draft-ietf-calext-extensions-03.txt   draft-ietf-calext-extensions-04.txt 
Network Working Group C. Daboo Network Working Group C. Daboo
Internet-Draft Apple Inc. Internet-Draft Apple Inc.
Intended status: Standards Track June 3, 2016 Updates: 5545 (if approved) June 28, 2016
Expires: December 5, 2016 Intended status: Standards Track
Expires: December 30, 2016
New Properties for iCalendar New Properties for iCalendar
draft-ietf-calext-extensions-03 draft-ietf-calext-extensions-04
Abstract Abstract
This document defines a set of new properties for iCalendar data as This document defines a set of new properties for iCalendar data as
well as extending the use of some existing properties to the entire well as extending the use of some existing properties to the entire
iCalendar object. iCalendar object.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 32 skipping to change at page 1, line 33
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 5, 2016. This Internet-Draft will expire on December 30, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 29 skipping to change at page 2, line 29
5.8. SOURCE Property . . . . . . . . . . . . . . . . . . . . . 9 5.8. SOURCE Property . . . . . . . . . . . . . . . . . . . . . 9
5.9. COLOR Property . . . . . . . . . . . . . . . . . . . . . 9 5.9. COLOR Property . . . . . . . . . . . . . . . . . . . . . 9
5.10. IMAGE Property . . . . . . . . . . . . . . . . . . . . . 10 5.10. IMAGE Property . . . . . . . . . . . . . . . . . . . . . 10
5.11. CONFERENCE Property . . . . . . . . . . . . . . . . . . . 12 5.11. CONFERENCE Property . . . . . . . . . . . . . . . . . . . 12
6. Property Parameters . . . . . . . . . . . . . . . . . . . . . 13 6. Property Parameters . . . . . . . . . . . . . . . . . . . . . 13
6.1. DISPLAY Property Parameter . . . . . . . . . . . . . . . 13 6.1. DISPLAY Property Parameter . . . . . . . . . . . . . . . 13
6.2. EMAIL Property Parameter . . . . . . . . . . . . . . . . 14 6.2. EMAIL Property Parameter . . . . . . . . . . . . . . . . 14
6.3. FEATURE Property Parameter . . . . . . . . . . . . . . . 15 6.3. FEATURE Property Parameter . . . . . . . . . . . . . . . 15
6.4. LABEL Property Parameter . . . . . . . . . . . . . . . . 16 6.4. LABEL Property Parameter . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 17
8.1. Property Registrations . . . . . . . . . . . . . . . . . 17 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8.2. Parameter Registrations . . . . . . . . . . . . . . . . . 17 9.1. Property Registrations . . . . . . . . . . . . . . . . . 17
8.3. Display Types Registry . . . . . . . . . . . . . . . . . 18 9.2. Parameter Registrations . . . . . . . . . . . . . . . . . 18
8.4. Feature Types Registry . . . . . . . . . . . . . . . . . 18 9.3. Display Types Registry . . . . . . . . . . . . . . . . . 18
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 9.4. Feature Types Registry . . . . . . . . . . . . . . . . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . 18 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 19 11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. Change History (To be removed by RFC Editor before Appendix A. Change History (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 19 publication) . . . . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 22 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction 1. Introduction
The iCalendar [RFC5545] data format is used to represent calendar The iCalendar [RFC5545] data format is used to represent calendar
data and is used with iTIP [RFC5546] to handle scheduling operations data and is used with iTIP [RFC5546] to handle scheduling operations
between calendar users. iCalendar is in widespread use, and in between calendar users. iCalendar is in widespread use, and in
accordance with provisions in that specification, extension elements accordance with provisions in that specification, extension elements
have been added by various vendors to the data format in order to have been added by various vendors to the data format in order to
support and enhance capabilities. This specification collects a support and enhance capabilities. This specification collects a
number of these ad-hoc extensions and uses the new IANA registry number of these ad-hoc extensions and uses the new IANA registry
skipping to change at page 4, line 28 skipping to change at page 4, line 29
eventprop =/ *( eventprop =/ *(
; ;
; The following are OPTIONAL, ; The following are OPTIONAL,
; but MUST NOT occur more than once. ; but MUST NOT occur more than once.
