8. CALENDAR-IMAGE Property . . . . . . . . . . . . . . . . . 10
5. Component Properties . . . . . . . . . . . . . . . . . . . . . 12
5.1. IMAGE Property . . . . . . . . . . . . . . . . . . . . . . 12
6. Property Parameters . . . . . . . . . . . . . . . . . . . . . 14
6.1. DISPLAY Property Parameter . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8.1. Property Registrations . . . . . . . . . . . . . . . . . . 15
8.2. Parameter Registrations . . . . . . . . . . . . . . . . . 16
8.3. Display Types Registry . . . . . . . . . . . . . . . . . . 16
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Appendix A. Change History (To be removed by RFC Editor
before publication) . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
The iCalendar [RFC5545] data format is used to represent calendar
data and is used with 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 collates 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 been recently
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. Modifications to Calendar Components
The following changes to the syntax defined in iCalendar [RFC5545]
are made here. New elements are defined in subsequent sections.
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calprops /= *(
;
; The following are OPTIONAL,
; but MUST NOT occur more than once.
;
caluid / calurl / caltzid /
calrefresh / calcolor /
;
; The following are OPTIONAL,
; and MAY occur more than once.
;
calname / caldescription / calimg
;
)
eventprop /= *(
;
; The following are OPTIONAL,
; and MAY occur more than once.
;
image
;
)
todoprop /= *(
;
; The following are OPTIONAL,
; and MAY occur more than once.
;
image
;
)
jourprop /= *(
;
; The following are OPTIONAL,
; and MAY occur more than once.
;
image
;
)
4. Calendar Properties
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4.1. CALENDAR-NAME Property
Property Name: CALENDAR-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 (a short, one-
line description) 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.
Format Definition: This property is defined by the following
notation:
calname = "CALENDAR-NAME" calnameparam ":" text CRLF
calnameparam = *(
;
; 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:
CALENDAR-NAME:Company Vacation Days
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4.2. CALENDAR-DESCRIPTION Property
Property Name: CALENDAR-DESCRIPTION
Purpose: This property specifies the description 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
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.
Format Definition: This property is defined by the following
notation:
caldesc = "CALENDAR-DESCRIPTION" caldescparam ":" text
CRLF
caldescparam = *(
;
; 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:
CALENDAR-DESCRIPTION:This calendar contains all the \
official vacation days of our company.\nThese repre\
sent paid time-off - make sure you have fun, we'll \
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be working you hard on the other days!
4.3. CALENDAR-UID Property
Property Name: CALENDAR-UID
Purpose: This property specifies the persistent, globally unique
identifier for the calendar.
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.
Description: The value of this property MUST be a globally unique
identifier. The generator of the property MUST guarantee that the
value is unique. This can be done following the recommendations
in Section 3.8.4.7 of [RFC5545]. Implementations MUST be able to
receive and persist values of at least 255 octets for this
property, but they MUST NOT truncate values in the middle of a
UTF-8 multi-octet sequence.
Format Definition: This property is defined by the following
notation:
caluid = "CALENDAR-UID" caluidparam ":" text CRLF
caluidparam = *(";" other-param)
Example: The following is an example of this property:
CALENDAR-UID:19960401T080045Z-4000F192713-0052@example.com
4.4. CALENDAR-URL Property
Property Name: CALENDAR-URL
Purpose: This property specifies a URL from where the calendar data
was retrieved or where it can be refreshed.
Value Type: URI
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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 URL identifying the source of
the calendar data and a location from where updates can be
retrieved.
Format Definition: This property is defined by the following
notation:
calurl = "CALENDAR-URL" calurlparam ":" url CRLF
calurlparam = *(";" other-param)
Example: The following is an example of this property:
CALENDAR-URL:http://calendars.example.com/holidays/canada.ics
4.5. CALENDAR-TZID Property
Property Name: CALENDAR-TZID
Purpose: This property specifies the default time zone identifier
for the calendar.
