Internet DRAFT - draft-royer-itip-basic
draft-royer-itip-basic
Network Working Group D. Royer
Internet-Draft IntelliCal, LLC
Expires: October 2, 2005 April 3, 2005
Basic iCalendar Transport-Independent Interoperability Protocol
(iTIP) Scheduling Events
draft-royer-itip-basic-00
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 2, 2005.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This is the second release of iTIP. After having learned from
RFC-2446 where most of this text comes from. This document
represents the common objects needed for basic calendaring. The
VTODO, VJOURNAL, VTIMEZONE, recurrence rules (RDATE remains), and
scheduling and their associated properties have been removed. These
removals are expected to appear in new memos at a later time and will
be independent extensions of this specification. The new EXTENSIONS
Royer Expires October 2, 2005 [Page 1]
Internet-Draft iTIPbis April 2005
property will exist to allow for compatible sets of extensions.
This document specifies how calendaring systems use iCalendar objects
to interoperate with other calendar systems. It does so in a general
way so as to allow multiple methods of communication between systems.
Subsequent documents specify interoperable methods of communications
between systems that use this protocol.
The document outlines a model for calendar exchange that defines both
static and dynamic event, to-do, journal and free/busy objects.
Static objects are used to transmit information from one entity to
another without the expectation of continuity or referential
integrity with the original item. Dynamic objects are a superset of
static objects and will gracefully degrade to their static
counterparts for clients that only support static objects.
This document specifies an Internet protocol based on the iCalendar
object specification that provides scheduling interoperability
between different calendar systems. The Internet protocol is called
the "Basic iCalendar Transport-Independent Interoperability Protocol
(iTIP-Basic)". iTIP-Basic complements the iCalendar object
specification by adding semantics for group scheduling methods
commonly available in current calendar systems. These scheduling
methods permit two or more calendar systems to perform transactions
such as publish, schedule, reschedule, respond to scheduling
requests, negotiation of changes or cancel iCalendar-based calendar
components.
iTIP-Basic is defined independent of the particular transport used to
transmit the scheduling information. Companion memos to iTIP-Basic
provide bindings of the interoperability protocol to a number of
Internet protocols.
Royer Expires October 2, 2005 [Page 2]
Internet-Draft iTIPbis April 2005
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Formatting Conventions . . . . . . . . . . . . . . . . . . 4
1.2 Related Documents . . . . . . . . . . . . . . . . . . . . 5
1.3 ITIP-BASIC Roles and Transactions . . . . . . . . . . . . 5
2. Interoperability Models . . . . . . . . . . . . . . . . . . . 8
2.1 Application Protocol . . . . . . . . . . . . . . . . . . . 8
2.1.1 Calendar Entry State . . . . . . . . . . . . . . . . . 9
2.1.2 Delegation . . . . . . . . . . . . . . . . . . . . . . 9
2.1.3 Acting on Behalf of other Calendar Users . . . . . . . 9
2.1.4 Component Revisions . . . . . . . . . . . . . . . . . 10
2.1.5 Message Sequencing . . . . . . . . . . . . . . . . . . 10
3. Application Protocol Elements . . . . . . . . . . . . . . . . 12
3.1 Common Component Restriction Tables . . . . . . . . . . . 12
3.2 Methods for VEVENT Calendar Components . . . . . . . . . . 13
3.2.1 PUBLISH . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.2 REQUEST . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.3 REPLY . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2.4 ADD . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2.5 CANCEL . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.6 REFRESH . . . . . . . . . . . . . . . . . . . . . . . 25
3.2.7 COUNTER . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.8 DECLINECOUNTER . . . . . . . . . . . . . . . . . . . . 27
3.3 Methods For VFREEBUSY Components . . . . . . . . . . . . . 28
3.3.1 PUBLISH . . . . . . . . . . . . . . . . . . . . . . . 29
3.3.2 REQUEST . . . . . . . . . . . . . . . . . . . . . . . 30
3.3.3 REPLY . . . . . . . . . . . . . . . . . . . . . . . . 31
3.4 Methods For VTODO Components . . . . . . . . . . . . . . . 32
3.5 Methods For VJOURNAL Components . . . . . . . . . . . . . 32
3.6 Status Replies . . . . . . . . . . . . . . . . . . . . . . 32
3.7 Implementation Considerations . . . . . . . . . . . . . . 35
3.7.1 Working With Recurrence Instances . . . . . . . . . . 35
3.7.2 Attendee Property Considerations . . . . . . . . . . . 35
3.7.3 X-Tokens . . . . . . . . . . . . . . . . . . . . . . . 35
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5. Application Protocol Fallbacks . . . . . . . . . . . . . . . . 37
5.1 Partial Implementation . . . . . . . . . . . . . . . . . . 37
5.1.1 Event-Related Fallbacks . . . . . . . . . . . . . . . 37
5.1.2 Latency Issues . . . . . . . . . . . . . . . . . . . . 37
5.1.3 Sequence Number . . . . . . . . . . . . . . . . . . . 37
5.2 Security Considerations . . . . . . . . . . . . . . . . . 37
5.2.1 Security Threats . . . . . . . . . . . . . . . . . . . 38
5.2.2 Recommendations . . . . . . . . . . . . . . . . . . . 39
5.3 Acknowledgments . . . . . . . . . . . . . . . . . . . . . 40
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 41
Intellectual Property and Copyright Statements . . . . . . . . 42
Royer Expires October 2, 2005 [Page 3]
Internet-Draft iTIPbis April 2005
1. Introduction
This document specifies how calendaring systems use iCalendar objects
to interoperate with other calendar systems. In particular, it
specifies how to schedule events only. To-dos, or daily journal
entries have been removed. It further specifies how to ask for
available busy time information. It does so in a general way so as
to allow multiple methods of communication between systems.
Subsequent documents specify transport bindings between systems that
use this protocol.
This protocol is based on messages sent from an originator to one or
more recipients. For certain types of messages, a recipient may
reply, in order to update their status and may also return
transaction/request status information. The protocol supports the
ability for the message originator to modify or cancel the original
message. The protocol also supports the ability for recipients to
suggest changes to the originator of a message. The elements of the
protocol also define the user roles for its transactions.
1.1 Formatting Conventions
In order to refer to elements of the calendaring and scheduling
model, core object or interoperability protocol defined in [1] and
[iTIP-Basic] several formatting conventions have been utilized.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
document are to be interpreted as described in [3].
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" (CU)
within the scheduling protocol defined by [iTIP-Basic]. Calendar
components defined by [1] 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. Scheduling methods defined by [iTIP-Basic] 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.
Properties defined by [1] 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
Royer Expires October 2, 2005 [Page 4]
Internet-Draft iTIPbis April 2005
parameters defined by this memo are referred to with lower case,
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".
In tables, the quoted-string text is specified without quotes in
order to minimize the table length.
1.2 Related Documents
Implementers will need to be familiar with several other memos that,
along with this one, describe the Internet calendaring and scheduling
standards. This document, [iTIP-Basic], specifies an
interoperability protocol for scheduling between different
implementations. The related documents are:
[1] - specifies the objects, data types, properties and property
parameters used in the protocols, along with the methods for
representing and encoding them;
[2] specifies an Internet email binding for [iTIP-Basic].
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.
1.3 ITIP-BASIC Roles and Transactions
ITIP-BASIC defines methods for exchanging [1] objects for the
purposes of group calendaring and scheduling between "Calendar Users"
(CUs). CUs take on one of two roles in iTIP-Basic. The CU who
initiates an exchange takes on the role of "Organizer". For example,
the CU who proposes a group meeting is the "Organizer". The CUs
asked to participate in the group meeting by the "Organizer" take on
the role of "Attendee". Note that "role" is also a descriptive
parameter to the _ATTENDEE_ property. Its use is to convey
descriptive context to an "Attendee" such as "chair",
"req-participant" or "non-participant" and has nothing to do with the
calendaring workflow.