; ;
color / color /
; ;
; The following are OPTIONAL, ; The following are OPTIONAL,
; and MAY occur more than once. ; and MAY occur more than once.
; ;
image conference / image
; ;
) )
todoprop =/ *( todoprop =/ *(
; ;
; The following are OPTIONAL, ; The following are OPTIONAL,
; but MUST NOT occur more than once. ; but MUST NOT occur more than once.
; ;
color / color /
; ;
; The following are OPTIONAL, ; The following are OPTIONAL,
; and MAY occur more than once. ; and MAY occur more than once.
; ;
image conference / image
; ;
) )
jourprop =/ *( jourprop =/ *(
; ;
; The following are OPTIONAL, ; The following are OPTIONAL,
; but MUST NOT occur more than once. ; but MUST NOT occur more than once.
; ;
color / color /
; ;
; The following are OPTIONAL, ; The following are OPTIONAL,
; and MAY occur more than once. ; and MAY occur more than once.
; ;
image conference / image
; ;
) )
5. Properties 5. Properties
5.1. NAME Property 5.1. NAME Property
Property Name: NAME Property Name: NAME
Purpose: This property specifies the name of the calendar. Purpose: This property specifies the name of the calendar.
skipping to change at page 6, line 29 skipping to change at page 6, line 29
) )
Example: The following is an example of this property: Example: The following is an example of this property:
NAME:Company Vacation Days NAME:Company Vacation Days
5.2. DESCRIPTION Property 5.2. DESCRIPTION Property
This specification modifies the definition of the "DESCRIPTION" This specification modifies the definition of the "DESCRIPTION"
property to allow it to be defined on an iCalendar object. The property to allow it to be defined on an iCalendar object. The
following additions are made to the definition of this property. 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. Purpose: This property specifies the description of the calendar.
Conformance: This property can be specified multiple times in an Conformance: This property can be specified multiple times in an
iCalendar object. However, each property MUST represent the iCalendar object. However, each property MUST represent the
description of the calendar in a different language. description of the calendar in a different language.
Description: This property is used to specify a lengthy textual Description: This property is used to specify a lengthy textual
description of the iCalendar object that can be used by calendar description of the iCalendar object that can be used by calendar
user agents when describing the nature of the calendar data to a user agents when describing the nature of the calendar data to a
user. Whilst a calendar only has a single description, multiple user. Whilst a calendar only has a single description, multiple
language variants can be specified by including this property language variants can be specified by including this property
multiple times with different "LANGUAGE" parameter values on each. multiple times with different "LANGUAGE" parameter values on each.
5.3. UID Property 5.3. UID Property
This specification modifies the definition of the "UID" property to This specification modifies the definition of the "UID" property to
allow it to be defined on an iCalendar object. The following allow it to be defined on an iCalendar object. The following
additions are made to the definition of this property. 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 Purpose: This property specifies the persistent, globally unique
identifier for the iCalendar object. This can be used, for identifier for the iCalendar object. This can be used, for
example, to identify duplicate calendar streams that a client may example, to identify duplicate calendar streams that a client may
have been given access to. It can be used in conjunction with the have been given access to. It can be used in conjunction with the
"LAST-MODIFIED" property also specified on the "VCALENDAR" object, "LAST-MODIFIED" property also specified on the "VCALENDAR" object,
to identify the most recent version of a calendar. to identify the most recent version of a calendar.
Conformance: This property can be specified once in an iCalendar Conformance: This property can be specified once in an iCalendar
object. object.
5.4. LAST-MODIFIED Property 5.4. LAST-MODIFIED Property
This specification modifies the definition of the "LAST-MODIFIED" This specification modifies the definition of the "LAST-MODIFIED"
property to allow it to be defined on an iCalendar object. The property to allow it to be defined on an iCalendar object. The
following additions are made to the definition of this property. 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 Purpose: This property specifies the date and time that the
information associated with the calendar was last revised. information associated with the calendar was last revised.
Conformance: This property can be specified once in an iCalendar Conformance: This property can be specified once in an iCalendar
object. object.
5.5. URL Property 5.5. URL Property
This specification modifies the definition of the "URL" property to This specification modifies the definition of the "URL" property to
allow it to be defined on an iCalendar object. The following allow it to be defined on an iCalendar object. The following
additions are made to the definition of this property. 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 Purpose: This property may be used to convey a location where a more
dynamic rendition of the calendar information can be found. dynamic rendition of the calendar information can be found.
