RFC 2445
Internet Calendaring and Scheduling Core Object Specification (iCalendar)
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) Status of this Memo 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. Copyright Notice Copyright (C) The Internet Society (1998). All Rights Reserved. Abstract 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. This memo is formatted as a registration for a MIME media type per [RFC 2048]. However, the format in this memo is equally applicable for use outside of a MIME message content type. 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. 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. 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. 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. Table of Contents 1 Introduction.....................................................5 2 Basic Grammar and Conventions....................................6 2.1 Formatting Conventions .......................................7 2.2 Related Memos ................................................8 2.3 International Considerations .................................8 3 Registration Information.........................................8 3.1 Content Type .................................................8 3.2 Parameters ...................................................9 3.3 Content Header Fields .......................................10 3.4 Encoding Considerations .....................................10 3.5 Security Considerations .....................................10 3.6 Interoperability Considerations .............................11 3.7 Applications Which Use This Media Type ......................11 3.8 Additional Information ......................................11 3.9 Magic Numbers ...............................................11 3.10 File Extensions ............................................11 3.11 Contact for Further Information: ...........................12 3.12 Intended Usage .............................................12 3.13 Authors/Change Controllers .................................12 4 iCalendar Object Specification..................................13 4.1 Content Lines ...............................................13 4.1.1 List and Field Separators ................................16 4.1.2 Multiple Values ..........................................16 4.1.3 Binary Content ...........................................16
4.1.4 Character Set ............................................17
4.2 Property Parameters .........................................17
4.2.1 Alternate Text Representation ............................18
4.2.2 Common Name ..............................................19
4.2.3 Calendar User Type .......................................20
4.2.4 Delegators ...............................................20
4.2.5 Delegatees ...............................................21
4.2.6 Directory Entry Reference ................................21
4.2.7 Inline Encoding ..........................................22
4.2.8 Format Type ..............................................23
4.2.9 Free/Busy Time Type ......................................23
4.2.10 Language ................................................24
4.2.11 Group or List Membership ................................25
4.2.12 Participation Status ....................................25
4.2.13 Recurrence Identifier Range .............................27
4.2.14 Alarm Trigger Relationship ..............................27
4.2.15 Relationship Type .......................................28
4.2.16 Participation Role ......................................29
4.2.17 RSVP Expectation ........................................29
4.2.18 Sent By .................................................30
4.2.19 Time Zone Identifier ....................................30
4.2.20 Value Data Types ........................................32
4.3 Property Value Data Types ...................................32
4.3.1 Binary ...................................................33
4.3.2 Boolean ..................................................33
4.3.3 Calendar User Address ....................................34
4.3.4 Date .....................................................34
4.3.5 Date-Time ................................................35
4.3.6 Duration .................................................37
4.3.7 Float ....................................................38
4.3.8 Integer ..................................................38
4.3.9 Period of Time ...........................................39
4.3.10 Recurrence Rule .........................................40
4.3.11 Text ....................................................45
4.3.12 Time ....................................................47
4.3.13 URI .....................................................49
4.3.14 UTC Offset ..............................................49
4.4 iCalendar Object ............................................50
4.5 Property ....................................................51
4.6 Calendar Components .........................................51
4.6.1 Event Component ..........................................52
4.6.2 To-do Component ..........................................55
4.6.3 Journal Component ........................................56
4.6.4 Free/Busy Component ......................................58
4.6.5 Time Zone Component ......................................60
4.6.6 Alarm Component ..........................................67
4.7 Calendar Properties .........................................73
4.7.1 Calendar Scale ...........................................73
4.7.2 Method ...................................................74
4.7.3 Product Identifier .......................................75
4.7.4 Version ..................................................76
4.8 Component Properties ........................................77
4.8.1 Descriptive Component Properties .........................77
4.8.1.1 Attachment ...........................................77
4.8.1.2 Categories ...........................................78
4.8.1.3 Classification .......................................79
4.8.1.4 Comment ..............................................80
4.8.1.5 Description ..........................................81
4.8.1.6 Geographic Position ..................................82
4.8.1.7 Location .............................................84
4.8.1.8 Percent Complete .....................................85