The ITIP-BASIC methods are listed below and their usage and semantics
are defined in section 3 of this document.
Royer Expires October 2, 2005 [Page 5]
Internet-Draft iTIPbis April 2005
+================+==================================================+
| Method | Description |
|================+==================================================|
| PUBLISH | Used to publish a calendar entry to one or more |
| | Calendar Users. There is no interactivity |
| | between the publisher and any other calendar |
| | user. An example might include a baseball team |
| | publishing its schedule to the public. |
| | |
| REQUEST | Used to schedule a calendar entry with other |
| | Calendar Users. Requests are interactive in that |
| | they require the receiver to respond using |
| | the Reply methods. Meeting Requests, Busy |
| | Time requests. Requests are also used by the |
| | "Organizer" to |
| | update the status of a calendar entry. |
| | |
| REPLY | A Reply is used in response to a Request to |
| | convey "Attendee" status to the "Organizer". |
| | Replies are commonly used to respond to meeting |
| | and task requests. |
| | |
| ADD | The only way to add one or more instances to an |
| | existing VEVENT. |
| | |
| CANCEL | Cancel one or more instances of an existing |
| | VEVENT. |
| | |
| REFRESH | The Refresh method is used by an "Attendee" to |
| | request the latest version of a calendar entry. |
| | |
| COUNTER | The Counter method is used by an "Attendee" to |
| | ask for a change in the calendar entry. |
| | Examples include the request to change a |
| | proposed Event time. |
| | |
| DECLINE- | Used by the "Organizer" to decline the proposed |
| COUNTER | counter-proposal. |
+================+==================================================+
Group scheduling in iTIP-Basic is accomplished using the set of
"request" and "response" methods described above. The following
table shows the methods broken down by who can send them.
Royer Expires October 2, 2005 [Page 6]
Internet-Draft iTIPbis April 2005
+================+==================================================+
| Originator | Methods |
|================+==================================================|
| Organizer | PUBLISH, REQUEST, ADD, CANCEL, DECLINECOUNTER |
| | |
| Attendee | REPLY, REFRESH, COUNTER |
+================+==================================================+
Note that for some calendar component types, the allowable methods
are a subset of the above set.
Royer Expires October 2, 2005 [Page 7]
Internet-Draft iTIPbis April 2005
2. Interoperability Models
There are two distinct protocols relevant to interoperability: an
"Application Protocol" and a "Transport Protocol". The Application
Protocol defines the content of the iCalendar objects sent between
sender and receiver to accomplish the scheduling transactions listed
above. The Transport Protocol defines how the iCalendar objects are
sent between the sender and receiver. This document focuses on the
Application Protocol. Binding documents such as [2] focus on the
Transport Protocol.
The connection between Sender and Receiver in the diagram below
refers to the Application Protocol. The iCalendar objects passed
from the Sender to the Receiver are presented in Section 3,
Application Protocol Elements.
+----------+ +----------+
| | iTIP-Basic | |
| Sender |<-------------------->| Receiver |
| | | |
+----------+ +----------+
There are several variations of this diagram in which the Sender and
Receiver take on various roles of a "Calendar User Agent" (CUA) or a
"Calendar Service" (CS).
The architecture of iTIP-Basic is depicted in the diagram below. An
application written to this specification may work with bindings for
the store-and-forward transport, the real time transport, or both.
Also note that iTIP-Basic could be bound to other transports.
+------------------------------------------+
| iTIP-Basic |
+------------------------------------------+
|Real-time | Store-and-Fwd | Other |
|Transport | Transport | Transports... |
+------------------------------------------+
2.1 Application Protocol
In the iTIP-Basic model, a calendar entry is created and managed by
an "Organizer". The "Organizer" interacts with other CUs by sending
one or more of the iTIP-Basic messages listed above. "Attendees" use
the "REPLY" method to communicate their status. "Attendees" do not
make direct changes to the master calendar entry. They can, however,
use the "COUNTER" method to suggest changes to the "Organizer". In
any case, the "Organizer" has complete control over the master
Royer Expires October 2, 2005 [Page 8]
Internet-Draft iTIPbis April 2005
calendar entry.
2.1.1 Calendar Entry State
There are two distinct states relevant to calendar entries: the
overall state of the entry and the state associated with an
"Attendee" to that entry.
The state of an entry is defined by the "STATUS" property and is
controlled by the "Organizer." There is no default value for the
"STATUS" property. The "Organizer" sets the "STATUS" property to the
appropriate value for each calendar entry.
The state of a particular "Attendee" relative to an entry is defined
by the "partstat" parameter in the "ATTENDEE" property for each
"Attendee". When an "Organizer" issues the initial entry, "Attendee"
status is unknown. The "Organizer" specifies this by setting the
"partstat" parameter to "NEEDS-ACTION". Each "Attendee" modifies
their "ATTENDEE" property "partstat" parameter to an appropriate
value as part of a "REPLY" message sent back to the "Organizer".
2.1.2 Delegation
Delegation is defined as the process by which an "Attendee" grants
another CU (or several CUs) the right to attend on their behalf. The
"Organizer" is made aware of this change because the delegating
"Attendee" informs the "Organizer". These steps are detailed in the
REQUEST method section.
This is not supported in iTIP-Basic.
2.1.3 Acting on Behalf of other Calendar Users
In many organizations one user will act on behalf of another to
organize and/or respond to meeting requests. ITIP-BASIC provides two
mechanisms that support these activities.
First, the "Organizer" is treated as a special entity, separate from
"Attendees". All responses from "Attendees" flow to the "Organizer",
making it easy to separate a calendar user organizing a meeting from
calendar users attending the meeting. Additionally, iCalendar
provides descriptive roles for each "Attendee". For instance, a role
of "chair" may be ascribed to one or more "Attendees". The "chair"
and the "Organizer" may or may not be the same calendar user. This
maps well to scenarios where an assistant may manage meeting
logistics for another individual who chairs a meeting.
Second, a "sent-by" parameter may be specified in either the
Royer Expires October 2, 2005 [Page 9]
Internet-Draft iTIPbis April 2005
"Organizer" or "Attendee" properties. When specified, the "sent-by"
parameter indicates that the responding CU acted on behalf of the
specified "Attendee" or "Organizer".
2.1.4 Component Revisions
The "SEQUENCE" property is used by the "Organizer" to indicate
revisions to the calendar component. The rules for incrementing the
"SEQUENCE" number are defined in [1].]
In some circumstances the "Organizer" may not have received responses
to the final revision sent out. In this situation, the "Organizer"
may wish to send an update "REQUEST", and set "RSVP=TRUE" for all
"Attendees", so that current responses can be collected.
The value of the "SEQUENCE" property contained in a response from an
"Attendee" may not always match the "Organizer's" revision.
Implementations may choose to have the CUA indicate to the CU that
the response is to an entry that has been revised and allow the CU to
decide whether or not to accept the response.
The "Organizer" is not required to send objects to any "Attendee"
unless the change effects the "Attendee". It is possible for an
"Attendee" to get invited with an object with a sequence value larger
then zero. And it is possible for an "Attendee" to get an update
that has a "SEQUENCE" property value that is more than one larger
than what the "Attendee" currently has. As an example the
"Organizer" may determine that it will not send each "Attendee" an
update each time an new "Attendee" is added.
2.1.5 Message Sequencing
CUAs that handle the [iTIP-Basic] application protocol must often
correlate a component in a calendar store with a component received
in the [iTIP-Basic] message. For example, an event may be updated
with a later revision of the same event. To accomplish this, a CUA
must correlate the version of the event already in its calendar store
with the version sent in the [iTIP-Basic] message. In addition to
this correlation, there are several factors that can cause
[iTIP-Basic] messages to arrive in an unexpected order. That is, an
"Organizer" could receive a reply to an earlier revision of a
component AFTER receiving a reply to a later revision.