Conformance: This property can be specified once in an iCalendar Conformance: This property can be specified once in an iCalendar
object. object.
5.6. CATEGORIES Property 5.6. CATEGORIES Property
This specification modifies the definition of the "CATEGORIES" This specification modifies the definition of the "CATEGORIES"
property to allow it to be defined on an iCalendar object. The property to allow it to be defined on an iCalendar object. The
following additions are made to the definition of this property. 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 Purpose: This property defines the categories for an entire
calendar. calendar.
Conformance: This property can be specified multiple times in an Conformance: This property can be specified multiple times in an
iCalendar object. iCalendar object.
Description: When multiple properties are present, the set of Description: When multiple properties are present, the set of
categories that apply to the iCalendar object are the union of all categories that apply to the iCalendar object are the union of all
the categories listed in each property value. the categories listed in each property value.
skipping to change at page 14, line 28 skipping to change at page 14, line 28
; ;
; Default is BADGE ; Default is BADGE
Description: This property parameter MAY be specified on "IMAGE" Description: This property parameter MAY be specified on "IMAGE"
properties. In the absence of this parameter, the value "BADGE" properties. In the absence of this parameter, the value "BADGE"
MUST be used for the default behavior. The value determines how a MUST be used for the default behavior. The value determines how a
client ought to present an image supplied in iCalendar data to the client ought to present an image supplied in iCalendar data to the
user. user.
Values for this parameter are registered with IANA as per Values for this parameter are registered with IANA as per
Section 8.3. New values can be added to this registry following Section 9.3. New values can be added to this registry following
the procedure outlined in Section 8.2.1 of [RFC5545]. the procedure outlined in Section 8.2.1 of [RFC5545].
Servers and clients MUST handle x-name and iana-token values they Servers and clients MUST handle x-name and iana-token values they
don't recognize by not displaying any image at all. don't recognize by not displaying any image at all.
Example: Example:
IMAGE;VALUE=URI;DISPLAY=BADGE,THUMBNAIL;FMTTYPE=image/png:https://exa IMAGE;VALUE=URI;DISPLAY=BADGE,THUMBNAIL;FMTTYPE=image/png:https://exa
mple.com/images/weather-cloudy.png mple.com/images/weather-cloudy.png
skipping to change at page 16, line 46 skipping to change at page 16, line 46
CONFERENCE;VALUE=URI;FEATURE=VIDEO; CONFERENCE;VALUE=URI;FEATURE=VIDEO;
LABEL="Web video chat, access code=76543"; LABEL="Web video chat, access code=76543";
:https://video-chat.example.com/;group-id=1234 :https://video-chat.example.com/;group-id=1234
7. Security Considerations 7. Security Considerations
Several of the new properties or parameters defined by this Several of the new properties or parameters defined by this
specification allow reference to "external" URIs. Care MUST be taken specification allow reference to "external" URIs. Care MUST be taken
when accessing data at external URIs as malicious content could be when accessing data at external URIs as malicious content could be
present. In addition, access to those URIs could be tracked, leading present. Clients SHOULD ensure that suitable permission is granted
to loss of privacy. 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 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 The "CONFERENCE" property can include a "FEATURE" property parameter
with a "MODERATOR" value. In some cases the access code used by the 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 owner/initiator of a conference might be private to an individual and
clients and servers MUST ensure that such properties are not sent to clients and servers MUST ensure that such properties are not sent to
attendees of a scheduled component, or sharees of a shared component. attendees of a scheduled component, or sharees of a shared component.
8. IANA Considerations 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, shared calendar 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.