4.8.1.9 Priority .............................................85
4.8.1.10 Resources ...........................................87
4.8.1.11 Status ..............................................88
4.8.1.12 Summary .............................................89
4.8.2 Date and Time Component Properties .......................90
4.8.2.1 Date/Time Completed ..................................90
4.8.2.2 Date/Time End ........................................91
4.8.2.3 Date/Time Due ........................................92
4.8.2.4 Date/Time Start ......................................93
4.8.2.5 Duration .............................................94
4.8.2.6 Free/Busy Time .......................................95
4.8.2.7 Time Transparency ....................................96
4.8.3 Time Zone Component Properties ...........................97
4.8.3.1 Time Zone Identifier .................................97
4.8.3.2 Time Zone Name .......................................98
4.8.3.3 Time Zone Offset From ................................99
4.8.3.4 Time Zone Offset To .................................100
4.8.3.5 Time Zone URL .......................................101
4.8.4 Relationship Component Properties .......................102
4.8.4.1 Attendee ............................................102
4.8.4.2 Contact .............................................104
4.8.4.3 Organizer ...........................................106
4.8.4.4 Recurrence ID .......................................107
4.8.4.5 Related To ..........................................109
4.8.4.6 Uniform Resource Locator ............................110
4.8.4.7 Unique Identifier ...................................111
4.8.5 Recurrence Component Properties .........................112
4.8.5.1 Exception Date/Times ................................112
4.8.5.2 Exception Rule ......................................114
4.8.5.3 Recurrence Date/Times ...............................115
4.8.5.4 Recurrence Rule .....................................117
4.8.6 Alarm Component Properties ..............................126
4.8.6.1 Action ..............................................126
4.8.6.2 Repeat Count ........................................126
4.8.6.3 Trigger .............................................127
4.8.7 Change Management Component Properties ..................129
4.8.7.1 Date/Time Created ...................................129
4.8.7.2 Date/Time Stamp .....................................130
4.8.7.3 Last Modified .......................................131
4.8.7.4 Sequence Number .....................................131
4.8.8 Miscellaneous Component Properties ......................133
4.8.8.1 Non-standard Properties .............................133
4.8.8.2 Request Status ......................................134
5 iCalendar Object Examples......................................136
6 Recommended Practices..........................................140
7 Registration of Content Type Elements..........................141
7.1 Registration of New and Modified iCalendar Object Methods ..141
7.2 Registration of New Properties .............................141
7.2.1 Define the property .....................................142
7.2.2 Post the Property definition ............................143
7.2.3 Allow a comment period ..................................143
7.2.4 Submit the property for approval ........................143
7.3 Property Change Control ....................................143
8 References.....................................................144
9 Acknowledgments................................................145
10 Authors' and Chairs' Addresses................................146
11 Full Copyright Statement......................................148
1 Introduction
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.
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
unwired transport such as infrared might also be used. 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]. The memo also includes a formal grammar for the content type based on the Internet ABNF defined in [RFC 2234]. 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. 2 Basic Grammar and Conventions 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 [RFC 2119]. This memo makes use of both a descriptive prose and a more formal notation for defining the calendaring and scheduling format. The notation used in this memo is the ABNF notation of [RFC 2234]. 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. All numeric and hexadecimal values used in this memo are given in decimal notation. 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. 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.
The format for the iCalendar object is based on the syntax of the [RFC 2425] content type. While the iCalendar object is not a profile of the [RFC 2425] content type, it does reuse a number of the elements from the [RFC 2425] specification. 2.1 Formatting Conventions 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. 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.
2.2 Related Memos 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. [ITIP] - specifies an interoperability protocol for scheduling between different implementations; [IMIP] specifies an Internet email binding for [ITIP]. 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. 2.3 International Considerations 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. 3 Registration Information 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. 3.1 Content Type The following text is intended to register this memo as the MIME content type "text/calendar". To: ietf-types@uninett.no Subject: Registration of MIME content type text/calendar. MIME media type name: text MIME subtype name: calendar
3.2 Parameters Required parameters: none Optional parameters: charset, method, component and optinfo The "charset" parameter is defined in [RFC 2046] for other body parts. It is used to identify the default character set used within the body part. 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. The value for the "method" parameter is defined as follows: method = 1*(ALPHA / DIGIT / "-") ; IANA registered iCalendar object method 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. The value for the "component" parameter is defined as follows: component = ("VEVENT" / "VTODO" / "VJOURNAL" / "VFREEBUSY" / "VTIMEZONE" / x-name / iana-token) 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.