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.
Description: This property specifies a time zone identifier that
represents the default timezone for which floating time or all-day
events in the iCalendar object can be assumed to be relative to.
It can also be used to choose an initial time zone for use when
creating new components in the iCalendar object. A "VTIMEZONE"
component having a "TZID" property matching the value specified in
this property MUST be present in the iCalendar object.
Format Definition: This property is defined by the following
notation:
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caltzid = "CALENDAR-TZID" caltzidparam ":" [tzidprefix]
text CRLF
caltzidparam = *(";" other-param)
Example: The following is an example of this property:
CALENDAR-TZID:America/New_York
4.6. CALENDAR-REFRESH-INTERVAL Property
Property Name: CALENDAR-REFRESH-INTERVAL
Purpose: This property specifies a suggested interval for polling
for changes of the calendar data from the original source of that
data.
Value Type: DURATION
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 polling interval for checking for updates to the
calendar data. The value of this property SHOULD be used by
calendar user agents as the polling interval for calendar data
updates.
Format Definition: This property is defined by the following
notation:
calrefesh = "CALENDAR-REFRESH-INTERVAL" calrefreshparam
":" dur-value CRLF
;consisting of a positive duration of time.
calrefeshparam = *(";" other-param)
Example: The following is an example of this property:
CALENDAR-REFRESH-INTERVAL:P1W
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4.7. CALENDAR-COLOR Property
Property Name: CALENDAR-COLOR
Purpose: This property specifies a color used for displaying the
calendar data.
Value Type: INTEGER. The value MUST be three SEMICOLON-separated
INTEGER values.
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 color that client MAY use
when presenting the calendar data to a user. Typically this would
appear as the "background" color of events or tasks. The value
MUST be an RGB value with integer value components in the range
0..255
Format Definition: This property is defined by the following
notation:
calcolor = "CALENDAR-COLOR" calcolorparam ":"
calcolorvalue CRLF
calcolorparam = *(";" other-param)
calcolorvalue = integer ";" integer ";" integer
; Red, green, and blue values in the range
; 0 - 255.
Example: The following is an example of this property:
CALENDAR-COLOR:255;0;255
4.8. CALENDAR-IMAGE Property
Property Name: CALENDAR-IMAGE
Purpose: This property specifies an image associated with the
calendar.
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Value Type: The default value type for this property is URI. The
value type can also be set to BINARY to indicate inline binary
encoded content information. The value MUST refer to or be data
with a media type of "image".
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.
Description: This property specifies an image for an iCalendar
object 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.
Format Definition: This property is defined by the following
notation:
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calimg = "CALENDAR-IMAGE" calimgparam ( ":" uri ) /
(
";" "ENCODING" "=" "BASE64"
";" "VALUE" "=" "BINARY"
":" binary
)
CRLF
calimgparam = *(
;
; The following is OPTIONAL for a URI value,
; RECOMMENDED for a BINARY value,
; and MUST NOT occur more than once.
;
(";" fmttypeparam) /
;
; The following is OPTIONAL,
; and MOST NOT occur more than once.
;
(";" displayparam)
;
; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example: The following is an example of this property:
CALENDAR-IMAGE;DISPLAY=BADGE;FMTTYPE=image/png:http://ex
ample.com/images/holiday.png
5. Component Properties
5.1. IMAGE Property
Property Name: IMAGE
Purpose: This property specifies an image associated with a calendar
component.
Value Type: The default value type for this property is URI. The
value type can also be set to BINARY to indicate inline binary
encoded content information. The value MUST refer to or be data
with a media type of "image".
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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 a
"VEVENT", "VTODO", or "VJOURNAL" calendar component.
Description: This property specifies an image for 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.
Format Definition: This property is defined by the following
notation:
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image = "IMAGE" imageparam ( ":" 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 is OPTIONAL,
; and MOST NOT occur more than once.
