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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html><head>
<title>RFC 2445 - Internet Calendaring and Scheduling Core Object Specification (iCalendar)</title>
<meta name="description" content="RFC 2445 - Internet Calendaring and Scheduling Core Object Specification (iCalendar)">
</head>
<body bgcolor="#ffffff" text="#000000">
<h1 align="center">RFC 2445 (RFC2445)</h1>
<h3 align="center">RFC 2445 - Internet Calendaring and Scheduling Core Object Specification (iCalendar)</h3>
<hr noshade="noshade" size="2">
<pre>
Network Working Group F. Dawson
Request for Comments: 2445 Lotus
Category: Standards Track D. Stenerson
Microsoft
November 1998
Internet Calendaring and Scheduling Core Object Specification
(iCalendar)
</pre>
<h3>Status of this Memo
</h3>
<pre>
</pre> This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
<pre>
</pre>
<h3>Copyright Notice
</h3>
<pre>
</pre> Copyright (C) The Internet Society (1998). All Rights Reserved.
<pre>
</pre>
<h3>Abstract
</h3>
<pre>
</pre> There is a clear need to provide and deploy interoperable calendaring
and scheduling services for the Internet. Current group scheduling
and Personal Information Management (PIM) products are being extended
for use across the Internet, today, in proprietary ways. This memo
has been defined to provide the definition of a common format for
openly exchanging calendaring and scheduling information across the
Internet.
<pre>
</pre> This memo is formatted as a registration for a MIME media type per
[<a href="http://www.faqs.org/rfcs/rfc2048.html">RFC 2048</a>]. However, the format in this memo is equally applicable
for use outside of a MIME message content type.
<pre>
</pre> The proposed media type value is 'text/calendar'. This string would
label a media type containing calendaring and scheduling information
encoded as text characters formatted in a manner outlined below.
<pre>
</pre> This MIME media type provides a standard content type for capturing
calendar event, to-do and journal entry information. It also can be
used to convey free/busy time information. The content type is
suitable as a MIME message entity that can be transferred over MIME
based email systems, using HTTP or some other Internet transport. In
addition, the content type is useful as an object for interactions
between desktop applications using the operating system clipboard,
drag/drop or file systems capabilities.
<pre>
</pre> This memo is based on the earlier work of the vCalendar specification
for the exchange of personal calendaring and scheduling information.
In order to avoid confusion with this referenced work, this memo is
to be known as the iCalendar specification.
<pre>
</pre> This memo defines the format for specifying iCalendar object methods.
An iCalendar object method is a set of usage constraints for the
iCalendar object. For example, these methods might define scheduling
messages that request an event be scheduled, reply to an event
request, send a cancellation notice for an event, modify or replace
the definition of an event, provide a counter proposal for an
original event request, delegate an event request to another
individual, request free or busy time, reply to a free or busy time
request, or provide similar scheduling messages for a to-do or
journal entry calendar component. The iCalendar Transport-indendent
Interoperability Protocol (iTIP) defined in [ITIP] is one such
scheduling protocol.
<pre>
</pre>
<h3>Table of Contents
</h3>
<pre>
<a href="#1">1 Introduction</a>.....................................................5
<a href="#2">2 Basic Grammar and Conventions</a>....................................6
<a href="#2.1">2.1 Formatting Conventions </a>.......................................7
<a href="#2.2">2.2 Related Memos </a>................................................8
<a href="#2.3">2.3 International Considerations </a>.................................8
<a href="#3">3 Registration Information</a>.........................................8
<a href="#3.1">3.1 Content Type </a>.................................................8
<a href="#3.2">3.2 Parameters </a>...................................................9
<a href="#3.3">3.3 Content Header Fields </a>.......................................10
<a href="#3.4">3.4 Encoding Considerations </a>.....................................10
<a href="#3.5">3.5 Security Considerations </a>.....................................10
<a href="#3.6">3.6 Interoperability Considerations </a>.............................11
<a href="#3.7">3.7 Applications Which Use This Media Type </a>......................11
<a href="#3.8">3.8 Additional Information </a>......................................11
<a href="#3.9">3.9 Magic Numbers </a>...............................................11
<a href="#3.10">3.10 File Extensions </a>............................................11
<a href="#3.11">3.11 Contact for Further Information: </a>...........................12
<a href="#3.12">3.12 Intended Usage </a>.............................................12
<a href="#3.13">3.13 Authors/Change Controllers </a>.................................12
<a href="#4">4 iCalendar Object Specification</a>..................................13
<a href="#4.1">4.1 Content Lines </a>...............................................13
<a href="#4.1.1">4.1.1 List and Field Separators </a>................................16
<a href="#4.1.2">4.1.2 Multiple Values </a>..........................................16
<a href="#4.1.3">4.1.3 Binary Content </a>...........................................16
<a href="#4.1.4">4.1.4 Character Set </a>............................................17
<a href="#4.2">4.2 Property Parameters </a>.........................................17
<a href="#4.2.1">4.2.1 Alternate Text Representation </a>............................18
<a href="#4.2.2">4.2.2 Common Name </a>..............................................19
<a href="#4.2.3">4.2.3 Calendar User Type </a>.......................................20
<a href="#4.2.4">4.2.4 Delegators </a>...............................................20