The parameter can be specified multiple times.
This parameter MAY only specify semantics already specified by the
iCalendar object and that can be otherwise determined by parsing the
body part.
The value for the "optinfo" parameter is defined as follows:
optinfo = infovalue / qinfovalue
infovalue = iana-token / x-name
qinfovalue = DQUOTE (infovalue) DQUOTE
3.3 Content Header Fields
Optional content header fields: Any header fields defined by [RFC
2045].
3.4 Encoding Considerations
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.
3.5 Security Considerations
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".
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. ATTACHMENTS - - An iCalendar object can include references to Uniform Resource Locators that can be programmed resources. 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. 3.6 Interoperability Considerations 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. 3.7 Applications Which Use This Media Type 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. 3.8 Additional Information This memo defines this content-type. 3.9 Magic Numbers None. 3.10 File Extensions 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.
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. 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. 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. 3.11 Contact for Further Information: Frank Dawson 6544 Battleford Drive Raleigh, NC 27613-3502 919-676-9515 (Telephone) 919-676-9564 (Data/Facsimile) Frank_Dawson@Lotus.com (Internet Mail) Derik Stenerson One Microsoft Way Redmond, WA 98052-6399 425-936-5522 (Telephone) 425-936-7329 (Facsimile) deriks@microsoft.com (Internet Mail) 3.12 Intended Usage COMMON 3.13 Authors/Change Controllers Frank Dawson 6544 Battleford Drive Raleigh, NC 27613-3502 919-676-9515 (Telephone) 919-676-9564 (Data/Facsimile) Frank_Dawson@Lotus.com (Internet Mail) Derik Stenerson One Microsoft Way Redmond, WA 98052-6399 425-936-5522 (Telephone) 425-936-7329 (Facsimile) deriks@microsoft.com (Internet Mail)
4 iCalendar Object Specification 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. 4.1 Content Lines 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). 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. For example the line: DESCRIPTION:This is a long description that exists on a long line. Can be represented as: DESCRIPTION:This is a lo ng description that exists on a long line. 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. 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.
The content information associated with an iCalendar object is formatted using a syntax similar to that defined by [RFC 2425]. That is, the content information consists of CRLF-separated content lines. The following notation defines the lines of content in an iCalendar object: 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
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.
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.
4.1.1 List and Field Separators 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). 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). 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). Property parameters with values containing a COLON, a SEMICOLON or a COMMA character MUST be placed in quoted text. 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. ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:MAILTO: jsmith@host.com RDATE;VALUE=DATE:19970304,19970504,19970704,19970904 4.1.2 Multiple Values 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. 4.1.3 Binary Content 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
can be included within an iCalendar object, but only after first encoding it into text using the "BASE64" encoding method defined in [RFC 2045]. 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). The following example specifies an "ATTACH" property that references an attachment external to the iCalendar object with a URI reference: ATTACH:http://xyz.com/public/quarterly-report.doc The following example specifies an "ATTACH" property with inline binary encoded content information: ATTACH;FMTTYPE=image/basic;ENCODING=BASE64;VALUE=BINARY: MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1U EBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIE <...remainder of "BASE64" encoded binary data...> 4.1.4 Character Set 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 [RFC 2279]. The "charset" Content-Type parameter can be used in MIME transports to specify any other IANA registered character set. 4.2 Property Parameters 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. 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:
DESCRIPTION;ALTREP="http://www.wiz.org":The Fall'98 Wild Wizards
Conference - - Las Vegas, NV, USA
Property parameter values that are not in quoted strings are case
insensitive.
The general property parameters defined by this memo are defined by
the following notation:
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)
4.2.1 Alternate Text Representation
Parameter Name: ALTREP
Purpose: To specify an alternate text representation for the property
value.
Format Definition: The property parameter is defined by the following
notation:
altrepparam = "ALTREP" "=" DQUOTE uri DQUOTE
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.
Example:
DESCRIPTION;ALTREP="CID:<part3.msg.970415T083000@host.com>":Project
XYZ Review Meeting will include the following agenda items: (a)
Market Overview, (b) Finances, (c) Project Management
The "ALTREP" property parameter value might point to a "text/html"
content portion.