To maximize interoperability and to handle messages that arrive in an
unexpected order, use the following rules:
1. The primary key for referencing a particular iCalendar
component is the "UID" property value.
Royer Expires October 2, 2005 [Page 10]
Internet-Draft iTIPbis April 2005
2. The secondary key for referencing a component is the
"SEQUENCE" property value. For components where the "UID" is the
same, the component with the highest numeric value for the
"SEQUENCE" property obsoletes all other revisions of the component
with lower values. For an "Attendee" that means that toss the
current object and replace it with the new object, keeping any
local implementation specific information when possible.
3. "Attendees" send "REPLY" messages to the "Organizer". For
replies where the "UID" property value is the same, the value of
the "SEQUENCE" property indicates the revision of the component to
which the "Attendee" is replying. The reply with the highest
numeric value for the "SEQUENCE" property obsoletes all other
replies with lower values.
4. In situations where the "UID" and "SEQUENCE" properties match,
the "DTSTAMP" property is used as the tie-breaker. The component
with the latest "DTSTAMP" overrides all others. Similarly, for
"Attendee" responses where the "UID" property values match and the
"SEQUENCE" property values match, the response with the latest
"DTSTAMP" overrides all others.
Hence, CUAs must persist the following component properties: "UID",
"SEQUENCE", and "DTSTAMP". Furthermore, for each "ATTENDEE" property
of a component CUAs must persist the "SEQUENCE" and "DTSTAMP"
property values associated with the "Attendee's" response.
Royer Expires October 2, 2005 [Page 11]
Internet-Draft iTIPbis April 2005
3. Application Protocol Elements
ITIP-BASIC messages are "text/calendar" MIME entities that contain
calendaring and scheduling information. The particular type of [1]
message is referred to as the "method type". Each method type is
identified by a "METHOD" property specified as part of the
"text/calendar" content type. The table below shows various
combinations of calendar components and the method types that this
memo supports.
+=================================================+
| | VEVENT | VTODO | VJOURNAL | VFREEBUSY |
|=================================================|
|Publish | Yes | No | No | Yes |
|Request | Yes | No | No | Yes |
|Refresh | Yes | No | No | No |
|Cancel | Yes | No | No | No |
|Add | Yes | No | No | No |
|Reply | Yes | No | No | Yes |
|Counter | Yes | No | No | No |
|Decline- | | | | |
|Counter | Yes | No | No | No |
+=================================================+
Each method type is defined in terms of its associated components and
properties. Some components and properties are required, some are
optional and others are excluded. The restrictions are expressed in
this document using a simple "restriction table". The first column
indicates the name of a component or property. Properties of the
iCalendar object are not indented. Properties of a component are
indented. The second column contains "MUST" if the component or
property must be present, "MAY" if the component or property is
optional, and "NOT" if the component or property must not be present.
Entries in the second column sometimes contain comments for further
clarification.
3.1 Common Component Restriction Tables
The restriction table below applies to properties of the iCalendar
object. That is, the properties at the outermost scope. The
presence column uses the following values to assert whether a
property is required, is optional and the number of times it may
appear in the iCalendar object.
Royer Expires October 2, 2005 [Page 12]
Internet-Draft iTIPbis April 2005
Presence Value Description
--------------------------------------------------------------
1 One instance MUST be present
1+ At least one instance MUST be present
0 Instances of this property Must NOT be present
0+ Multiple instances MAY be present
0 or 1 Up to 1 instance of this property MAY be present
---------------------------------------------------------------
The tables also call out "X-PROPERTY" and "X-COMPONENT" to show
where vendor-specific properties and components can appear. The
tables do not lay out the restrictions of property parameters. Those
restrictions are defined in [1].
Component/Property Presence
------------------- ----------------------------------------------
CALSCALE 0 or 1 If '0', the object is GREGORIAN.
PRODID 1
VERSION 1 Value MUST be "2.0"
X-PROPERTY 0+
DateTime values MUST NOT refer to a "VTIMEZONE" component.
Component/Property Presence
------------------- ----------------------------------------------
VTIMEZONE 0 MUST NOT be present as iCal-Basic does
not support time zones.
The property restrictions in the table below apply to any "VALARM"
component in an ITIP-BASIC message.
Component/Property Presence
------------------- ----------------------------------------------
VALARM 0+
ACTION 1
ATTACH 0+
DESCRIPTION 0 or 1
DURATION 0 or 1 if present REPEAT MUST be present
REPEAT 0 or 1 if present DURATION MUST be present
SUMMARY 0 or 1
TRIGGER 1
X-PROPERTY 0+
3.2 Methods for VEVENT Calendar Components
This section defines the property set restrictions for the method
types that are applicable to the "VEVENT" calendar component. Each
Royer Expires October 2, 2005 [Page 13]
Internet-Draft iTIPbis April 2005
method is defined using a table that clarifies the property
constraints that define the particular method.
The following summarizes the methods that are defined for the
"VEVENT" calendar component.
+================+==================================================+
| Method | Description |
|================+==================================================|
| PUBLISH | Post notification of an event. Used primarily as |
| | a method of advertising the existence of an |
| | event. |
| | |
| REQUEST | Make a request for an event. This is an explicit |
| | invitation to one or more "Attendees". Event |
| | Requests are also used to update or change an |
| | existing event. |
| | |
| REPLY | Reply to an event request. Clients may set their |
| | status ("partstat") to ACCEPTED, DECLINED, |
| | TENTATIVE. |
| | |
| ADD | Add one or more instances to an existing event. |
| | |
| CANCEL | Cancel one or more instances of an existing |
| | event. |
| | |
| REFRESH | A request is sent to an "Organizer" by an |
| | "Attendee" asking for the latest version of an |
| | event to be resent to the requester. |
| | |
| COUNTER | Counter a REQUEST with an alternative proposal, |
| | Sent by an "Attendee" to the "Organizer". |
| | |
| DECLINECOUNTER | Decline a counter proposal. Sent to an |
| | "Attendee" by the "Organizer". |
+================+==================================================+
3.2.1 PUBLISH
The "PUBLISH" method in a "VEVENT" calendar component is an
unsolicited posting of an iCalendar object. Any CU may add published
components to their calendar. The "Organizer" MUST be present in a
published iCalendar component. "Attendees" MUST NOT be present. Its
expected usage is for encapsulating an arbitrary event as an
iCalendar object. The "Organizer" may subsequently update (with
another "PUBLISH" method), add instances to (with an "ADD" method),
Royer Expires October 2, 2005 [Page 14]
Internet-Draft iTIPbis April 2005
or cancel (with a "CANCEL" method) a previously published "VEVENT"
calendar component.
This method type is an iCalendar object that conforms to the
following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST equal "PUBLISH"
VEVENT 1+
DTSTAMP 1
DTSTART 1
ORGANIZER 1
SUMMARY 1 Can be null.
UID 1
RECURRENCE-ID 0 iCal-Basic does not support this.
SEQUENCE 1 MUST be present.
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of
values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be empty.
DTEND 0 or 1 if present DURATION MUST NOT be present
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0 Not needed in iCal-Basic
EXRULE 0 Not supported in iCal-Basic
GEO 0 Deprecated in iCal-Basic
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RELATED-TO 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0 Not supported in iCal-Basic
STATUS 0 or 1 MAY be one of TENTATIVE/CONFIRMED/CANCELLED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
ATTENDEE 0
REQUEST-STATUS 0
VALARM 0+
VFREEBUSY 0
VJOURNAL 0
Royer Expires October 2, 2005 [Page 15]
Internet-Draft iTIPbis April 2005
VTODO 0
VTIMEZONE 0 Not supported in iCal-Basic
X-COMPONENT 0+
3.2.2 REQUEST
The "REQUEST" method in a "VEVENT" component provides the following
scheduling functions:
. Invite "Attendees" to an event.