;
(";" displayparam)
;
; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example: The following is an example of this property:
IMAGE;DISPLAY=BACKGROUND;FMTTYPE=image/png:htt
p://example.com/images/party.png
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.
Format Definition: This property parameter is defined by the
following notation:
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displayparam = "DISPLAY" "="
("BADGE" / ; A small "badge" image
"BACKGROUND" / ; Use as a background image
"OVERLAY" / ; Use as an overlay image
"BANNER" / ; Use as a "banner" across the top
x-name / ; Experimental type
iana-token) ; Other IANA registered type
;
; Default is BADGE
Description: This property parameter MAY be specified on "CALENDAR-
IMAGE" or "IMAGE" properties. In the absence of this parameter,
the value "BADGE" MUST be used for the default behavior. 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 8.3. 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;DISPLAY=BANNER;FMTTYPE=image/png:htt
p://example.com/images/weather-cloudy.png
7. Security Considerations
TODO:Perhaps discuss issues with image processing related buffer
overflows, accessing external URLs (privacy), etc.
8. IANA Considerations
8.1. Property Registrations
This document defines the following new iCalendar properties to be
added to the registry defined in Section 8.2.3 of [RFC5545]:
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+---------------------------+---------+----------------------+
| Property | Status | Reference |
+---------------------------+---------+----------------------+
| CALENDAR-NAME | Current | RFCXXXX, Section 4.1 |
| CALENDAR-DESCRIPTION | Current | RFCXXXX, Section 4.2 |
| CALENDAR-UID | Current | RFCXXXX, Section 4.3 |
| CALENDAR-URL | Current | RFCXXXX, Section 4.4 |
| CALENDAR-TZID | Current | RFCXXXX, Section 4.5 |
| CALENDAR-REFRESH-INTERVAL | Current | RFCXXXX, Section 4.6 |
| CALENDAR-COLOR | Current | RFCXXXX, Section 4.7 |
| CALENDAR-IMAGE | Current | RFCXXXX, Section 4.8 |
| IMAGE | Current | RFCXXXX, Section 5.1 |
+---------------------------+---------+----------------------+
8.2. Parameter Registrations
This document defines the following new iCalendar property parameters
to be added to the registry defined in Section 8.2.4 of [RFC5545]:
+--------------------+---------+----------------------+
| Property Parameter | Status | Reference |
+--------------------+---------+----------------------+
| DISPLAY | Current | RFCXXXX, Section 6.1 |
+--------------------+---------+----------------------+
8.3. Display Types Registry
This document defines the following new iCalendar value registry as
per Section 8.2.6 of [RFC5545]:
+--------------+---------+----------------------+
| Display Type | Status | Reference |
+--------------+---------+----------------------+
| BADGE | Current | RFCXXXX, Section 6.1 |
| BACKGROUND | Current | RFCXXXX, Section 6.1 |
| OVERLAY | Current | RFCXXXX, Section 6.1 |
| BANNER | Current | RFCXXXX, Section 6.1 |
+--------------+---------+----------------------+
9. Acknowledgments
This specification came about via discussions at the Calendaring and
Scheduling Consortium.
10. References
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10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling
Core Object Specification (iCalendar)", RFC 5545,
September 2009.
10.2. Informative References
[RFC5546] Daboo, C., "iCalendar Transport-Independent
Interoperability Protocol (iTIP)", RFC 5546,
December 2009.
Appendix A. Change History (To be removed by RFC Editor before
publication)
Changes in -01:
1. Fixed DISPLAY parameter handling of x- and iana tokens to state
that clients ignore the image if the token is not recognized.
2. Allow language variants for CALENDAR-NAME and CALENDAR-
DESCRIPTION.
3. Added registry for DISPLAY values.
Author's Address
Cyrus Daboo
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
Email: cyrus@daboo.name
URI: http://www.apple.com/
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