<a href="#4.2.5">4.2.5 Delegatees </a>...............................................21
<a href="#4.2.6">4.2.6 Directory Entry Reference </a>................................21
<a href="#4.2.7">4.2.7 Inline Encoding </a>..........................................22
<a href="#4.2.8">4.2.8 Format Type </a>..............................................23
<a href="#4.2.9">4.2.9 Free/Busy Time Type </a>......................................23
<a href="#4.2.10">4.2.10 Language </a>................................................24
<a href="#4.2.11">4.2.11 Group or List Membership </a>................................25
<a href="#4.2.12">4.2.12 Participation Status </a>....................................25
<a href="#4.2.13">4.2.13 Recurrence Identifier Range </a>.............................27
<a href="#4.2.14">4.2.14 Alarm Trigger Relationship </a>..............................27
<a href="#4.2.15">4.2.15 Relationship Type </a>.......................................28
<a href="#4.2.16">4.2.16 Participation Role </a>......................................29
<a href="#4.2.17">4.2.17 RSVP Expectation </a>........................................29
<a href="#4.2.18">4.2.18 Sent By </a>.................................................30
<a href="#4.2.19">4.2.19 Time Zone Identifier </a>....................................30
<a href="#4.2.20">4.2.20 Value Data Types </a>........................................32
<a href="#4.3">4.3 Property Value Data Types </a>...................................32
<a href="#4.3.1">4.3.1 Binary </a>...................................................33
<a href="#4.3.2">4.3.2 Boolean </a>..................................................33
<a href="#4.3.3">4.3.3 Calendar User Address </a>....................................34
<a href="#4.3.4">4.3.4 Date </a>.....................................................34
<a href="#4.3.5">4.3.5 Date-Time </a>................................................35
<a href="#4.3.6">4.3.6 Duration </a>.................................................37
<a href="#4.3.7">4.3.7 Float </a>....................................................38
<a href="#4.3.8">4.3.8 Integer </a>..................................................38
<a href="#4.3.9">4.3.9 Period of Time </a>...........................................39
<a href="#4.3.10">4.3.10 Recurrence Rule </a>.........................................40
<a href="#4.3.11">4.3.11 Text </a>....................................................45
<a href="#4.3.12">4.3.12 Time </a>....................................................47
<a href="#4.3.13">4.3.13 URI </a>.....................................................49
<a href="#4.3.14">4.3.14 UTC Offset </a>..............................................49
<a href="#4.4">4.4 iCalendar Object </a>............................................50
<a href="#4.5">4.5 Property </a>....................................................51
<a href="#4.6">4.6 Calendar Components </a>.........................................51
<a href="#4.6.1">4.6.1 Event Component </a>..........................................52
<a href="#4.6.2">4.6.2 To-do Component </a>..........................................55
<a href="#4.6.3">4.6.3 Journal Component </a>........................................56
<a href="#4.6.4">4.6.4 Free/Busy Component </a>......................................58
<a href="#4.6.5">4.6.5 Time Zone Component </a>......................................60
<a href="#4.6.6">4.6.6 Alarm Component </a>..........................................67
<a href="#4.7">4.7 Calendar Properties </a>.........................................73
<a href="#4.7.1">4.7.1 Calendar Scale </a>...........................................73
<a href="#4.7.2">4.7.2 Method </a>...................................................74
<a href="#4.7.3">4.7.3 Product Identifier </a>.......................................75
<a href="#4.7.4">4.7.4 Version </a>..................................................76
<a href="#4.8">4.8 Component Properties </a>........................................77
<a href="#4.8.1">4.8.1 Descriptive Component Properties </a>.........................77
<a href="#4.8.1.1">4.8.1.1 Attachment </a>...........................................77
<a href="#4.8.1.2">4.8.1.2 Categories </a>...........................................78
<a href="#4.8.1.3">4.8.1.3 Classification </a>.......................................79
<a href="#4.8.1.4">4.8.1.4 Comment </a>..............................................80
<a href="#4.8.1.5">4.8.1.5 Description </a>..........................................81
<a href="#4.8.1.6">4.8.1.6 Geographic Position </a>..................................82
<a href="#4.8.1.7">4.8.1.7 Location </a>.............................................84
<a href="#4.8.1.8">4.8.1.8 Percent Complete </a>.....................................85
<a href="#4.8.1.9">4.8.1.9 Priority </a>.............................................85
<a href="#4.8.1.10">4.8.1.10 Resources </a>...........................................87
<a href="#4.8.1.11">4.8.1.11 Status </a>..............................................88
<a href="#4.8.1.12">4.8.1.12 Summary </a>.............................................89
<a href="#4.8.2">4.8.2 Date and Time Component Properties </a>.......................90
<a href="#4.8.2.1">4.8.2.1 Date/Time Completed </a>..................................90
<a href="#4.8.2.2">4.8.2.2 Date/Time End </a>........................................91
<a href="#4.8.2.3">4.8.2.3 Date/Time Due </a>........................................92
<a href="#4.8.2.4">4.8.2.4 Date/Time Start </a>......................................93
<a href="#4.8.2.5">4.8.2.5 Duration </a>.............................................94
<a href="#4.8.2.6">4.8.2.6 Free/Busy Time </a>.......................................95
<a href="#4.8.2.7">4.8.2.7 Time Transparency </a>....................................96
<a href="#4.8.3">4.8.3 Time Zone Component Properties </a>...........................97
<a href="#4.8.3.1">4.8.3.1 Time Zone Identifier </a>.................................97
<a href="#4.8.3.2">4.8.3.2 Time Zone Name </a>.......................................98