. Reschedule an existing event (increment SEQUENCE).
. Response to a REFRESH request (do not increment SEQUENCE, just
re-send).
. Update the details of an existing event, without rescheduling
it. (increment SEQUENCE)
. Update the status of "Attendees" of an existing event, without
rescheduling it. (increment SEQUENCE)
. Forward a "VEVENT" to another uninvited CU. (Do not increment
SEQUENCE).
. For an existing "VEVENT" calendar component, changing the role
of "Organizer" to another CU. (Increment SEQUENCE)
The "Organizer" originates the "REQUEST". The recipients of the
"REQUEST" method are the CUs invited to the event, the "Attendees".
"Attendees" use the "REPLY" method to convey attendance status to the
"Organizer".
The "UID" and "SEQUENCE" properties are used to distinguish the
various uses of the "REQUEST" method. If the "UID" property value in
the "REQUEST" is not found on the recipient's calendar, then the
"REQUEST" is for a new "VEVENT" calendar component. If the "UID"
property value is found on the recipient's calendar, then the
"REQUEST" is for a rescheduling, an update, or a reconfirm of the
"VEVENT" calendar component.
For the "REQUEST" method, multiple "VEVENT" components in a single
iCalendar object are only permitted when for components with the same
"UID" property. That is, a series of recurring events may have
instance-specific information. In this case, multiple "VEVENT"
components are needed to express the entire series. These would have
been received as method "ADD" components.
This method type is an iCalendar object that conforms to the
following property constraints:
Component/Property Presence
-----------------------------------------------------------------
METHOD 1 MUST be "REQUEST"
Royer Expires October 2, 2005 [Page 16]
Internet-Draft iTIPbis April 2005
VEVENT 1+
ATTENDEE 1+
DTSTAMP 1
DTSTART 1
ORGANIZER 1
SEQUENCE 1 MUST be present.
SUMMARY 1 Can be empty.
UID 1
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of values.
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be '1' and empty.
DTEND 0 or 1 if present DURATION MUST NOT be present.
DURATION 0 or 1 if present DTEND MUST NOT be present.
EXDATE 0 Not needed in iCal-Basic.
EXRULE 0 Not in iCal-Basic.
GEO 0 Deprecated in iCal-Basic.
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RECURRENCE-ID 0 Not in iCal-Basic.
RELATED-TO 0+
REQUEST-STATUS 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0 Not in iCal-Basic.
STATUS 0 or 1 MAY be one of TENTATIVE/CONFIRMED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
VALARM 0+
VTIMEZONE 0 Not in iCal-Basic.
X-COMPONENT 0+
VFREEBUSY 0
VJOURNAL 0
VTODO 0
3.2.2.1 Rescheduling an Event
The "REQUEST" method may be used to reschedule an event. A
rescheduled event involves a change to the existing event in terms of
Royer Expires October 2, 2005 [Page 17]
Internet-Draft iTIPbis April 2005
its time or recurrence intervals and possibly the location or
description. If the recipient CUA of a "REQUEST" method finds that
the "UID" property value already exists on the calendar, but that the
"SEQUENCE" (or "DTSTAMP") property value in the "REQUEST" method is
greater than the value for the existing event, then the "REQUEST"
method describes a rescheduling of the event. The old contents are
tossed an replaced by the new contents. The "Attendee" only needs to
reply if their "RSVP" parameter is set to true by the "Organizer".
The "Organizer" sends a method "REQUEST" component with additional
method "ADD" components only when needed for each appointment
rescheduled. All with the same "UID" property value. As the "ADD"
method can be used independently of the "REQUEST" method, each
additional "ADD" method sent in the replacement set MUST have the
"SEQUENCE" property value incremented. That is if the "REQUEST"
component has a "SEQUENCE" property value of '8', then the first
"ADD" method after that would have a "SEQUENCE" property value of
'9', the second "ADD" method would have a "SEQUENCE" property value
of '10', and so on until all of the instances that can not be
described by the proceeding components is sent. This the rules
consistent with receiving independent "ADD" method components at a
later time.
3.2.2.2 Updating or Reconfirmation of an Event
The "REQUEST" method may be used to update or reconfirm an event. An
update to an existing event does not involve changes to the time or
recurrence intervals, and might not involve a change to the location
or description for the event. If the recipient CUA of a "REQUEST"
method finds that the "UID" property value already exists on the
calendar and that the "SEQUENCE" property value in the "REQUEST" is
the same as the value for the existing event, then the "REQUEST"
method describes an update of the event details, but no rescheduling
of the event. And only if the newer object has a newer "DTSTAMP"
property value. Older objects are to be tossed.
The update "REQUEST" method is the appropriate response to a
"REFRESH" method sent from an "Attendee" to the "Organizer" of an
event.
The "Organizer" of an event may also send unsolicited "REQUEST"
methods. The unsolicited "REQUEST" methods may be used to update the
details of the event without rescheduling it, to update the
"partstat" parameter of "Attendees", or to reconfirm the event.
3.2.2.3 Delegating an Event to another CU
Not supported in iTIP-Basic.
Royer Expires October 2, 2005 [Page 18]
Internet-Draft iTIPbis April 2005
3.2.2.4 Changing the Organizer
The situation may arise where the "Organizer" of a VEVENT is no
longer able to perform the "Organizer" role and abdicates without
passing on the "Organizer" role to someone else. When this occurs
the "Attendees" of the VEVENT may use out-of-band mechanisms to
communicate the situation and agree upon a new "Organizer". The new
"Organizer" should then send out a new "REQUEST" with a modified
version of the VEVENT in which the "SEQUENCE" number has been
incremented and value of the "ORGANIZER" property has been changed to
the calendar address of the new "Organizer".
3.2.2.5 Sending on Behalf of the Organizer
Not supported in iTIP-Basic.
3.2.2.6 Forwarding to An Uninvited CU
An "Attendee" invited to an event may invite another uninvited CU to
the event. The invited "Attendee" accomplishes this by forwarding
the original "REQUEST" method to the uninvited CU. The "Organizer"
decides whether or not the uninvited CU is added to the attendee
list. If the "Organizer" decides not to add the uninvited CU no
further action is required, however the "Organizer" MUST send the
uninvited CU a "CANCEL" message. If the "Organizer" decides to add
an uninvited CU, a new "ATTENDEE" property is added for the uninvited
CU with its property parameters set as the "Organizer" deems
appropriate. When forwarding a "REQUEST" to another CU, the
forwarding "Attendee" MUST NOT make changes to the VEVENT property
set.
3.2.2.7 Updating Attendee Status
The "Organizer" of an event may also request updated status from one
or more "Attendees. The "Organizer" sends a "REQUEST" method to the
"Attendee" and sets the "ATTENDEE;RSVP=TRUE" property parameter. The
"SEQUENCE" property for the event is not changed from its previous
value. A recipient will determine that the only change in the
"REQUEST" is that their "RSVP" property parameter indicates a request
for updated status. The recipient MUST respond with a "REPLY" method
indicating their current status with respect to the "REQUEST".
3.2.3 REPLY
The "REPLY" method in a "VEVENT" calendar component is used to
respond (e.g., accept or decline) to a "REQUEST".
Royer Expires October 2, 2005 [Page 19]
Internet-Draft iTIPbis April 2005
The "REPLY" method may also be used to respond to an unsuccessful
"REQUEST" method. Depending on the value of the "REQUEST-STATUS"
property no scheduling action may have been performed.
The "Organizer" of an event may receive the "REPLY" method from a CU
not in the original "REQUEST". In addition, the "REPLY" method may
be received from an unknown CU (They were forwarded a copy). This
unknown "Attendee" may be accepted, or the "Organizer" may cancel the
event for the uninvited "Attendee" by sending a "CANCEL" method to
the uninvited "Attendee".