Content-Type:text/html
Content-Id:<part3.msg.970415T083000@host.com>
<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>
4.2.2 Common Name
Parameter Name: CN
Purpose: To specify the common name to be associated with the
calendar user specified by the property.
Format Definition: The property parameter is defined by the following
notation:
cnparam = "CN" "=" param-value
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.
Example:
ORGANIZER;CN="John Smith":MAILTO:jsmith@host.com
4.2.3 Calendar User Type
Parameter Name: CUTYPE
Purpose: To specify the type of calendar user specified by the
property.
Format Definition: The property parameter is defined by the following
notation:
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
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.
Example:
ATTENDEE;CUTYPE=GROUP:MAILTO:ietf-calsch@imc.org
4.2.4 Delegators
Parameter Name: DELEGATED-FROM
Purpose: To specify the calendar users that have delegated their
participation to the calendar user specified by the property.
Format Definition: The property parameter is defined by the following
notation:
delfromparam = "DELEGATED-FROM" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
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 [RFC 1738]. The individual calendar address parameter values MUST each be specified in a quoted-string. Example: ATTENDEE;DELEGATED-FROM="MAILTO:jsmith@host.com":MAILTO: jdoe@host.com 4.2.5 Delegatees Parameter Name: DELEGATED-TO Purpose: To specify the calendar users to whom the calendar user specified by the property has delegated participation. Format Definition: The property parameter is defined by the following notation: deltoparam = "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE *("," DQUOTE cal-address DQUOTE) Description: This parameter can be specified on properties with a CAL-ADDRESS value type. This parameter specifies those calendar users whom have been delegated participation in a group scheduled event or to-do by the calendar user specified by the property. The value MUST be a MAILTO URI as defined in [RFC 1738]. The individual calendar address parameter values MUST each be specified in a quoted-string. Example: ATTENDEE;DELEGATED-TO="MAILTO:jdoe@host.com","MAILTO:jqpublic@ host.com":MAILTO:jsmith@host.com 4.2.6 Directory Entry Reference Parameter Name: DIR Purpose: To specify reference to a directory entry associated with the calendar user specified by the property. Format Definition: The property parameter is defined by the following notation:
dirparam = "DIR" "=" DQUOTE uri DQUOTE
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies a reference to the
directory entry associated with the calendar user specified by the
property. The parameter value is a URI. The individual URI parameter
values MUST each be specified in a quoted-string.
Example:
ORGANIZER;DIR="ldap://host.com:6666/o=eDABC%20Industries,c=3DUS??
(cn=3DBJim%20Dolittle)":MAILTO:jimdo@host1.com
4.2.7 Inline Encoding
Parameter Name: ENCODING
Purpose: To specify an alternate inline encoding for the property
value.
Format Definition: The property parameter is defined by the following
notation:
encodingparam = "ENCODING" "="
("8BIT"
; "8bit" text encoding is defined in [RFC 2045]
/ "BASE64"
; "BASE64" binary encoding format is defined in [RFC 2045]
/ iana-token
; Some other IANA registered iCalendar encoding type
/ x-name)
; A non-standard, experimental encoding type
Description: The property parameter identifies the inline encoding
used in a property value. The default encoding is "8BIT",
corresponding to a property value consisting of text. The "BASE64"
encoding type corresponds to a property value encoded using the
"BASE64" encoding defined in [RFC 2045].
If the value type parameter is ";VALUE=BINARY", then the inline
encoding parameter MUST be specified with the value
";ENCODING=BASE64".
Example:
ATTACH;FMTYPE=IMAGE/JPEG;ENCODING=BASE64;VALUE=BINARY:MIICajC
CAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDA
qBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRw
<...remainder of "BASE64" encoded binary data...>
4.2.8 Format Type
Parameter Name: FMTTYPE
Purpose: To specify the content type of a referenced object.
Format Definition: The property parameter is defined by the following
notation:
fmttypeparam = "FMTTYPE" "=" iana-token
; A IANA registered content type
/ x-name
; A non-standard content type
Description: This parameter can be specified on properties that are
used to reference an object. The parameter specifies the content type
of the referenced object. For example, on the "ATTACH" property, a
FTP type URI value does not, by itself, necessarily convey the type
of content associated with the resource. The parameter value MUST be
the TEXT for either an IANA registered content type or a non-standard
content type.
