draft-ietf-calext-rscale-01.txt   draft-ietf-calext-rscale-02.txt 
Network Working Group C. Daboo Network Working Group C. Daboo
Internet-Draft Apple Inc. Internet-Draft Apple Inc.
Updates: 5545, 5546, 4791 (if approved) G. Yakushev Updates: 4791, 5545, 5546, 6321, 7265 G. Yakushev
Intended status: Standards Track Google Inc. (if approved) Google Inc.
Expires: May 15, 2015 November 11, 2014 Intended status: Standards Track December 10, 2014
Expires: June 13, 2015
Non-Gregorian Recurrence Rules in iCalendar Non-Gregorian Recurrence Rules in iCalendar
draft-ietf-calext-rscale-01 draft-ietf-calext-rscale-02
Abstract Abstract
This document defines how non-Gregorian recurrence rules can be This document defines how non-Gregorian recurrence rules can be
specified and used in iCalendar data, and with CalDAV servers. specified and used in iCalendar data, and with CalDAV servers.
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
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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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 May 15, 2015. This Internet-Draft will expire on June 13, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Extended RRULE Property . . . . . . . . . . . . . . . . . . . 5 4. Extended RRULE Property . . . . . . . . . . . . . . . . . . . 5
4.1. Handling Leap Months . . . . . . . . . . . . . . . . . . 6 4.1. Handling Leap Months . . . . . . . . . . . . . . . . . . 6
4.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Registering Calendar Systems . . . . . . . . . . . . . . . . 9 5. Registering Calendar Systems . . . . . . . . . . . . . . . . 9
6. Use with iTIP . . . . . . . . . . . . . . . . . . . . . . . . 10 6. Use with iTIP . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Use with CalDAV . . . . . . . . . . . . . . . . . . . . . . . 11 7. Use with xCal . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. CALDAV:supported-rscale-set Property . . . . . . . . . . 11 8. Use with jCal . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. Use with CalDAV . . . . . . . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 9.1. CALDAV:supported-rscale-set Property . . . . . . . . . . 13
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 12 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 13 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.1. Normative References . . . . . . . . . . . . . . . . . . 14
13.2. Informative References . . . . . . . . . . . . . . . . . 15
Appendix A. Change History (To be removed by RFC Editor before Appendix A. Change History (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 13 publication) . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Appendix B. xCal RELAX NG schema update . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
The iCalendar [RFC5545] data format is in widespread use to represent The iCalendar [RFC5545] data format is in widespread use to represent
calendar data. iCalendar represents dates and times using the calendar data. iCalendar represents dates and times using the
Gregorian calendar system only. It does provide a way to use non- Gregorian calendar system only. It does provide a way to use non-
Gregorian calendar systems via a "CALSCALE" property, but this has Gregorian calendar systems via a "CALSCALE" property, but this has
never been used. However, there is a need to support at least non- never been used. However, there is a need to support at least non-
Gregorian recurrence patterns to cover anniversaries, and many local, Gregorian recurrence patterns to cover anniversaries, and many local,
religious, or civil holidays based on non-Gregorian dates. religious, or civil holidays based on non-Gregorian dates.
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calendar systems to be used. With this, all the date, time and calendar systems to be used. With this, all the date, time and
period values in the iCalendar object would remain specified using period values in the iCalendar object would remain specified using
the Gregorian calendar system, but repeating patterns in other the Gregorian calendar system, but repeating patterns in other
calendar systems could be defined. It is then up to calendar user calendar systems could be defined. It is then up to calendar user
agents and servers to map between Gregorian and non-Gregorian agents and servers to map between Gregorian and non-Gregorian
calendar systems in order to expand out recurrence instances. calendar systems in order to expand out recurrence instances.
This specification does not itself define calendar systems, rather it This specification does not itself define calendar systems, rather it
utilizes the calendar system registry defined by the Unicode utilizes the calendar system registry defined by the Unicode
Consortium in their CLDR (Common Locale Data Repository) project Consortium in their CLDR (Common Locale Data Repository) project
[UNICODE.CLDR]. [UNICODE.CLDR], as implemented in the Unicode (ICU) Library
[UNICODE.ICU].