An "Attendee" can include a message to the "Organizer" using the
"COMMENT" property. For example, if the user indicates tentative
acceptance and wants to let the "Organizer" know why, the reason can
be expressed in the "COMMENT" property value.
The optional properties listed in the table below (those listed as
"0+" or "0 or 1") MUST NOT be changed from those of the original
request. If property changes are desired the COUNTER message must be
used.
This method type is an iCalendar object that conforms to the
following property constraints:
The "Attendee" only sends the specific information needed. If the
reply is for all instances in the "VEVENT" component, then the
"DTSTART", "DTEND", "RDATE", and "DURATION" properties MUST NOT be
included.
If the reply is for a subset of the instances, then the "DTSTART",
"DTEND", "RDATE", and "DURATION", proprties are used in exactly the
same way as a request. Multiple "REPLY" components MUST BE sent to
conver all instances in such a case. If the "Attendee" can attend
Monday, then two components are sent;, one saying YES to Monday, the
other NO to the other dates. The "Attendee" when replying must reply
to all instances in the "VEVENT" component.
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REPLY"
VEVENT 1+
ATTENDEE 1 MUST be the address of the Attendee
replying.
DTSTAMP 1
ORGANIZER 1
RECURRENCE-ID 0 Not supported in iCal-Basic.
UID 1 MUST be the UID of the original REQUEST
Royer Expires October 2, 2005 [Page 20]
Internet-Draft iTIPbis April 2005
SEQUENCE 1 MUST be the sequence number of the original
REQUEST.
ATTACH 0
CATEGORIES 0
CLASS 0
COMMENT 0 or 1
CONTACT 0+
CREATED 0
DESCRIPTION 0
DTEND 0 or 1 If present DURATION MUST NOT be present.
Only if DTSTART is supplied.
DTSTART 0 or 1 Only if this object is a reply for less
than all instances.
DURATION 0 or 1 If present DTEND MUST NOT be present. Only
if DTSTART is supplied.
EXDATE 0 Not in iCal-Basic
EXRULE 0 Not in iCal-Basic
GEO 0 Deprecated
LAST-MODIFIED 0 or 1
LOCATION 0
PRIORITY 0
RDATE 0+
RELATED-TO 0
RESOURCES 0
REQUEST-STATUS 0+
RRULE 0 Not in iCal-Basic
STATUS 0 or 1
SUMMARY 0
TRANSP 0
URL 0
X-PROPERTY 0+
VTIMEZONE 0 Not in iCal-Basic
X-COMPONENT 0+
VALARM 0
VFREEBUSY 0
VJOURNAL 0
VTODO 0
3.2.4 ADD
The "ADD" method in a "VEVENT" calendar component is used to add one
or more instances to an existing "VEVENT". Unlike the "REQUEST"
method, when using issuing an "ADD" method, the "Organizer" does not
send the full "VEVENT" description; only the new instance(s). The
Royer Expires October 2, 2005 [Page 21]
Internet-Draft iTIPbis April 2005
"ADD" method is especially useful if there are instance-specific
properties to be preserved in a recurring "VEVENT". For instance, an
"Organizer" may have originally scheduled a weekly Thursday meeting.
At some point, several instances changed. Location or start time may
have changed, or some instances may have unique "DESCRIPTION"
properties. The "ADD" method allows the "Organizer" to add new
instances to an existing event using a single ITIP-BASIC message when
it is not possible to define the recurring pattern in one "VEVENT"
component.
The "UID" must be that of the existing event. If the "UID" property
value in the "ADD" is not found on the recipient's calendar, then the
recipient MUST send a "REFRESH" to the "Organizer" in order to be
updated with the latest version of the "VEVENT". If an "Attendee"
implementation does not support the "ADD" method it should respond
with a "REQUEST-STATUS" value of 3.14 and ask for a "REFRESH".
This method type is an iCalendar object that conforms to the
following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "ADD"
VEVENT 1
DTSTAMP 1
DTSTART 1
ORGANIZER 1
SEQUENCE 1 MUST be greater than 0.
SUMMARY 1 Can be empty.
UID 1 MUST match that of the original event.
ATTACH 0+
ATTENDEE 0+
CATEGORIES 0 or 1 This property MAY contain a list of values.
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be empty.
DTEND 0 or 1 if present DURATION MUST NOT be present.
DURATION 0 or 1 if present DTEND MUST NOT be present.
EXDATE 0 Not in iCal-Basic.
EXRULE 0 Not in iCal-Basic.
GEO 0 Deprecated.
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
Royer Expires October 2, 2005 [Page 22]
Internet-Draft iTIPbis April 2005
RELATED-TO 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0 Not in iCal-Basic.
STATUS 0 or 1 MAY be one of TENTATIVE/CONFIRMED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
RECURRENCE-ID 0
REQUEST-STATUS 0
VALARM 0+
VTIMEZONE 0 Not in iCal-Basic
X-COMPONENT 0+
VFREEBUSY 0
VTODO 0
VJOURNAL 0
3.2.5 CANCEL
The "CANCEL" method in a "VEVENT" calendar component is used to send
a cancellation notice of an existing event request to the
"Attendees". The message is sent by the "Organizer" of the event.
For a recurring event, either the whole event or instances of an
event may be cancelled.
To cancel the complete appointment and all instances; the "UID"
property value for the event MUST be specified and the "DTSTART",
"DTEND", "DURATION", and "RDATE" properties must NOT be included.
The "SEQUENCE" property is incremented so the "Attendee"'s can tell
it is the newest revision of the appointment.
To cancel one or more instances of a "VEVENT", include the "DTSTART",
"DTEND", "DURATION", and "RDATE" properties exactly as would be sent
in a request. The "UID" property must match what the "Attendee" has.
If an "Attendee" gets a "CANCEL" method for a "UID" where the
"Attendee" does not have the "UID", then the "Attendee" needs to do a
"REFRESH" to get the latest copy of the component.
In all cases, the "SEQUENCE" property value in the "CANCEL" component
MUST BE larger than the "Attendee" has, or the "CANCEL" object is to
be ignored and the "Attendee" MUST do a "REFRESH" to get the latest
details of the appointment.
This method type is an iCalendar object that conforms to the
following property constraints:
Royer Expires October 2, 2005 [Page 23]
Internet-Draft iTIPbis April 2005
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "CANCEL"
VEVENT 1+
ATTENDEE 0+ MUST include all "Attendees" being removed
the event. MUST be sent to all "Attendees" if
the entire event is cancelled.
DTSTAMP 1
ORGANIZER 1
SEQUENCE 1
UID 1 MUST be the UID of the original REQUEST
COMMENT 0 or 1
ATTACH 0 Not needed in a CANCEL.
CATEGORIES 0 Not needed in a CANCEL.
CLASS 0 Not needed in a CANCEL.
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 Not needed in a CANCEL.
DTEND 0 or 1 If present DURATION MUST NOT be present
Only supplied if DTSTART is supplied.
DTSTART 0 or 1 Only supplied if less than all of
the instances are being cancled.
DURATION 0 or 1 if present DTEND MUST NOT be present
Only supplied if DTSTART is supplied.
EXDATE 0 Not in iCal-Basic.
EXRULE 0 Not in iCal-Basic.
GEO 0 Deprecated.
LAST-MODIFIED 0 or 1
LOCATION 0 Not needed in CANCEL.
PRIORITY 0 Not needed in CANCEL.
RDATE 0+ Only if less than all instances are
being cancled and only when DTSTART
is supplied..
RECURRENCE-ID 0 Not in iCal-Basic
RELATED-TO 0 Not needed in CANCEL.
RESOURCES 0 Not needed in CANCEL.