<a href="#4.8.3.3">4.8.3.3 Time Zone Offset From </a>................................99
<a href="#4.8.3.4">4.8.3.4 Time Zone Offset To </a>.................................100
<a href="#4.8.3.5">4.8.3.5 Time Zone URL </a>.......................................101
<a href="#4.8.4">4.8.4 Relationship Component Properties </a>.......................102
<a href="#4.8.4.1">4.8.4.1 Attendee </a>............................................102
<a href="#4.8.4.2">4.8.4.2 Contact </a>.............................................104
<a href="#4.8.4.3">4.8.4.3 Organizer </a>...........................................106
<a href="#4.8.4.4">4.8.4.4 Recurrence ID </a>.......................................107
<a href="#4.8.4.5">4.8.4.5 Related To </a>..........................................109
<a href="#4.8.4.6">4.8.4.6 Uniform Resource Locator </a>............................110
<a href="#4.8.4.7">4.8.4.7 Unique Identifier </a>...................................111
<a href="#4.8.5">4.8.5 Recurrence Component Properties </a>.........................112
<a href="#4.8.5.1">4.8.5.1 Exception Date/Times </a>................................112
<a href="#4.8.5.2">4.8.5.2 Exception Rule </a>......................................114
<a href="#4.8.5.3">4.8.5.3 Recurrence Date/Times </a>...............................115
<a href="#4.8.5.4">4.8.5.4 Recurrence Rule </a>.....................................117
<a href="#4.8.6">4.8.6 Alarm Component Properties </a>..............................126
<a href="#4.8.6.1">4.8.6.1 Action </a>..............................................126
<a href="#4.8.6.2">4.8.6.2 Repeat Count </a>........................................126
<a href="#4.8.6.3">4.8.6.3 Trigger </a>.............................................127
<a href="#4.8.7">4.8.7 Change Management Component Properties </a>..................129
<a href="#4.8.7.1">4.8.7.1 Date/Time Created </a>...................................129
<a href="#4.8.7.2">4.8.7.2 Date/Time Stamp </a>.....................................130
<a href="#4.8.7.3">4.8.7.3 Last Modified </a>.......................................131
<a href="#4.8.7.4">4.8.7.4 Sequence Number </a>.....................................131
<a href="#4.8.8">4.8.8 Miscellaneous Component Properties </a>......................133
<a href="#4.8.8.1">4.8.8.1 Non-standard Properties </a>.............................133
<a href="#4.8.8.2">4.8.8.2 Request Status </a>......................................134
<a href="#5">5 iCalendar Object Examples</a>......................................136
<a href="#6">6 Recommended Practices</a>..........................................140
<a href="#7">7 Registration of Content Type Elements</a>..........................141
<a href="#7.1">7.1 Registration of New and Modified iCalendar Object Methods </a>..141
<a href="#7.2">7.2 Registration of New Properties </a>.............................141
<a href="#7.2.1">7.2.1 Define the property </a>.....................................142
<a href="#7.2.2">7.2.2 Post the Property definition </a>............................143
<a href="#7.2.3">7.2.3 Allow a comment period </a>..................................143
<a href="#7.2.4">7.2.4 Submit the property for approval </a>........................143
<a href="#7.3">7.3 Property Change Control </a>....................................143
<a href="#8">8 References</a>.....................................................144
<a href="#9">9 Acknowledgments</a>................................................145
<a href="#10">10 Authors' and Chairs' Addresses</a>................................146
<a href="#11">11 Full Copyright Statement</a>......................................148
</pre>
<h3><a name="1">1</a> Introduction</h3>
</p>
<p> The use of calendaring and scheduling has grown considerably in the
last decade. Enterprise and inter-enterprise business has become
dependent on rapid scheduling of events and actions using this
information technology. However, the longer term growth of
calendaring and scheduling, is currently limited by the lack of
Internet standards for the message content types that are central to
these knowledgeware applications. This memo is intended to progress
the level of interoperability possible between dissimilar calendaring
and scheduling applications. This memo defines a MIME content type
for exchanging electronic calendaring and scheduling information. The
Internet Calendaring and Scheduling Core Object Specification, or
iCalendar, allows for the capture and exchange of information
normally stored within a calendaring and scheduling application; such
as a Personal Information Manager (PIM) or a Group Scheduling
product.
<pre>
</pre> The iCalendar format is suitable as an exchange format between
applications or systems. The format is defined in terms of a MIME
content type. This will enable the object to be exchanged using
several transports, including but not limited to SMTP, HTTP, a file
system, desktop interactive protocols such as the use of a memory-
based clipboard or drag/drop interactions, point-to-point
asynchronous communication, wired-network transport, or some form of
<pre>
</pre> unwired transport such as infrared might also be used.
<pre>
</pre> The memo also provides for the definition of iCalendar object methods
that will map this content type to a set of messages for supporting
calendaring and scheduling operations such as requesting, replying
to, modifying, and canceling meetings or appointments, to-dos and
journal entries. The iCalendar object methods can be used to define
other calendaring and scheduling operations such a requesting for and
replying with free/busy time data. Such a scheduling protocol is
defined in the iCalendar Transport-independent Interoperability
Protocol (iTIP) defined in [ITIP].
<pre>
</pre> The memo also includes a formal grammar for the content type based on
the Internet ABNF defined in [<a href="http://www.faqs.org/rfcs/rfc2234.html">RFC 2234</a>]. This ABNF is required for
the implementation of parsers and to serve as the definitive
reference when ambiguities or questions arise in interpreting the
descriptive prose definition of the memo.