Example:
ATTACH;FMTTYPE=application/binary:ftp://domain.com/pub/docs/
agenda.doc
4.2.9 Free/Busy Time Type
Parameter Name: FBTYPE
Purpose: To specify the free or busy time type.
Format Definition: The property parameter is defined by the following
notation:
fbtypeparam = "FBTYPE" "=" ("FREE" / "BUSY"
/ "BUSY-UNAVAILABLE" / "BUSY-TENTATIVE"
/ x-name
; Some experimental iCalendar data type.
/ iana-token)
; Some other IANA registered iCalendar data type.
Description: The parameter specifies the free or busy time type. The
value FREE indicates that the time interval is free for scheduling.
The value BUSY indicates that the time interval is busy because one
or more events have been scheduled for that interval. The value
BUSY-UNAVAILABLE indicates that the time interval is busy and that
the interval can not be scheduled. The value BUSY-TENTATIVE indicates
that the time interval is busy because one or more events have been
tentatively scheduled for that interval. If not specified on a
property that allows this parameter, the default is BUSY.
Example: The following is an example of this parameter on a FREEBUSY
property.
FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z
4.2.10 Language
Parameter Name: LANGUAGE
Purpose: To specify the language for text values in a property or
property parameter.
Format Definition: The property parameter is defined by the following
notation:
languageparam = "LANGUAGE" "=" language
language = <Text identifying a language, as defined in [RFC 1766]>
Description: This parameter can be specified on properties with a
text value type. The parameter identifies the language of the text in
the property or property parameter value. The value of the "language"
property parameter is that defined in [RFC 1766].
For transport in a MIME entity, the Content-Language header field can
be used to set the default language for the entire body part.
Otherwise, no default language is assumed.
Example:
SUMMARY;LANGUAGE=us-EN:Company Holiday Party
LOCATION;LANGUAGE=en:Germany
LOCATION;LANGUAGE=no:Tyskland
The following example makes use of the Quoted-Printable encoding in
order to represent non-ASCII characters.
LOCATION;LANGUAGE=da:K=F8benhavn
LOCATION;LANGUAGE=en:Copenhagen
4.2.11 Group or List Membership
Parameter Name: MEMBER
Purpose: To specify the group or list membership of the calendar user
specified by the property.
Format Definition: The property parameter is defined by the following
notation:
memberparam = "MEMBER" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the groups or list
membership for the calendar user specified by the property. The
parameter value either a single calendar address in a quoted-string
or a COMMA character (US-ASCII decimal 44) list of calendar
addresses, each in a quoted-string. The individual calendar address
parameter values MUST each be specified in a quoted-string.
Example:
ATTENDEE;MEMBER="MAILTO:ietf-calsch@imc.org":MAILTO:jsmith@host.com
ATTENDEE;MEMBER="MAILTO:projectA@host.com","MAILTO:projectB@host.
com":MAILTO:janedoe@host.com
4.2.12 Participation Status
Parameter Name: PARTSTAT
Purpose: To specify the participation status for the calendar user
specified by the property.
Format Definition: The property parameter is defined by the following
notation:
partstatparam = "PARTSTAT" "="
("NEEDS-ACTION" ; Event needs action
/ "ACCEPTED" ; Event accepted
/ "DECLINED" ; Event declined
/ "TENTATIVE" ; Event tentatively
; accepted
/ "DELEGATED" ; Event delegated
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered
; status
; These are the participation statuses for a "VEVENT". Default is
; NEEDS-ACTION
partstatparam /= "PARTSTAT" "="
("NEEDS-ACTION" ; To-do needs action
/ "ACCEPTED" ; To-do accepted
/ "DECLINED" ; To-do declined
/ "TENTATIVE" ; To-do tentatively
; accepted
/ "DELEGATED" ; To-do delegated
/ "COMPLETED" ; To-do completed.
; COMPLETED property has
;date/time completed.