RRULE 0 Not in iCal-Basic
STATUS 0 Not needed in CANCEL.
SUMMARY 0 Not needed in CANCEL.
TRANSP 0 Not needed in CANCEL.
URL 0 Not needed in CANCEL.
X-PROPERTY 0+
REQUEST-STATUS 0
Royer Expires October 2, 2005 [Page 24]
Internet-Draft iTIPbis April 2005
VTIMEZONE 0 Not in iCal-Basic.
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 0
VALARM 0
3.2.6 REFRESH
The "REFRESH" method in a "VEVENT" calendar component is used by
"Attendees" of an existing event to request an updated description
from the event "Organizer". The "REFRESH" method must specify the
"UID" property of the event to update.
The "Organizer" replies with the latest copy of the appointment. A
"REQUEST" is sent with any additional "ADD" methods if needed.
This method type is an iCalendar object that conforms to the
following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REFRESH".
VEVENT 1
ATTENDEE 1 MUST be the address of requestor.
DTSTAMP 1
ORGANIZER 1
UID 1 MUST be the UID associated with original
REQUEST.
COMMENT 0 or 1
RECURRENCE-ID 0 Not in iCal-Basic.
X-PROPERTY 0+
ATTACH 0
CATEGORIES 0
CLASS 0
CONTACT 0
CREATED 0
DESCRIPTION 0
DTEND 0
DTSTART 0
DURATION 0
EXDATE 0
EXRULE 0
GEO 0
LAST-MODIFIED 0
Royer Expires October 2, 2005 [Page 25]
Internet-Draft iTIPbis April 2005
LOCATION 0
PRIORITY 0
RDATE 0
RELATED-TO 0
REQUEST-STATUS 0
RESOURCES 0
RRULE 0
SEQUENCE 0
STATUS 0
SUMMARY 0
TRANSP 0
URL 0
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 0
VTIMEZONE 0
VALARM 0
3.2.7 COUNTER
The "COUNTER" method for a "VEVENT" calendar component is used by an
"Attendee" of an existing event to submit to the "Organizer" a
counter proposal to the event description. The "Attendee" sends this
message to the "Organizer" of the event.
The counter proposal is an iCalendar object consisting of a VEVENT
calendar component describing the complete description of the
alternate event.
The "Organizer" rejects the counter proposal by sending the
"Attendee" a VEVENT "DECLINECOUNTER" method. The "Organizer" accepts
the counter proposal by rescheduling the event as described in
section 3.2.2.1 Rescheduling an Event.
This method type is an iCalendar object that conforms to the
following property constraints. The compoent is constructed just
like a "REQUEST" component with the entire proposal for the proposed
appointment, except the following:
Royer Expires October 2, 2005 [Page 26]
Internet-Draft iTIPbis April 2005
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "COUNTER"
VEVENT 1
ORGANIZER 1 MUST be the "Organizer" of the original
event.
SEQUENCE 1 MUST be present and must match the
appointment being countered.
UID 1 MUST be the UID associated with the REQUEST
being countered.
ATTENDEE 1 MUST BE the "Attendee" making the proposal.
All other properties and components are identical to the "VEVENT" "REQUEST".
3.2.8 DECLINECOUNTER
The "DECLINECOUNTER" method in a "VEVENT" calendar component is used
by the "Organizer" of an event to reject a counter proposal submitted
by an "Attendee". The "Organizer" must send the "DECLINECOUNTER"
message to the "Attendee" that sent the "COUNTER" method to the
"Organizer".
This method type is an iCalendar object that conforms to the
following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "DECLINECOUNTER"
VEVENT 1
DTSTAMP 1
ORGANIZER 1
UID 1 MUST, same UID specified in original
REQUEST and subsequent COUNTER
COMMENT 0 or 1
RECURRENCE-ID 0 Not in iCal-Basic
REQUEST-STATUS 0+
SEQUENCE 1 MUST match the value in the "Attendee"s
COUNTER component.
X-PROPERTY 0+
ATTACH 0
ATTENDEE 0
CATEGORIES 0
CLASS 0
CONTACT 0
CREATED 0
Royer Expires October 2, 2005 [Page 27]
Internet-Draft iTIPbis April 2005
DESCRIPTION 0
DTEND 0
DTSTART 0
DURATION 0
EXDATE 0
EXRULE 0
GEO 0
LAST-MODIFIED 0
LOCATION 0
PRIORITY 0
RDATE 0
RELATED-TO 0
RESOURCES 0
RRULE 0
STATUS 0
SUMMARY 0
TRANSP 0
URL 0
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 0
VTIMEZONE 0
VALARM 0
3.3 Methods For VFREEBUSY Components
This section defines the property set for the methods that are
applicable to the "VFREEBUSY" calendar component. Each of the
methods is defined using a restriction table.
This document only addresses the transfer of busy time information.
Applications desiring free time information MUST infer this from
available busy time information.
The busy time information within the iCalendar object MAY be grouped
into more than one "VFREEBUSY" calendar component. This capability
allows busy time periods to be grouped according to some common
periodicity, such as a calendar week, month, or year. In this case,
each "VFREEBUSY" calendar component MUST include the "ATTENDEE",
"DTSTART" and "DTEND" properties in order to specify the source of
the busy time information and the date and time interval over which
the busy time information covers.
The "FREEBUSY" property value MAY include a list of values, separated
by the COMMA character ([4] decimal 44). Alternately, multiple busy
Royer Expires October 2, 2005 [Page 28]
Internet-Draft iTIPbis April 2005
time periods MAY be specified with multiple instances of the
"FREEBUSY" property. Both forms MUST be supported by implementations
conforming to this document. Duplicate busy time periods SHOULD NOT
be specified in an iCalendar object. However, two different busy
time periods MAY overlap.
"FREEBUSY" properties should be sorted such that their values are in
ascending order, based on the start time, and then the end time, with
the earliest periods first. For example, today's busy time
information should appear after yesterday's busy time information.
And the busy time for this half-hour should appear after the busy
time for earlier today.
Since events may span a day boundary, free busy time period may also
span a day boundary. Individual "A" requests busy time from
individuals "B", "C" and "D". Individual "B" and "C" replies with
busy time data to individual "A". Individual "D" does not support
busy time requests and does not reply with any data. If the
transport binding supports exception messages, then individual "D"
returns an "unsupported capability" message to individual "A4.34.3".
The following summarizes the methods that are defined for the
"VFREEBUSY" calendar component.
|================|==================================================|
| Method | Description |
|================|==================================================|
| PUBLISH | Publish unsolicited busy time data. |
| REQUEST | Request busy time data. |
| REPLY | Reply to a busy time request. |
|================|==================================================|
3.3.1 PUBLISH
The "PUBLISH" method in a "VFREEBUSY" calendar component is used to
publish busy time data. The method may be sent from one CU to any
other. The purpose of the method is to provide a message for sending
unsolicited busy time data. That is, the busy time data is not being
sent as a "REPLY" to the receipt of a "REQUEST" method.
The "ATTENDEE" property must be specified in the busy time
information. The value is the CU address of the originator of the
busy time information.
This method type is an iCalendar object that conforms to the
following property constraints:
Royer Expires October 2, 2005 [Page 29]
Internet-Draft iTIPbis April 2005
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "PUBLISH"
VFREEBUSY 1+
DTSTAMP 1
DTSTART 1 DateTime values must be in UTC
DTEND 1 DateTime values must be in UTC
FREEBUSY 1+ MUST be BUSYTIME. Multiple instances are
allowed. Multiple instances must be sorted
in ascending order
ORGANIZER 1 MUST contain the address of originator of
busy time data.