<pre>
</pre>
<h3><a name="2">2</a> Basic Grammar and Conventions</h3>
</p>
<p> 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 interoperated as described in
[<a href="http://www.faqs.org/rfcs/rfc2119.html">RFC 2119</a>].
<pre>
</pre> This memo makes use of both a descriptive prose and a more formal
notation for defining the calendaring and scheduling format.
<pre>
</pre> The notation used in this memo is the ABNF notation of [<a href="http://www.faqs.org/rfcs/rfc2234.html">RFC 2234</a>].
Readers intending on implementing this format defined in this memo
should be familiar with this notation in order to properly interpret
the specifications of this memo.
<pre>
</pre> All numeric and hexadecimal values used in this memo are given in
decimal notation.
<pre>
</pre> All names of properties, property parameters, enumerated property
values and property parameter values are case-insensitive. However,
all other property values are case-sensitive, unless otherwise
stated.
<pre>
Note: All indented editorial notes, such as this one, are
intended to provide the reader with additional information. The
information is not essential to the building of an
implementation conformant with this memo. The information is
provided to highlight a particular feature or characteristic of
the memo.
</pre> The format for the iCalendar object is based on the syntax of the
[<a href="http://www.faqs.org/rfcs/rfc2425.html">RFC 2425</a>] content type. While the iCalendar object is not a profile
of the [<a href="http://www.faqs.org/rfcs/rfc2425.html">RFC 2425</a>] content type, it does reuse a number of the
elements from the [<a href="http://www.faqs.org/rfcs/rfc2425.html">RFC 2425</a>] specification.
<pre>
</pre>
<h3><a name="2.1">2.1</a> Formatting Conventions</h3>
</p>
<p> The mechanisms defined in this memo are defined in prose. Many of the
terms used to describe these have common usage that is different than
the standards usage of this memo. In order to reference within this
memo elements of the calendaring and scheduling model, core object
(this memo) or interoperability protocol [ITIP] some formatting
conventions have been used. Calendaring and scheduling roles are
referred to in quoted-strings of text with the first character of
each word in upper case. For example, "Organizer" refers to a role of
a "Calendar User" within the scheduling protocol defined by [ITIP].
Calendar components defined by this memo are referred to with
capitalized, quoted-strings of text. All calendar components start
with the letter "V". For example, "VEVENT" refers to the event
calendar component, "VTODO" refers to the to-do calendar component
and "VJOURNAL" refers to the daily journal calendar component.
Scheduling methods defined by [ITIP] are referred to with
capitalized, quoted-strings of text. For example, "REQUEST" refers to
the method for requesting a scheduling calendar component be created
or modified, "REPLY" refers to the method a recipient of a request
uses to update their status with the "Organizer" of the calendar
component.
<pre>
</pre> The properties defined by this memo are referred to with capitalized,
quoted-strings of text, followed by the word "property". For example,
"ATTENDEE" property refers to the iCalendar property used to convey
the calendar address of a calendar user. Property parameters defined
by this memo are referred to with lowercase, quoted-strings of text,
followed by the word "parameter". For example, "value" parameter
refers to the iCalendar property parameter used to override the
default data type for a property value. Enumerated values defined by
this memo are referred to with capitalized text, either alone or
followed by the word "value". For example, the "MINUTELY" value can
be used with the "FREQ" component of the "RECUR" data type to specify
repeating components based on an interval of one minute or more.
<pre>
</pre>
<h3><a name="2.2">2.2</a> Related Memos</h3>
</p>
<p> Implementers will need to be familiar with several other memos that,
along with this memo, form a framework for Internet calendaring and
scheduling standards. This memo, [ICAL], specifies a core
specification of objects, data types, properties and property
parameters.
<pre>
</pre> [ITIP] - specifies an interoperability protocol for scheduling
between different implementations;
<pre>
</pre> [IMIP] specifies an Internet email binding for [ITIP].
<pre>
</pre> This memo does not attempt to repeat the specification of concepts or
definitions from these other memos. Where possible, references are
made to the memo that provides for the specification of these
concepts or definitions.
<pre>
</pre>
<h3><a name="2.3">2.3</a> International Considerations</h3>
</p>
<p> In the rest of this document, descriptions of characters are of the
form "character name (codepoint)", where "codepoint" is from the US-
ASCII character set. The "character name" is the authoritative
description; (codepoint) is a reference to that character in US-ASCII
or US-ASCII compatible sets (for example the ISO-8859-x family, UTF-
8, ISO-2022-xx, KOI8-R). If a non-US-ASCII compatible character set
is used, appropriate code-point from that character set MUST be
chosen instead. Use of non-US-ASCII-compatible character sets is NOT
recommended.
<pre>
</pre>
<h3><a name="3">3</a> Registration Information</h3>
</p>
<p> The Calendaring and Scheduling Core Object Specification is intended
for use as a MIME content type. However, the implementation of the
memo is in no way limited solely as a MIME content type.
<pre>
</pre>
<h3><a name="3.1">3.1</a> Content Type</h3>
</p>
<p> The following text is intended to register this memo as the MIME
content type "text/calendar".
<pre>
To: <a href="mailto:ietf-types@uninett.no">ietf-types@uninett.no</a>
Subject: Registration of MIME content type text/calendar.