2. Conventions Used in This Document 2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
The notation used in this memo is the ABNF notation of [RFC5234] as The notation used in this memo is the ABNF notation of [RFC5234] as
used by iCalendar [RFC5545]. Any syntax elements shown below that used by iCalendar [RFC5545]. Any syntax elements shown below that
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the iTIP message SHOULD be rejected, returning a "REQUEST-STATUS" the iTIP message SHOULD be rejected, returning a "REQUEST-STATUS"
property set to the "3.1" status code (as per Section 3.6.14 of property set to the "3.1" status code (as per Section 3.6.14 of
[RFC5546]). [RFC5546]).
if the iTIP message is accepted and the calendar component treated if the iTIP message is accepted and the calendar component treated
as non-recurring, an iTIP reply with a "REQUEST-STATUS" property as non-recurring, an iTIP reply with a "REQUEST-STATUS" property
set to the "2.8" or "2.10" status codes (as per Sections 3.6.9 or set to the "2.8" or "2.10" status codes (as per Sections 3.6.9 or
3.6.11, respectively, of [RFC5546]) SHOULD be returned. 3.6.11, respectively, of [RFC5546]) SHOULD be returned.
7. Use with CalDAV 7. Use with xCal
xCal [RFC6321] defines how iCalendar data is represented in XML.
This specification extends the <recur> XML element in Section 3.6.10
of [RFC6321] in the following manner:
1. A new <rscale> XML element is defined as a child element of
<recur>. The content of this element MUST be a string whose
value is the "RSCALE" element value of the "RRULE", with case
preserved.
2. A new <skip> XML element is defined as a child element of
<recur>. The content of this element MUST be a string whose
value is the "SKIP" element value of the "RRULE", with case
preserved.
3. The "bymonth" XML element is redefined to support either numeric
or string values as its content (as per Section 4.1).
Extensions to the RELAX NG schema in Appendix A of [RFC6321] are
defined in Appendix B.
Example: the iCalendar "RRULE" property:
RRULE:RSCALE=GREGORIAN;FREQ=YEARLY;SKIP=FORWARD
would be represented in XML as:
<rrule>
<recur>
<rscale>GREGORIAN</rscale>
<freq>YEARLY</freq>
<skip>FORWARD</skip>
</recur>
</rrule>
8. Use with jCal
jCal [RFC7265] defines how iCalendar data is represented in JSON.
This specification extends the "recur" JSON object defined in
Section 3.6.10 of [RFC7265] in the following manner:
1. A new "rscale" child member is defined. This MUST be a string
whose value is the "RSCALE" element value of the "RRULE", with
case preserved.
2. A new "skip" child member is defined. This MUST be a string
whose value is the "SKIP" element value of the "RRULE", with case
preserved.
3. The "bymonth" child member is redefined to support either numeric
or string values. If the "BYMONTH" element value is an integer,
then a numeric JSON value MUST be used. If the "BYMONTH" element
value is an integer with the "L" suffix (as per Section 4.1),
then a JSON string value MUST be used.
Example: the iCalendar "RRULE" property:
RRULE:RSCALE=GREGORIAN;FREQ=YEARLY;SKIP=FORWARD
would be represented in JSON as:
[
"rrule",
{},
"recur",
{
"rscale": "GREGORIAN",
"freq": "YEARLY",
"skip": "FORWARD"
}
]
9. Use with CalDAV
The CalDAV [RFC4791] calendar access protocol allows clients and The CalDAV [RFC4791] calendar access protocol allows clients and
servers to exchange iCalendar data. In addition, CalDAV clients are servers to exchange iCalendar data. In addition, CalDAV clients are
able to query calendar data stored on the server, including time- able to query calendar data stored on the server, including time-
based queries. Since an "RSCALE" element value determines the time based queries. Since an "RSCALE" element value determines the time
ranges for recurring instances in a calendar component, CalDAV ranges for recurring instances in a calendar component, CalDAV
servers need to support it to interoperate with clients also using servers need to support it to interoperate with clients also using
the "RSCALE" element. the "RSCALE" element.