COMMENT 0 or 1
CONTACT 0+
X-PROPERTY 0+
URL 0 or 1 Specifies busy time URL
ATTENDEE 0
DURATION 0
REQUEST-STATUS 0
UID 0
X-COMPONENT 0+
VEVENT 0
VTODO 0
VJOURNAL 0
VTIMEZONE 0
VALARM 0
3.3.2 REQUEST
The "REQUEST" method in a "VFREEBUSY" calendar component is used to
ask a "Calendar User" for their busy time information. The request
may be for a busy time information bounded by a specific date and
time interval.
This message only permits requests for busy time information. The
message is sent from a "Calendar User" requesting the busy time
information to one or more intended recipients.
If the originator of the "REQUEST" method is not authorized to make a
busy time request on the recipient's calendar system, then an
exception message SHOULD be returned in a "REPLY" method, but no busy
time data need be returned.
Royer Expires October 2, 2005 [Page 30]
Internet-Draft iTIPbis April 2005
This method type is an iCalendar object that conforms to the
following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REQUEST"
VFREEBUSY 1
ATTENDEE 1+ contain the address of the calendar store
DTEND 1 DateTime values must be in UTC
DTSTAMP 1
DTSTART 1 DateTime values must be in UTC
ORGANIZER 1 MUST be the request originator's address
UID 1
COMMENT 0 or 1
CONTACT 0+
X-PROPERTY 0+
FREEBUSY 0
DURATION 0
REQUEST-STATUS 0
URL 0
X-COMPONENT 0+
VALARM 0
VEVENT 0
VTODO 0
VJOURNAL 0
VTIMEZONE 0
3.3.3 REPLY
The "REPLY" method in a "VFREEBUSY" calendar component is used to
respond to a busy time request. The method is sent by the recipient
of a busy time request to the originator of the request.
The "REPLY" method may also be used to respond to an unsuccessful
"REQUEST" method. Depending on the "REQUEST-STATUS" value, no busy
time information may be returned.
This method type is an iCalendar object that conforms to the
following property constraints:
Royer Expires October 2, 2005 [Page 31]
Internet-Draft iTIPbis April 2005
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REPLY"
VFREEBUSY 1
ATTENDEE 1 (address of recipient replying)
DTSTAMP 1
DTEND 1 DateTime values must be in UTC
DTSTART 1 DateTime values must be in UTC
FREEBUSY 1+ (values MUST all be of the same data
type. Multiple instances are allowed.
Multiple instances MUST be sorted in
ascending order. Values MAY NOT overlap)
ORGANIZER 1 MUST be the request originator's address
UID 1
COMMENT 0 or 1
CONTACT 0+
REQUEST-STATUS 0+
URL 0 or 1 (specifies busy time URL)
X-PROPERTY 0+
DURATION 0
SEQUENCE 0
X-COMPONENT 0+
VALARM 0
VEVENT 0
VTODO 0
VJOURNAL 0
VTIMEZONE 0
3.4 Methods For VTODO Components
VTODO's are not in iCal-Basic.
3.5 Methods For VJOURNAL Components
VJOURNAL's are not in iCal-Basic.
3.6 Status Replies
The "REQUEST-STATUS" property may include the following values:
|==============+============================+=========================|
| Short Return | Longer Return Status | Offending Data |
| Status Code | Description | |
|==============+============================+=========================|
Royer Expires October 2, 2005 [Page 32]
Internet-Draft iTIPbis April 2005
| 2.0 | Success. | None. |
|==============+============================+=========================|
| 2.1 | Success but fallback taken | Property name and value |
| | on one or more property | MAY be specified. |
| | values. | |
|==============+============================+=========================|
| 2.2 | Success, invalid property | Property name MAY be |
| | ignored. | specified. |
|==============+============================+=========================|
| 2.3 | Success, invalid property | Property parameter name |
| | parameter ignored. | and value MAY be |
| | | specified. |
|==============+============================+=========================|
| 2.4 | Success, unknown non- | Non-standard property |
| | standard property ignored. | name MAY be specified. |
|==============+============================+=========================|
| 2.5 | Success, unknown non | Property and non- |
| | standard property value | standard value MAY be |
| | ignored. | specified. |
|==============+============================+=========================|
| 2.6 | Success, invalid calendar | Calendar component |
| | component ignored. | sentinel (e.g., BEGIN: |
| | | ALARM) MAY be |
| | | specified. |
|==============+============================+=========================|
| 2.7 | Success, request forwarded | Original and forwarded |
| | to Calendar User. | caluser addresses MAY |
| | | be specified. |
|==============+============================+=========================|
| 2.8 | Success, repeating event | RRULE or RDATE property |
| | ignored. Scheduled as a | name and value MAY be |
| | single component. | specified. |
|==============+============================+=========================|
| 2.9 | Success, truncated end date| DTEND property value |
| | time to date boundary. | MAY be specified. |
|==============+============================+=========================|
| 2.10 | Success, repeating VTODO | RRULE or RDATE property |
| | ignored. Scheduled as a | name and value MAY be |
| | single VTODO. | specified. |
|==============+============================+=========================|
| 2.11 | Success, unbounded RRULE | RRULE property name and |
| | clipped at some finite | value MAY be specified. |
| | number of instances | Number of instances MAY |
| | | also be specified. |
|==============+============================+=========================|
| 3.0 | Invalid property name. | Property name MAY be |
| | | specified. |
|==============+============================+=========================|
Royer Expires October 2, 2005 [Page 33]
Internet-Draft iTIPbis April 2005
| 3.1 | Invalid property value. | Property name and value |
| | | MAY be specified. |
|==============+============================+=========================|
| 3.2 | Invalid property parameter.| Property parameter name |
| | | and value MAY be |
| | | specified. |
|==============+============================+=========================|
| 3.3 | Invalid property parameter | Property parameter name |
| | value. | and value MAY be |
| | | specified. |
|==============+============================+=========================|
| 3.4 | Invalid calendar component | Calendar component |
| | sequence. | sentinel MAY be |
| | | specified (e.g., BEGIN: |
| | | VTIMEZONE). |
|==============+============================+=========================|
| 3.5 | Invalid date or time. | Date/time value(s) MAY |
| | | be specified. |
|==============+============================+=========================|
| 3.6 | Invalid rule. | Rule value MAY be |
| | | specified. |
|==============+============================+=========================|
| 3.7 | Invalid Calendar User. | Attendee property value |
| | |MAY be specified. |
|==============+============================+=========================|
| 3.8 | No authority. | METHOD and Attendee |
| | | property values MAY be |
| | | specified. |
|==============+============================+=========================|
| 3.9 | Unsupported version. | VERSION property name |
| | | and value MAY be |
| | | specified. |
|==============+============================+=========================|
| 3.10 | Request entity too large. | None. |
|==============+============================+=========================|
| 3.11 | Required component or | Component or property |
| | property missing. | name MAY be specified. |
|==============+============================+=========================|
| 3.12 | Unknown component or | Component or property |
| | property found | name MAY be specified |
|==============+============================+=========================|
| 3.13 | Unsupported component or | Component or property |
| | property found | name MAY be specified |
|==============+============================+=========================|
| 3.14 | Unsupported capability | Method or action MAY |
| | | be specified |
|==============+============================+=========================|
| 4.0 | Event conflict. Date/time | DTSTART and DTEND |
Royer Expires October 2, 2005 [Page 34]
Internet-Draft iTIPbis April 2005
| | is busy. | property name and values|
| | | MAY be specified. |
|==============+============================+=========================|
| 5.0 | Request MAY supported. | Method property value |
| | | MAY be specified. |
|==============+============================+=========================|
| 5.1 | Service unavailable. | ATTENDEE property value |
| | | MAY be specified. |
|==============+============================+=========================|
| 5.2 | Invalid calendar service. | ATTENDEE property value |
| | | MAY be specified. |
|==============+============================+=========================|
| 5.3 | No scheduling support for | ATTENDEE property value |
| | user. | MAY be specified. |
|==============+============================+=========================|
3.7 Implementation Considerations
3.7.1 Working With Recurrence Instances
Not supported in iCal-Basic.