MIME media type name: text
MIME subtype name: calendar
</pre>
<h3><a name="3.2">3.2</a> Parameters</h3>
</p>
<p> Required parameters: none
<pre>
</pre> Optional parameters: charset, method, component and optinfo
<pre>
</pre> The "charset" parameter is defined in [<a href="http://www.faqs.org/rfcs/rfc2046.html">RFC 2046</a>] for other body
parts. It is used to identify the default character set used within
the body part.
<pre>
</pre> The "method" parameter is used to convey the iCalendar object method
or transaction semantics for the calendaring and scheduling
information. It also is an identifier for the restricted set of
properties and values that the iCalendar object consists of. The
parameter is to be used as a guide for applications interpreting the
information contained within the body part. It SHOULD NOT be used to
exclude or require particular pieces of information unless the
identified method definition specifically calls for this behavior.
Unless specifically forbidden by a particular method definition, a
text/calendar content type can contain any set of properties
permitted by the Calendaring and Scheduling Core Object
Specification. The "method" parameter MUST be the same value as that
specified in the "METHOD" component property in the iCalendar object.
If one is present, the other MUST also be present.
<pre>
</pre> The value for the "method" parameter is defined as follows:
<pre>
method = 1*(ALPHA / DIGIT / "-")
; IANA registered iCalendar object method
</pre> The "component" parameter conveys the type of iCalendar calendar
component within the body part. If the iCalendar object contains more
than one calendar component type, then multiple component parameters
MUST be specified.
<pre>
</pre> The value for the "component" parameter is defined as follows:
<pre>
component = ("VEVENT" / "VTODO" / "VJOURNAL" / "VFREEBUSY"
/ "VTIMEZONE" / x-name / iana-token)
</pre> The "optinfo" parameter conveys optional information about the
iCalendar object within the body part. This parameter can only
specify semantics already specified by the iCalendar object and that
can be otherwise determined by parsing the body part. In addition,
the optional information specified by this parameter MUST be
consistent with that information specified by the iCalendar object.
For example, it can be used to convey the "Attendee" response status
to a meeting request. The parameter value consists of a string value.
<pre>
</pre> The parameter can be specified multiple times.
<pre>
</pre> This parameter MAY only specify semantics already specified by the
iCalendar object and that can be otherwise determined by parsing the
body part.
<pre>
</pre> The value for the "optinfo" parameter is defined as follows:
<pre>
optinfo = infovalue / qinfovalue
infovalue = iana-token / x-name
qinfovalue = DQUOTE (infovalue) DQUOTE
</pre>
<h3><a name="3.3">3.3</a> Content Header Fields</h3>
</p>
<p> Optional content header fields: Any header fields defined by [RFC
2045].
<pre>
</pre>
<h3><a name="3.4">3.4</a> Encoding Considerations</h3>
</p>
<p> This MIME content type can contain 8bit characters, so the use of
quoted-printable or BASE64 MIME content-transfer-encodings might be
necessary when iCalendar objects are transferred across protocols
restricted to the 7bit repertoire. Note that a text valued property
in the content entity can also have content encoding of special
characters using a BACKSLASH character (US-ASCII decimal 92)
escapement technique. This means that content values can end up
encoded twice.
<pre>
</pre>
<h3><a name="3.5">3.5</a> Security Considerations</h3>
</p>
<p> SPOOFING - - In this memo, the "Organizer" is the only person
authorized to make changes to an existing "VEVENT", "VTODO",
"VJOURNAL" calendar component and redistribute the updates to the
"Attendees". An iCalendar object that maliciously changes or cancels
an existing "VEVENT", "VTODO" or "VJOURNAL" or "VFREEBUSY" calendar
component might be constructed by someone other than the "Organizer"
and sent to the "Attendees". In addition in this memo, other than the
"Organizer", an "Attendee" of a "VEVENT", "VTODO", "VJOURNAL"
calendar component is the only other person authorized to update any
parameter associated with their "ATTENDEE" property and send it to
the "Organizer". An iCalendar object that maliciously changes the
"ATTENDEE" parameters can be constructed by someone other than the
real "Attendee" and sent to the "Organizer".
<pre>
</pre> PROCEDURAL ALARMS - - An iCalendar object can be created that
contains a "VEVENT" and "VTODO" calendar component with "VALARM"
calendar components. The "VALARM" calendar component can be of type
PROCEDURE and can have an attachment containing some sort of
executable program. Implementations that incorporate these types of
alarms are subject to any virus or malicious attack that might occur
as a result of executing the attachment.
<pre>
</pre> ATTACHMENTS - - An iCalendar object can include references to Uniform
Resource Locators that can be programmed resources.
<pre>
</pre> Implementers and users of this memo should be aware of the network
security implications of accepting and parsing such information. In
addition, the security considerations observed by implementations of
electronic mail systems should be followed for this memo.
<pre>
</pre>
<h3><a name="3.6">3.6</a> Interoperability Considerations</h3>
</p>
<p> This MIME content type is intended to define a common format for
conveying calendaring and scheduling information between different
systems. It is heavily based on the earlier [VCAL] industry
specification.
<pre>
</pre>
<h3><a name="3.7">3.7</a> Applications Which Use This Media Type</h3>
</p>
<p> This content-type is designed for widespread use by Internet
calendaring and scheduling applications. In addition, applications in
the workflow and document management area might find this content-
type applicable. The [ITIP] and [IMIP] Internet protocols directly
use this content-type also. Future work on an Internet calendar
access protocol will utilize this content-type too.