/ "IN-PROCESS" ; To-do in process of
; being completed
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered
; status
; These are the participation statuses for a "VTODO". Default is
; NEEDS-ACTION
partstatparam /= "PARTSTAT" "="
("NEEDS-ACTION" ; Journal needs action
/ "ACCEPTED" ; Journal accepted
/ "DECLINED" ; Journal declined
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered
; status
; These are the participation statuses for a "VJOURNAL". Default is
; NEEDS-ACTION
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the participation
status for the calendar user specified by the property value. The
parameter values differ depending on whether they are associated with
a group scheduled "VEVENT", "VTODO" or "VJOURNAL". The values MUST
match one of the values allowed for the given calendar component. If
not specified on a property that allows this parameter, the default
value is NEEDS-ACTION.
Example:
ATTENDEE;PARTSTAT=DECLINED:MAILTO:jsmith@host.com
4.2.13 Recurrence Identifier Range Parameter Name: RANGE Purpose: To specify the effective range of recurrence instances from the instance specified by the recurrence identifier specified by the property. Format Definition: The property parameter is defined by the following notation: rangeparam = "RANGE" "=" ("THISANDPRIOR" ; To specify all instances prior to the recurrence identifier / "THISANDFUTURE") ; To specify the instance specified by the recurrence identifier ; and all subsequent recurrence instances Description: The parameter can be specified on a property that specifies a recurrence identifier. The parameter specifies the effective range of recurrence instances that is specified by the property. The effective range is from the recurrence identified specified by the property. If this parameter is not specified an allowed property, then the default range is the single instance specified by the recurrence identifier value of the property. The parameter value can be "THISANDPRIOR" to indicate a range defined by the recurrence identified value of the property and all prior instances. The parameter value can also be "THISANDFUTURE" to indicate a range defined by the recurrence identifier and all subsequent instances. Example: RECURRENCE-ID;RANGE=THISANDPRIOR:19980401T133000Z 4.2.14 Alarm Trigger Relationship Parameter Name: RELATED Purpose: To specify the relationship of the alarm trigger with respect to the start or end of the calendar component. Format Definition: The property parameter is defined by the following notation: trigrelparam = "RELATED" "=" ("START" ; Trigger off of start / "END") ; Trigger off of end
Description: The parameter can be specified on properties that
specify an alarm trigger with a DURATION value type. The parameter
specifies whether the alarm will trigger relative to the start or end
of the calendar component. The parameter value START will set the
alarm to trigger off the start of the calendar component; the
parameter value END will set the alarm to trigger off the end of the
calendar component. If the parameter is not specified on an allowable
property, then the default is START.
Example:
TRIGGER;RELATED=END:PT5M
4.2.15 Relationship Type
Parameter Name: RELTYPE
Purpose: To specify the type of hierarchical relationship associated
with the calendar component specified by the property.
Format Definition: The property parameter is defined by the following
notation:
reltypeparam = "RELTYPE" "="
("PARENT" ; Parent relationship. Default.
/ "CHILD" ; Child relationship
/ "SIBLING ; Sibling relationship
/ iana-token ; Some other IANA registered
; iCalendar relationship type
/ x-name) ; A non-standard, experimental
; relationship type
Description: This parameter can be specified on a property that
references another related calendar. The parameter specifies the
hierarchical relationship type of the calendar component referenced
by the property. The parameter value can be PARENT, to indicate that
the referenced calendar component is a superior of calendar
component; CHILD to indicate that the referenced calendar component
is a subordinate of the calendar component; SIBLING to indicate that
the referenced calendar component is a peer of the calendar
component. If this parameter is not specified on an allowable
property, the default relationship type is PARENT.
Example:
RELATED-TO;RELTYPE=SIBLING:<19960401-080045-4000F192713@host.com>
4.2.16 Participation Role Parameter Name: ROLE Purpose: To specify the participation role for the calendar user specified by the property. Format Definition: The property parameter is defined by the following notation: roleparam = "ROLE" "=" ("CHAIR" ; Indicates chair of the ; calendar entity / "REQ-PARTICIPANT" ; Indicates a participant whose ; participation is required / "OPT-PARTICIPANT" ; Indicates a participant whose ; participation is optional / "NON-PARTICIPANT" ; Indicates a participant who is ; copied for information ; purposes only / x-name ; Experimental role / iana-token) ; Other IANA role ; Default is REQ-PARTICIPANT Description: This parameter can be specified on properties with a CAL-ADDRESS value type. The parameter specifies the participation role for the calendar user specified by the property in the group schedule calendar component. If not specified on a property that allows this parameter, the default value is REQ-PARTICIPANT. Example: ATTENDEE;ROLE=CHAIR:MAILTO:mrbig@host.com 4.2.17 RSVP Expectation Parameter Name: RSVP Purpose: To specify whether there is an expectation of a favor of a reply from the calendar user specified by the property value. Format Definition: The property parameter is defined by the following notation: rsvpparam = "RSVP" "=" ("TRUE" / "FALSE") ; Default is FALSE
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the expectation of a
reply from the calendar user specified by the property value. This
parameter is used by the "Organizer" to request a participation
status reply from an "Attendee" of a group scheduled event or to-do.