A CalDAV server advertises a CALDAV:supported-rscale-set WebDAV A CalDAV server advertises a CALDAV:supported-rscale-set WebDAV
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attempts to store iCalendar data with an "RSCALE" element value not attempts to store iCalendar data with an "RSCALE" element value not
supported by the server. supported by the server.
It is possible for an "RSCALE" value to be present in calendar data It is possible for an "RSCALE" value to be present in calendar data
on the server being accessed by a client that does not support an on the server being accessed by a client that does not support an
"RSCALE" element or its specified value. It is expected that "RSCALE" element or its specified value. It is expected that
existing clients, unaware of "RSCALE", will fail gracefully by existing clients, unaware of "RSCALE", will fail gracefully by
ignoring the calendar component, whilst still processing other ignoring the calendar component, whilst still processing other
calendar data on the server. calendar data on the server.
7.1. CALDAV:supported-rscale-set Property 9.1. CALDAV:supported-rscale-set Property
Name: supported-rscale-set Name: supported-rscale-set
Namespace: urn:ietf:params:xml:ns:caldav Namespace: urn:ietf:params:xml:ns:caldav
Purpose: Enumerates the set of supported iCalendar "RSCALE" element Purpose: Enumerates the set of supported iCalendar "RSCALE" element
values supported by the server. values supported by the server.
Protected: This property MUST be protected and SHOULD NOT be Protected: This property MUST be protected and SHOULD NOT be
returned by a PROPFIND allprop request (as defined in Section 14.2 returned by a PROPFIND allprop request (as defined in Section 14.2
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<C:supported-rscale-set <C:supported-rscale-set
xmlns:C="urn:ietf:params:xml:ns:caldav"> xmlns:C="urn:ietf:params:xml:ns:caldav">
<C:supported-rscale>GREGORIAN</C:supported-rscale> <C:supported-rscale>GREGORIAN</C:supported-rscale>
<C:supported-rscale>CHINESE</C:supported-rscale> <C:supported-rscale>CHINESE</C:supported-rscale>
<C:supported-rscale>ISLAMIC-CIVIL</C:supported-rscale> <C:supported-rscale>ISLAMIC-CIVIL</C:supported-rscale>
<C:supported-rscale>HEBREW</C:supported-rscale> <C:supported-rscale>HEBREW</C:supported-rscale>
<C:supported-rscale>ETHIOPIC</C:supported-rscale> <C:supported-rscale>ETHIOPIC</C:supported-rscale>
</C:supported-rscale-set> </C:supported-rscale-set>
8. Security Considerations 10. Security Considerations
This specification does not introduce any addition security concerns This specification does not introduce any addition security concerns
beyond those described in [RFC5545], [RFC5546], and [RFC4791]. beyond those described in [RFC5545], [RFC5546], and [RFC4791].
9. IANA Considerations 11. IANA Considerations
This document requires no IANA actions. This document requires no IANA actions.
10. Acknowledgments 12. Acknowledgments
Thanks to the following for feedback: Mark Davis, Mike Douglass, Thanks to the following for feedback: Mark Davis, Mike Douglass,
Peter Edberg, Marten Gajda, Ken Murchison, Arnaud Quillaud, Dave Peter Edberg, Marten Gajda, Philipp Kewisch, Ken Murchison, Arnaud
Thewlis, and Umaoka Yoshito. Quillaud, Dave Thewlis, and Umaoka Yoshito.
This specification originated from work at the Calendaring and This specification originated from work at the Calendaring and
Scheduling Consortium, which has helped with the development and Scheduling Consortium, which has helped with the development and
testing of implementations. testing of implementations.
11. References 13. References
11.1. Normative References 13.1. 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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault, [RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault,
"Calendaring Extensions to WebDAV (CalDAV)", RFC 4791, "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
March 2007. March 2007.
[RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed [RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, June 2007. Authoring and Versioning (WebDAV)", RFC 4918, June 2007.
skipping to change at page 13, line 23 skipping to change at page 14, line 49
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling [RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling
Core Object Specification (iCalendar)", RFC 5545, Core Object Specification (iCalendar)", RFC 5545,
September 2009. September 2009.