<pre>
</pre>
<h3><a name="3.8">3.8</a> Additional Information</h3>
</p>
<p> This memo defines this content-type.
<pre>
</pre>
<h3><a name="3.9">3.9</a> Magic Numbers</h3>
</p>
<p> None.
<pre>
</pre>
<h3><a name="3.10">3.10</a> File Extensions</h3>
</p>
<p> The file extension of "ics" is to be used to designate a file
containing (an arbitrary set of) calendaring and scheduling
information consistent with this MIME content type.
<pre>
</pre> The file extension of "ifb" is to be used to designate a file
containing free or busy time information consistent with this MIME
content type.
<pre>
</pre> Macintosh file type codes: The file type code of "iCal" is to be used
in Apple MacIntosh operating system environments to designate a file
containing calendaring and scheduling information consistent with
this MIME media type.
<pre>
</pre> The file type code of "iFBf" is to be used in Apple MacIntosh
operating system environments to designate a file containing free or
busy time information consistent with this MIME media type.
<pre>
</pre>
<h3><a name="3.11">3.11</a> Contact for Further Information:</h3>
</p>
<p> Frank Dawson
6544 Battleford Drive
Raleigh, NC 27613-3502
919-676-9515 (Telephone)
919-676-9564 (Data/Facsimile)
<a href="mailto:Frank_Dawson@Lotus.com">Frank_Dawson@Lotus.com</a> (Internet Mail)
<pre>
Derik Stenerson
One Microsoft Way
Redmond, WA 98052-6399
425-936-5522 (Telephone)
425-936-7329 (Facsimile)
<a href="mailto:deriks@microsoft.com">deriks@microsoft.com</a> (Internet Mail)
</pre>
<h3><a name="3.12">3.12</a> Intended Usage</h3>
</p>
<p> COMMON
<pre>
</pre>
<h3><a name="3.13">3.13</a> Authors/Change Controllers</h3>
</p>
<p> Frank Dawson
6544 Battleford Drive
Raleigh, NC 27613-3502
919-676-9515 (Telephone)
919-676-9564 (Data/Facsimile)
<a href="mailto:Frank_Dawson@Lotus.com">Frank_Dawson@Lotus.com</a> (Internet Mail)
<pre>
Derik Stenerson
One Microsoft Way
Redmond, WA 98052-6399
425-936-5522 (Telephone)
425-936-7329 (Facsimile)
<a href="mailto:deriks@microsoft.com">deriks@microsoft.com</a> (Internet Mail)
</pre>
<h3><a name="4">4</a> iCalendar Object Specification</h3>
</p>
<p> The following sections define the details of a Calendaring and
Scheduling Core Object Specification. This information is intended to
be an integral part of the MIME content type registration. In
addition, this information can be used independent of such content
registration. In particular, this memo has direct applicability for
use as a calendaring and scheduling exchange format in file-, memory-
or network-based transport mechanisms.
<pre>
</pre>
<h3><a name="4.1">4.1</a> Content Lines</h3>
</p>
<p> The iCalendar object is organized into individual lines of text,
called content lines. Content lines are delimited by a line break,
which is a CRLF sequence (US-ASCII decimal 13, followed by US-ASCII
decimal 10).
<pre>
</pre> Lines of text SHOULD NOT be longer than 75 octets, excluding the line
break. Long content lines SHOULD be split into a multiple line
representations using a line "folding" technique. That is, a long
line can be split between any two characters by inserting a CRLF
immediately followed by a single linear white space character (i.e.,
SPACE, US-ASCII decimal 32 or HTAB, US-ASCII decimal 9). Any sequence
of CRLF followed immediately by a single linear white space character
is ignored (i.e., removed) when processing the content type.
<pre>
</pre> For example the line:
<pre>
DESCRIPTION:This is a long description that exists on a long line.
</pre> Can be represented as:
<pre>
DESCRIPTION:This is a lo
ng description
that exists on a long line.
</pre> The process of moving from this folded multiple line representation
to its single line representation is called "unfolding". Unfolding is
accomplished by removing the CRLF character and the linear white
space character that immediately follows.
<pre>
</pre> When parsing a content line, folded lines MUST first be unfolded
according to the unfolding procedure described above. When generating
a content line, lines longer than 75 octets SHOULD be folded
according to the folding procedure described above.
<pre>
</pre> The content information associated with an iCalendar object is
formatted using a syntax similar to that defined by [<a href="http://www.faqs.org/rfcs/rfc2425.html">RFC 2425</a>]. That
is, the content information consists of CRLF-separated content lines.
<pre>
</pre> The following notation defines the lines of content in an iCalendar
object:
<pre>
contentline = name *(";" param ) ":" value CRLF
; This ABNF is just a general definition for an initial parsing
; of the content line into its property name, parameter list,
; and value string
; When parsing a content line, folded lines MUST first
; be unfolded according to the unfolding procedure
; described above. When generating a content line, lines
; longer than 75 octets SHOULD be folded according to
; the folding procedure described above.
name = x-name / iana-token
iana-token = 1*(ALPHA / DIGIT / "-")
; iCalendar identifier registered with IANA
x-name = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
; Reservered for experimental use. Not intended for use in
; released products.
vendorid = 3*(ALPHA / DIGIT) ;Vendor identification
param = param-name "=" param-value
*("," param-value)
; Each property defines the specific ABNF for the parameters
; allowed on the property. Refer to specific properties for
; precise parameter ABNF.
