Network Working Group                                           C. Daboo
Internet-Draft                                                     Apple
Updates: 5545,6350 (if approved)                         August 29, 2012
Intended status: Standards Track
Expires: March 2, 2013


            Parameter Value Encoding in iCalendar and vCard
              draft-daboo-ical-vcard-parameter-encoding-01

Abstract

   This specification updates the iCalendar and vCard data formats to
   allow parameter values to include certain characters forbidden by the
   existing specifications.

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 March 2, 2013.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 3
   3.  Parameter Value Encoding Scheme . . . . . . . . . . . . . . . . 3
     3.1.  iCalendar Example . . . . . . . . . . . . . . . . . . . . . 4
     3.2.  vCard Examples  . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Change History (To be removed by RFC Editor
                before publication)  . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 5






































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.  Introduction

   The iCalendar [RFC5545] specification defines a standard way to
   describe calendar data.  The vCard [RFC6350] specification defines a
   standard way to describe contact data.  Both of these use a similar
   text-based data format.  Each iCalendar and vCard data object can
   include "properties" which have "parameters" and a "value".  The
   value of a "parameter" is typically a token or URI value, but a
   "generic" text value is also allowed.  However, the syntax rules for
   both iCalendar and vCard prevent the use of a double-quote character
   or control characters in such values, though double-quote and some
   subset of control characters are allowed in the actual property
   values.

   As more and more extensions are being developed for these data
   formats, there is a need to allow at least double-quotes, line feeds
   and tabs to be included in parameter values.  The \-escaping
   mechanism used for property text values is not defined for use with
   parameter values and cannot be easily used in a backwards compatible
   manner.  This specification defines a new character escaping
   mechanism, compatible with existing parsers and chosen to minimise
   any impact on existing data.


.  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].


.  Parameter Value Encoding Scheme

   This specification defines the ^ character (U+005E - Circumflex
   Accent) as an escape character in parameter values whose value type
   is defined using the "param-value" syntax element (Section 3.1 of
   iCalendar [RFC5545] and Section 3.3 of vCard [RFC6350]).  The
   ^-escaping mechanism can be used when the value is either unquoted or
   quoted (i.e., whether or not the value is surrounded by double-
   quotes).  When used, the combination of ^ plus one other character is
   interpreted as a single character as per the table below:









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          +---------------------+-------------------------------+
          | Escape Sequence     | Character                     |
          +---------------------+-------------------------------+
          | ^' (U+005E, U+0027) | U+0022 (Quotation Mark)       |
          | ^n (U+005E, U+006E) | U+000A (Line Feed)            |
          | ^t (U+005E, U+0074) | U+0009 (Character Tabulation) |
          | ^^ (U+005E, U+005E) | U+005E (Circumflex Accent)    |
          +---------------------+-------------------------------+

   When generating iCalendar or vCard parameter values, the characters
   in the second column above MUST be escaped using the sequence from
   the first column.  When parsing iCalendar or vCard parameter values,
   the two character sequence from the first column MUST be replaced by
   the single character from the second column.  If a ^ (U+005E)
   character is followed by any other character than the ones above,
   parsers SHOULD leave the ^ character in place.

   In addition to the escaping procedure outlined above, text parameter
   values MUST also have line break character sequences canonicalized
   into a single line feed (U+000A) character when the parameter value
   is generated.  Specifically, any single carriage return character
   (U+000D) or the two character combination of carriage return followed
   by line feed (U+000D, U+000A) MUST be mapped to ^n in the generated
   parameter value.  When parsing a parameter value with ^n, clients can
   replace that with the appropriate line break character sequence for
   the system they are running on.

3.1.  iCalendar Example

   An "ATTENDEE" property with a "CN" parameter whose value includes two
   double-quote characters.  The parameter value is not quoted as there
   are no characters in the value that would trigger quoting as required
   by iCalendar.

   ATTENDEE;CN=George Herman ^'Babe^' Ruth:mailto:babe@example.com

   The unescaped parameter value is

   George Herman "Babe" Ruth

3.2.  vCard Examples

   A "GEO" property with a "X-ADDRESS" parameter whose value includes
   several line feed characters.  The parameter value is also quoted
   since it contains a comma which triggers quoting as required by
   vCard.

   GEO;X-ADDRESS="Pittsburgh Pirates^n115 Federal St^nPitt



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    sburgh, PA 15212":geo:40.446816,-80.00566

   The unescaped parameter value is (where each line is terminated by a
   line break character sequence)

   Pittsburgh Pirates
   115 Federal St
   Pittsburgh, PA 15212


.  Security Considerations

   There are no additional security issues beyond those of iCalendar
   [RFC5545] and vCard [RFC6350].


.  IANA Considerations

   There are none.


.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5545]  Desruisseaux, B., "Internet Calendaring and Scheduling
              Core Object Specification (iCalendar)", RFC 5545,
              September 2009.

   [RFC6350]  Perreault, S., "vCard Format Specification", RFC 6350,
              August 2011.


Appendix A.  Change History (To be removed by RFC Editor before
             publication)

   Changes in -01:

   1.  Tweaked vCard example line-folding.











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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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