8.1. Property Registrations 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.
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 to be This document defines the following new iCalendar properties to be
added to the registry defined in Section 8.2.3 of [RFC5545]: added to the registry defined in Section 8.3.2 of [RFC5545]:
+------------------+---------+--------------------------------------+ +------------------+---------+--------------------------------------+
| Property | Status | Reference | | Property | Status | Reference |
+------------------+---------+--------------------------------------+ +------------------+---------+--------------------------------------+
| NAME | Current | RFCXXXX, Section 5.1 | | NAME | Current | RFCXXXX, Section 5.1 |
| DESCRIPTION | Current | RFC5545 Section 3.8.1.5, RFCXXXX, | | DESCRIPTION | Current | RFC5545 Section 3.8.1.5, RFCXXXX, |
| | | Section 5.2 | | | | Section 5.2 |
| UID | Current | RFC5545 Section 3.8.4.7, RFCXXXX, | | UID | Current | RFC5545 Section 3.8.4.7, RFCXXXX, |
| | | Section 5.3 | | | | Section 5.3 |
| LAST-MODIFIED | Current | RFC5545 Section 3.8.7.3, RFCXXXX, | | LAST-MODIFIED | Current | RFC5545 Section 3.8.7.3, RFCXXXX, |
skipping to change at page 17, line 35 skipping to change at page 18, line 26
| | | Section 5.5 | | | | Section 5.5 |
| CATEGORIES | Current | RFC5545 Section 3.8.1.2, RFCXXXX, | | CATEGORIES | Current | RFC5545 Section 3.8.1.2, RFCXXXX, |
| | | Section 5.6 | | | | Section 5.6 |
| REFRESH-INTERVAL | Current | RFCXXXX, Section 5.7 | | REFRESH-INTERVAL | Current | RFCXXXX, Section 5.7 |
| SOURCE | Current | RFCXXXX, Section 5.8 | | SOURCE | Current | RFCXXXX, Section 5.8 |
| COLOR | Current | RFCXXXX, Section 5.9 | | COLOR | Current | RFCXXXX, Section 5.9 |
| IMAGE | Current | RFCXXXX, Section 5.10 | | IMAGE | Current | RFCXXXX, Section 5.10 |
| CONFERENCE | Current | RFCXXXX, Section 5.11 | | CONFERENCE | Current | RFCXXXX, Section 5.11 |
+------------------+---------+--------------------------------------+ +------------------+---------+--------------------------------------+
8.2. Parameter Registrations 9.2. Parameter Registrations
This document defines the following new iCalendar property parameters This document defines the following new iCalendar property parameters
to be added to the registry defined in Section 8.2.4 of [RFC5545]: to be added to the registry defined in Section 8.3.3 of [RFC5545]:
+--------------------+---------+----------------------+ +--------------------+---------+----------------------+
| Property Parameter | Status | Reference | | Property Parameter | Status | Reference |
+--------------------+---------+----------------------+ +--------------------+---------+----------------------+
| DISPLAY | Current | RFCXXXX, Section 6.1 | | DISPLAY | Current | RFCXXXX, Section 6.1 |
| EMAIL | Current | RFCXXXX, Section 6.2 | | EMAIL | Current | RFCXXXX, Section 6.2 |
| FEATURE | Current | RFCXXXX, Section 6.3 | | FEATURE | Current | RFCXXXX, Section 6.3 |
| LABEL | Current | RFCXXXX, Section 6.4 | | LABEL | Current | RFCXXXX, Section 6.4 |
+--------------------+---------+----------------------+ +--------------------+---------+----------------------+
8.3. Display Types Registry 9.3. Display Types Registry
This document defines the following new iCalendar value registry as This document defines the following new iCalendar value registry as
per Section 8.2.6 of [RFC5545]: per Section 8.2.6 of [RFC5545]:
+--------------+---------+----------------------+ +--------------+---------+----------------------+
| Display Type | Status | Reference | | Display Type | Status | Reference |
+--------------+---------+----------------------+ +--------------+---------+----------------------+
| BADGE | Current | RFCXXXX, Section 6.1 | | BADGE | Current | RFCXXXX, Section 6.1 |
| GRAPHIC | Current | RFCXXXX, Section 6.1 | | GRAPHIC | Current | RFCXXXX, Section 6.1 |
| FULLSIZE | Current | RFCXXXX, Section 6.1 | | FULLSIZE | Current | RFCXXXX, Section 6.1 |
| THUMBNAIL | Current | RFCXXXX, Section 6.1 | | THUMBNAIL | Current | RFCXXXX, Section 6.1 |
+--------------+---------+----------------------+ +--------------+---------+----------------------+