param-name = iana-token / x-token
param-value = paramtext / quoted-string
paramtext = *SAFE-CHAR
value = *VALUE-CHAR
quoted-string = DQUOTE *QSAFE-CHAR DQUOTE
NON-US-ASCII = %x80-F8
; Use restricted by charset parameter
; on outer MIME object (UTF-8 preferred)
QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-US-ASCII
; Any character except CTLs and DQUOTE
SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E
/ NON-US-ASCII
; Any character except CTLs, DQUOTE, ";", ":", ","
VALUE-CHAR = WSP / %x21-7E / NON-US-ASCII
; Any textual character
CR = %x0D
; carriage return
LF = %x0A
; line feed
CRLF = CR LF
; Internet standard newline
CTL = %x00-08 / %x0A-1F / %x7F
; Controls
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39
; 0-9
DQUOTE = %x22
; Quotation Mark
WSP = SPACE / HTAB
SPACE = %x20
HTAB = %x09
</pre> The property value component of a content line has a format that is
property specific. Refer to the section describing each property for
a definition of this format.
<pre>
</pre> All names of properties, property parameters, enumerated property
values and property parameter values are case-insensitive. However,
all other property values are case-sensitive, unless otherwise
stated.
<pre>
</pre>
<h3><a name="4.1.1">4.1.1</a> List and Field Separators</h3>
</p>
<p> Some properties and parameters allow a list of values. Values in a
list of values MUST be separated by a COMMA character (US-ASCII
decimal 44). There is no significance to the order of values in a
list. For those parameter values (such as those that specify URI
values) that are specified in quoted-strings, the individual quoted-
strings are separated by a COMMA character (US-ASCII decimal 44).
<pre>
</pre> Some property values are defined in terms of multiple parts. These
structured property values MUST have their value parts separated by a
SEMICOLON character (US-ASCII decimal 59).
<pre>
</pre> Some properties allow a list of parameters. Each property parameter
in a list of property parameters MUST be separated by a SEMICOLON
character (US-ASCII decimal 59).
<pre>
</pre> Property parameters with values containing a COLON, a SEMICOLON or a
COMMA character MUST be placed in quoted text.
<pre>
</pre> For example, in the following properties a SEMICOLON is used to
separate property parameters from each other, and a COMMA is used to
separate property values in a value list.
<pre>
ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:MAILTO:
<a href="mailto:jsmith@host.com">jsmith@host.com</a>
RDATE;VALUE=DATE:19970304,19970504,19970704,19970904
</pre>
<h3><a name="4.1.2">4.1.2</a> Multiple Values</h3>
</p>
<p> Some properties defined in the iCalendar object can have multiple
values. The general rule for encoding multi-valued items is to simply
create a new content line for each value, including the property
name. However, it should be noted that some properties support
encoding multiple values in a single property by separating the
values with a COMMA character (US-ASCII decimal 44). Individual
property definitions should be consulted for determining whether a
specific property allows multiple values and in which of these two
forms.
<pre>
</pre>
<h3><a name="4.1.3">4.1.3</a> Binary Content</h3>
</p>
<p> Binary content information in an iCalendar object SHOULD be
referenced using a URI within a property value. That is the binary
content information SHOULD be placed in an external MIME entity that
can be referenced by a URI from within the iCalendar object. In
applications where this is not feasible, binary content information
<pre>
</pre> can be included within an iCalendar object, but only after first
encoding it into text using the "BASE64" encoding method defined in
[<a href="http://www.faqs.org/rfcs/rfc2045.html">RFC 2045</a>]. Inline binary contact SHOULD only be used in applications
whose special circumstances demand that an iCalendar object be
expressed as a single entity. A property containing inline binary
content information MUST specify the "ENCODING" property parameter.
Binary content information placed external to the iCalendar object
MUST be referenced by a uniform resource identifier (URI).
<pre>
</pre> The following example specifies an "ATTACH" property that references
an attachment external to the iCalendar object with a URI reference:
<pre>
ATTACH:<a href="http://xyz.com/public/quarterly-report.doc">http://xyz.com/public/quarterly-report.doc</a>
</pre> The following example specifies an "ATTACH" property with inline
binary encoded content information:
<pre>
ATTACH;FMTTYPE=image/basic;ENCODING=BASE64;VALUE=BINARY:
MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1U
EBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIE
<...remainder of "BASE64" encoded binary data...>
</pre>
<h3><a name="4.1.4">4.1.4</a> Character Set</h3>
</p>
<p> There is not a property parameter to declare the character set used
in a property value. The default character set for an iCalendar
object is UTF-8 as defined in [<a href="http://www.faqs.org/rfcs/rfc2279.html">RFC 2279</a>].
<pre>
</pre> The "charset" Content-Type parameter can be used in MIME transports
to specify any other IANA registered character set.
<pre>
</pre>
<h3><a name="4.2">4.2</a> Property Parameters</h3>
</p>
<p> A property can have attributes associated with it. These "property
parameters" contain meta-information about the property or the
property value. Property parameters are provided to specify such
information as the location of an alternate text representation for a
property value, the language of a text property value, the data type
of the property value and other attributes.
<pre>
</pre> Property parameter values that contain the COLON (US-ASCII decimal
58), SEMICOLON (US-ASCII decimal 59) or COMMA (US-ASCII decimal 44)
character separators MUST be specified as quoted-string text values.