[RFC5546] Daboo, C., "iCalendar Transport-Independent [RFC5546] Daboo, C., "iCalendar Transport-Independent
Interoperability Protocol (iTIP)", RFC 5546, December Interoperability Protocol (iTIP)", RFC 5546, December
2009. 2009.
[RFC6321] Daboo, C., Douglass, M., and S. Lees, "xCal: The XML
Format for iCalendar", RFC 6321, August 2011.
[RFC7265] Kewisch, P., Daboo, C., and M. Douglass, "jCal: The JSON
Format for iCalendar", RFC 7265, May 2014.
[UNICODE.CLDR] [UNICODE.CLDR]
"CLDR calendar.xml Data", Unicode Consortium CLDR, "CLDR calendar.xml Data", Unicode Consortium CLDR,
<http://www.unicode.org/repos/cldr/tags/latest/common/ <http://www.unicode.org/repos/cldr/tags/latest/common/
bcp47/calendar.xml>. bcp47/calendar.xml>.
11.2. Informative References 13.2. Informative References
[ISO.8601.2004] [ISO.8601.2004]
International Organization for Standardization, "Data International Organization for Standardization, "Data
elements and interchange formats - Information interchange elements and interchange formats - Information interchange
- Representation of dates and times", ISO Standard 8601, - Representation of dates and times", ISO Standard 8601,
2004. 2004.
[UNICODE.ICU] [UNICODE.ICU]
"International Components for Unicode", Unicode Consortium "International Components for Unicode", Unicode Consortium
ICU, April 2014, <http://site.icu-project.org>. ICU, April 2014, <http://site.icu-project.org>.
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-rscale-02:
1. Added xCal and jCal changes sections and relax NG schema
appendix.
2. Added ICU reference at the end of Section 1.
Changes in draft-ietf-calext-rscale-01: Changes in draft-ietf-calext-rscale-01:
1. Editorial changes/fixes per document shepherd review. 1. Editorial changes/fixes per document shepherd review.
2. Switched CLDR reference to "tags/latest". 2. Switched CLDR reference to "tags/latest".
Changes in draft-ietf-calext-rscale-00: Changes in draft-ietf-calext-rscale-00:
1. Updated some references. 1. Updated some references.
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3. Clarified when SKIP processing occurs. 3. Clarified when SKIP processing occurs.
Changes in draft-daboo-icalendar-rscale-01: Changes in draft-daboo-icalendar-rscale-01:
1. Removed requirement that RSCALE be the first item in an RRULE. 1. Removed requirement that RSCALE be the first item in an RRULE.
2. Added BYLEAPMONTH element and removed BYMONTH "L" suffix. 2. Added BYLEAPMONTH element and removed BYMONTH "L" suffix.
3. Removed Open Issues. 3. Removed Open Issues.
Authors' Addresses Appendix B. xCal RELAX NG schema update
The following changes are made to the RELAX NG schema defined in
Appendix A of [RFC6321].
# 3.3.10 RECUR
# This extension adds type-rscale and type-skip,
# and modifies type-bymonth
value-recur = element recur {
type-rscale?,
type-freq,
(type-until | type-count)?,
element interval {
xsd:positiveInteger
}?,
type-bysecond*,
type-byminute*,
type-byhour*,
type-byday*,
type-bymonthday*,
type-byyearday*,
type-byweekno*,
type-bymonth*,
type-bysetpos*,
element wkst { type-weekday }?,
type-skip?
}
type-rscale = element rscale {
xsd:string
}
type-bymonth = element bymonth {
xsd:positiveInteger |
xsd:string
}
type-skip = element skip {
"YES" |
"BACKWARD" |
"FORWARD"
}
Authors' Addresses
Cyrus Daboo Cyrus Daboo
Apple Inc. Apple Inc.
1 Infinite Loop 1 Infinite Loop
Cupertino, CA 95014 Cupertino, CA 95014
USA USA
Email: cyrus@daboo.name Email: cyrus@daboo.name
URI: http://www.apple.com/ URI: http://www.apple.com/
Gregory Yakushev Gregory Yakushev
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