If not specified on a property that allows this parameter, the
default value is FALSE.
Example:
ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host.com
4.2.18 Sent By
Parameter Name: SENT-BY
Purpose: To specify the calendar user that is acting on behalf of the
calendar user specified by the property.
Format Definition: The property parameter is defined by the following
notation:
sentbyparam = "SENT-BY" "=" DQUOTE cal-address DQUOTE
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the calendar user
that is acting on behalf of the calendar user specified by the
property. The parameter value MUST be a MAILTO URI as defined in [RFC
1738]. The individual calendar address parameter values MUST each be
specified in a quoted-string.
Example:
ORGANIZER;SENT-BY:"MAILTO:sray@host.com":MAILTO:jsmith@host.com
4.2.19 Time Zone Identifier
Parameter Name: TZID
Purpose: To specify the identifier for the time zone definition for a
time component in the property value.
Format Definition: This property parameter is defined by the
following notation:
tzidparam = "TZID" "=" [tzidprefix] paramtext CRLF
tzidprefix = "/"
Description: The parameter MUST be specified on the "DTSTART",
"DTEND", "DUE", "EXDATE" and "RDATE" properties when either a DATE-
TIME or TIME value type is specified and when the value is not either
a UTC or a "floating" time. Refer to the DATE-TIME or TIME value type
definition for a description of UTC and "floating time" formats. This
property parameter specifies a text value which uniquely identifies
the "VTIMEZONE" calendar component to be used when evaluating the
time portion of the property. The value of the TZID property
parameter will be equal to the value of the TZID property for the
matching time zone definition. An individual "VTIMEZONE" calendar
component MUST be specified for each unique "TZID" parameter value
specified in the iCalendar object.
The parameter MUST be specified on properties with a DATE-TIME value
if the DATE-TIME is not either a UTC or a "floating" time.
The presence of the SOLIDUS character (US-ASCII decimal 47) as a
prefix, indicates that this TZID represents a unique ID in a globally
defined time zone registry (when such registry is defined).
Note: This document does not define a naming convention for time
zone identifiers. Implementers may want to use the naming
conventions defined in existing time zone specifications such as
the public-domain Olson database [TZ]. The specification of
globally unique time zone identifiers is not addressed by this
document and is left for future study.
The following are examples of this property parameter:
DTSTART;TZID=US-Eastern:19980119T020000
DTEND;TZID=US-Eastern:19980119T030000
The TZID property parameter MUST NOT be applied to DATE-TIME or TIME
properties whose time values are specified in UTC.
The use of local time in a DATE-TIME or TIME value without the TZID
property parameter is to be interpreted as a local time value,
regardless of the existence of "VTIMEZONE" calendar components in the
iCalendar object.
For more information see the sections on the data types DATE-TIME and
TIME.
4.2.20 Value Data Types Parameter Name: VALUE Purpose: To explicitly specify the data type format for a property value. Format Definition: The "VALUE" property parameter is defined by the following notation: valuetypeparam = "VALUE" "=" valuetype valuetype = ("BINARY" / "BOOLEAN" / "CAL-ADDRESS" / "DATE" / "DATE-TIME" / "DURATION" / "FLOAT" / "INTEGER" / "PERIOD" / "RECUR" / "TEXT" / "TIME" / "URI" / "UTC-OFFSET" / x-name ; Some experimental iCalendar data type. / iana-token) ; Some other IANA registered iCalendar data type. Description: The parameter specifies the data type and format of the property value. The property values MUST be of a single value type. For example, a "RDATE" property cannot have a combination of DATE- TIME and TIME value types. If the property's value is the default value type, then this parameter need not be specified. However, if the property's default value type is overridden by some other allowable value type, then this parameter MUST be specified.
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