8.4. Feature Types Registry 9.4. Feature Types Registry
This document defines the following new iCalendar value registry as This document defines the following new iCalendar value registry as
per Section 8.2.6 of [RFC5545]: per Section 8.2.6 of [RFC5545]:
+--------------+---------+----------------------+ +--------------+---------+----------------------+
| Feature Type | Status | Reference | | Feature Type | Status | Reference |
+--------------+---------+----------------------+ +--------------+---------+----------------------+
| AUDIO | Current | RFCXXXX, Section 6.3 | | AUDIO | Current | RFCXXXX, Section 6.3 |
| CHAT | Current | RFCXXXX, Section 6.3 | | CHAT | Current | RFCXXXX, Section 6.3 |
| FEED | Current | RFCXXXX, Section 6.3 | | FEED | Current | RFCXXXX, Section 6.3 |
| MODERATOR | Current | RFCXXXX, Section 6.3 | | MODERATOR | Current | RFCXXXX, Section 6.3 |
| PHONE | Current | RFCXXXX, Section 6.3 | | PHONE | Current | RFCXXXX, Section 6.3 |
| SCREEN | Current | RFCXXXX, Section 6.3 | | SCREEN | Current | RFCXXXX, Section 6.3 |
| VIDEO | Current | RFCXXXX, Section 6.3 | | VIDEO | Current | RFCXXXX, Section 6.3 |
+--------------+---------+----------------------+ +--------------+---------+----------------------+
9. Acknowledgments 10. Acknowledgments
Thanks to the following for feedback: Bernard Desruisseaux, Mike Thanks to the following for feedback: Bernard Desruisseaux, Mike
Douglass, Lucia Fedorova, Ken Murchison, Arnaud Quillaud, and Dave Douglass, Lucia Fedorova, Ken Murchison, Arnaud Quillaud, and Dave
Thewlis. This specification came about via discussions at the Thewlis.
Calendaring and Scheduling Consortium.
10. References This specification came about via discussions at the Calendaring and
Scheduling Consortium.
10.1. Normative References 11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008, DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>. <http://www.rfc-editor.org/info/rfc5234>.
[RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)", Scheduling Core Object Specification (iCalendar)",
RFC 5545, DOI 10.17487/RFC5545, September 2009, RFC 5545, DOI 10.17487/RFC5545, September 2009,
<http://www.rfc-editor.org/info/rfc5545>. <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] [W3C.REC-css3-color-20110607]
A&#135;elik, T., Lilley, C., and D. Baron, "CSS Color A&#135;elik, T., Lilley, C., and D. Baron, "CSS Color
Module Level 3", World Wide Web Consortium Recommendation Module Level 3", World Wide Web Consortium Recommendation
REC-css3-color-20110607, June 2011, REC-css3-color-20110607, June 2011,
<http://www.w3.org/TR/2011/REC-css3-color-20110607>. <http://www.w3.org/TR/2011/REC-css3-color-20110607>.
10.2. Informative References 11.2. Informative References
[RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397, [RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397,
DOI 10.17487/RFC2397, August 1998, DOI 10.17487/RFC2397, August 1998,
<http://www.rfc-editor.org/info/rfc2397>. <http://www.rfc-editor.org/info/rfc2397>.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, DOI 10.17487/RFC3966, December 2004, RFC 3966, DOI 10.17487/RFC3966, December 2004,
<http://www.rfc-editor.org/info/rfc3966>. <http://www.rfc-editor.org/info/rfc3966>.
[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>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>. <http://www.rfc-editor.org/info/rfc7230>.
Appendix A. Change History (To be removed by RFC Editor before Appendix A. Change History (To be removed by RFC Editor before
publication) publication)
Changes in draft-ietf-calext-extensions-04:
1. SECDIR: Added new items to Security Considerations and added
Privacy Considerations.
2. SECDIR: fixed missing conference item in component ABNF
definitions.
3. SECDIR: editorial fixes.
Changes in draft-ietf-calext-extensions-03: Changes in draft-ietf-calext-extensions-03:
1. AD: fixed =/ ABNF syntax. 1. AD: fixed =/ ABNF syntax.
2. AD: added description for CATEGORIES. 2. AD: added description for CATEGORIES.
3. AD: Removed extra / in image ABNF. 3. AD: Removed extra / in image ABNF.
4. AD: Fixed VALUE=URI in image ABNF. 4. AD: Fixed VALUE=URI in image ABNF.
 End of changes. 30 change blocks. 
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