Property parameter values MUST NOT contain the DOUBLE-QUOTE (US-ASCII
decimal 22) character. The DOUBLE-QUOTE (US-ASCII decimal 22)
character is used as a delimiter for parameter values that contain
restricted characters or URI text. For example:
<pre>
DESCRIPTION;ALTREP="http://www.wiz.org":The Fall'98 Wild Wizards
Conference - - Las Vegas, NV, USA
</pre> Property parameter values that are not in quoted strings are case
insensitive.
<pre>
</pre> The general property parameters defined by this memo are defined by
the following notation:
<pre>
parameter = altrepparam ; Alternate text representation
/ cnparam ; Common name
/ cutypeparam ; Calendar user type
/ delfromparam ; Delegator
/ deltoparam ; Delegatee
/ dirparam ; Directory entry
/ encodingparam ; Inline encoding
/ fmttypeparam ; Format type
/ fbtypeparam ; Free/busy time type
/ languageparam ; Language for text
/ memberparam ; Group or list membership
/ partstatparam ; Participation status
/ rangeparam ; Recurrence identifier range
/ trigrelparam ; Alarm trigger relationship
/ reltypeparam ; Relationship type
/ roleparam ; Participation role
/ rsvpparam ; RSVP expectation
/ sentbyparam ; Sent by
/ tzidparam ; Reference to time zone object
/ valuetypeparam ; Property value data type
/ ianaparam
; Some other IANA registered iCalendar parameter.
/ xparam
; A non-standard, experimental parameter.
ianaparam = iana-token "=" param-value *("," param-value)
xparam =x-name "=" param-value *("," param-value)
</pre>
<h3><a name="4.2.1">4.2.1</a> Alternate Text Representation</h3>
</p>
<p> Parameter Name: ALTREP
<pre>
</pre> Purpose: To specify an alternate text representation for the property
value.
<pre>
</pre> Format Definition: The property parameter is defined by the following
notation:
<pre>
altrepparam = "ALTREP" "=" DQUOTE uri DQUOTE
</pre> Description: The parameter specifies a URI that points to an
alternate representation for a textual property value. A property
specifying this parameter MUST also include a value that reflects the
default representation of the text value. The individual URI
parameter values MUST each be specified in a quoted-string.
<pre>
</pre> Example:
<pre>
DESCRIPTION;ALTREP="CID:<<a href="mailto:part3.msg.970415T083000@host.com">part3.msg.970415T083000@host.com</a>>":Project
XYZ Review Meeting will include the following agenda items: (a)
Market Overview, (b) Finances, (c) Project Management
</pre> The "ALTREP" property parameter value might point to a "text/html"
content portion.
<pre>
Content-Type:text/html
Content-Id:<<a href="mailto:part3.msg.970415T083000@host.com">part3.msg.970415T083000@host.com</a>>
<html><body>
<p><b>Project XYZ Review Meeting</b> will include the following
agenda items:<ol><li>Market
Overview</li><li>Finances</li><li>Project Management</li></ol></p>
</body></html>
</pre>
<h3><a name="4.2.2">4.2.2</a> Common Name</h3>
</p>
<p> Parameter Name: CN
<pre>
</pre> Purpose: To specify the common name to be associated with the
calendar user specified by the property.
<pre>
</pre> Format Definition: The property parameter is defined by the following
notation:
<pre>
cnparam = "CN" "=" param-value
</pre> Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the common name to be
associated with the calendar user specified by the property. The
parameter value is text. The parameter value can be used for display
text to be associated with the calendar address specified by the
property.
<pre>
</pre> Example:
<pre>
ORGANIZER;CN="John Smith":<a href="mailto:MAILTO:jsmith@host.com">MAILTO:jsmith@host.com</a>
</pre>
<h3><a name="4.2.3">4.2.3</a> Calendar User Type</h3>
</p>
<p> Parameter Name: CUTYPE
<pre>
</pre> Purpose: To specify the type of calendar user specified by the
property.
<pre>
</pre> Format Definition: The property parameter is defined by the following
notation:
<pre>
cutypeparam = "CUTYPE" "="
("INDIVIDUAL" ; An individual
/ "GROUP" ; A group of individuals
/ "RESOURCE" ; A physical resource
/ "ROOM" ; A room resource
/ "UNKNOWN" ; Otherwise not known
/ x-name ; Experimental type
/ iana-token) ; Other IANA registered
; type
; Default is INDIVIDUAL
</pre> Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the type of calendar
user specified by the property. If not specified on a property that
allows this parameter, the default is INDIVIDUAL.
<pre>
</pre> Example:
<pre>
ATTENDEE;CUTYPE=GROUP:<a href="mailto:MAILTO:ietf-calsch@imc.org">MAILTO:ietf-calsch@imc.org</a>
</pre>
<h3><a name="4.2.4">4.2.4</a> Delegators</h3>
</p>
<p> Parameter Name: DELEGATED-FROM
<pre>
</pre> Purpose: To specify the calendar users that have delegated their
participation to the calendar user specified by the property.
<pre>
</pre> Format Definition: The property parameter is defined by the following
notation:
<pre>
delfromparam = "DELEGATED-FROM" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
</pre> Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. This parameter can be specified on a property
that has a value type of calendar address. This parameter specifies
those calendar uses that have delegated their participation in a
group scheduled event or to-do to the calendar user specified by the
property. The value MUST be a MAILTO URI as defined in [<a href="http://www.faqs.org/rfcs/rfc1738.html">RFC 1738</a>].
The individual calendar address parameter values MUST each be