3.7.2 Attendee Property Considerations
3.7.3 X-Tokens
Royer Expires October 2, 2005 [Page 35]
Internet-Draft iTIPbis April 2005
4. Examples
Examples are in a separate document.
Royer Expires October 2, 2005 [Page 36]
Internet-Draft iTIPbis April 2005
5. Application Protocol Fallbacks
5.1 Partial Implementation
iTIP applications that support this memo are required to support the
entire protocol.
5.1.1 Event-Related Fallbacks
This section will discuss how to interoperate with iTIP.
5.1.2 Latency Issues
With a store-and-forward transport, it is possible for events to
arrive out of sequence. That is, a "CANCEL" method may be received
prior to receiving the associated "REQUEST" for the calendar
component. This section discusses a few of these scenarios.
5.1.2.1 Cancellation of an Unknown Calendar Component.
The "Attendee" tosses the "CANCEL" component. If the "Attendee"
cares to see the appointment send a "REFRESH". If the "CANCEL" has
no "DTSTART" value, then all of the appointnemt has been canceled, no
point in doing a "REFRESH".
5.1.2.2 Unexpected Reply from an Unknown Delegate
Not supported in iCal-Basic.
5.1.3 Sequence Number
Under some conditions, a CUA may receive requests and replies with
the same "SEQUENCE" property value. The "DTSTAMP" property is
utilized as a tie-breaker when two items with the same "SEQUENCE"
property value are evaluated. The newest "DTSTAMP" value obsoletes
the older.
5.2 Security Considerations
ITIP-BASIC is an abstract transport protocol which will be bound to a
real-time transport, a store-and-forward transport, and perhaps other
transports. The transport protocol will be responsible for providing
facilities for authentication and encryption using standard Internet
mechanisms that are mutually understood between the sender and
receiver.
Royer Expires October 2, 2005 [Page 37]
Internet-Draft iTIPbis April 2005
5.2.1 Security Threats
5.2.1.1 Spoofing the "Organizer"
In iTIP-Basic, the "Organizer" (or someone working on the
"Organizer's" behalf) is the only person authorized to make changes
to an existing "VEVENT", "VTODO", "VJOURNAL" calendar component and
republish it or redistribute updates to the "Attendees". An
iCalendar object that maliciously changes or cancels an existing
"VEVENT", "VTODO" or "VJOURNAL" calendar component may be constructed
by someone other than the "Organizer" and republished or sent to the
"Attendees".
5.2.1.2 Spoofing the "Attendee"
In iTIP-Basic, an "Attendee" of a "VEVENT" or "VTODO" calendar
component (or someone working on the "Attendee's" behalf) is the only
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 may be constructed by
someone other than the real "Attendee" and sent to the "Organizer".
5.2.1.3 Unauthorized Replacement of the Organizer
There will be circumstances when "Attendees" of an event or to-do
decide, using out-of-band mechanisms, that the "Organizer" must be
replaced. When the new "Organizer" sends out the updated "VEVENT" or
"VTODO" the "Attendee's" CUA will detect that the "Organizer" has
been changed, but it has no way of knowing whether or not the change
was mutually agreed upon.
5.2.1.4 Eavesdropping
The iCalendar object is constructed with human-readable clear text.
Any information contained in an iCalendar object may be read and/or
changed by unauthorized persons while the object is in transit.
5.2.1.5 Flooding a Calendar
Implementations MAY provide a means to automatically incorporate
"REQUEST" methods into a calendar. This presents the opportunity for
a calendar to be flooded with requests, which effectively block all
the calendar's free time.
Royer Expires October 2, 2005 [Page 38]
Internet-Draft iTIPbis April 2005
5.2.1.6 Procedural Alarms
The "REQUEST" methods for "VEVENT" and "VTODO" calendar components
MAY contain "VALARM" calendar components. The "VALARM" calendar
component may be of type "PROCEDURE" and MAY have an attachment
containing an executable program. Implementations that incorporate
these types of alarms are subject to any virus or malicious attack
that may occur as a result of executing the attachment.
5.2.1.7 Unauthorized REFRESH Requests
It is possible for an "Organizer" to receive a "REFRESH" request from
someone who is not an "Attendee" of an event or to-do. Only
"Attendee's" of an event or to-do are authorized to receive replies
to "REFRESH" requests. Replying to such requests to anyone who is
not an "Attendee" may be a security problem.
5.2.2 Recommendations
For an application where the information is sensitive or critical and
the network is subject is subject to a high probability of attack,
iTIP-Basic transactions SHOULD be encrypted. This may be
accomplished using public key technology, specifically Security
Multiparts for MIME
[RFC-1847] in the iTIP-Basic transport binding. This helps mitigate
the threats of spoofing, eavesdropping and malicious changes in
transit.
5.2.2.1 Use of [RFC-1847] to secure iTIP-Basic transactions
iTIP-Basic transport bindings MUST provide a mechanism based on
Security Multiparts for MIME [RFC-1847] to enable authentication of
the sender's identity, and privacy and integrity of the data being
transmitted. This allows the receiver of a signed iCalendar object
to verify the identity of the sender. This sender may then be
correlated to an "ATTENDEE" property in the iCalendar object. If the
correlation is made and the sender is authorized to make the
requested change or update then the operation may proceed. It also
allows the message to be encrypted to prevent unauthorized reading of
the message contents in transit. iTIP-Basic transport binding
documents describe this process in detail.
Implementations MAY provide controls for users to disable this
capability.
Royer Expires October 2, 2005 [Page 39]
Internet-Draft iTIPbis April 2005
5.2.2.2 Implementation Controls
The threat of unauthorized replacement of the "Organizer" SHOULD be
mitigated by a calendar system that uses this protocol by providing
controls or alerts that make "Calendar Users" aware of such
"Organizer" changes and allowing them to decide whether or not the
request should be honored.
The threat of flooding a calendar SHOULD be mitigated by a calendar
system that uses this protocol by providing controls that may be used
to limit the acceptable sources for iTIP-Basic transactions, and
perhaps the size of messages and volume of traffic, by source.
The threat of malicious procedural alarms SHOULD be mitigated by a
calendar system that uses this protocol by providing controls that
may be used to disallow procedural alarms in iTIP-Basic transactions
and/or remove all alarms from the object before delivery to the
recipient.
The threat of unauthorized "REFRESH" requests SHOULD be mitigated by
a calendar system that uses this protocol by providing controls or
alerts that allow "Calendar User" to decide whether or not the
request should be honored. An implementation MAY decide to maintain,
for audit or historical purposes, "Calendar Users" who were part of
an attendee list and who were subsequently uninvited. Similar
controls or alerts should be provided when a "REFRESH" request is
received from these "Calendar Users" as well.
5.3 Acknowledgments
A hearty thanks to the following individuals who have participated in
the drafting, review and discussion of this memo:
tbd
6 References
[1] Royer, D., "Internet Calendaring and Scheduling Core Object
Specification - iCalendar Basic", draft-royer-ical-basic-02.txt,
November 2005.
[2] Royer, D., "Basic iCalendar Message-Based Interoperability
Protocol - iMIP Basic", draft-royer-imip-basic-00.txt, November
2005.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
Royer Expires October 2, 2005 [Page 40]
Internet-Draft iTIPbis April 2005
[4] "Coded Character Set--7-bit American Standard Code for
Information Interchange, ANSI X3.4", 1986.
Author's Address
Doug Royer
IntelliCal, LLC
267 Kentlands Blvd., #3041
Gaithersburg, MD 20878
USA
Phone: +1-866-594-8574
EMail: Doug@Royer.com
Royer Expires October 2, 2005 [Page 41]
Internet-Draft iTIPbis April 2005
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Royer Expires October 2, 2005 [Page 42]
