Calendaring Extensions to WebDAV (CalDAV)

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 [RFC2119].¶

The term "protected" is used in the Conformance field of property definitions as defined in Section 1.4.2 of [RFC3253].¶

When XML element types in the namespaces "DAV:" and "urn:ietf:params:xml:ns:caldav" are referenced in this document outside of the context of an XML fragment, the string "DAV:" and "CALDAV:" will be prefixed to the element type names respectively.¶

Definitions of XML elements in this document use XML element type declarations (as found in XML Document Type Declarations), described in Section 3.2 of [W3C.REC-xml-20040204].¶

The namespace "urn:ietf:params:xml:ns:caldav" is reserved for the XML elements defined in this specification, its revisions, and related CalDAV specifications. XML elements defined by individual implementations MUST NOT use the "urn:ietf:params:xml:ns:caldav" namespace, and instead should use a namespace that they control.¶

The XML declarations used in this document do not include namespace information. Thus, implementers MUST NOT use these declarations as the only way to create valid CalDAV properties or to validate CalDAV XML element type. Some of the declarations refer to XML elements defined by WebDAV [RFC2518] which use the "DAV:" namespace. Wherever such XML elements appear, they are explicitly prefixed with "DAV:" to avoid confusion.¶

Also note that some CalDAV XML element names are identical to WebDAV XML element names, though their namespace differs. Care must be taken not to confuse the two sets of names.¶

A "precondition" of a method describes the state of the server that must be true for that method to be performed. A "postcondition" of a method describes the state of the server that must be true after that method has been completed. If a method precondition or postcondition for a request is not satisfied, the response status of the request MUST be either 403 (Forbidden) if the request should not be repeated because it will always fail, or 409 (Conflict) if it is expected that the user might be able to resolve the conflict and resubmit the request.¶

In order to allow better client handling of 403 and 409 responses, a distinct XML element type is associated with each method precondition and postcondition of a request. When a particular precondition is not satisfied or a particular postcondition cannot be achieved, the appropriate XML element MUST be returned as the child of a top-level DAV:error element in the response body, unless otherwise negotiated by the request. In a 207 Multi-Status response, the DAV:error element would appear in the appropriate DAV:responsedescription element.¶

A CalDAV server is a calendaring-aware engine combined with a WebDAV repository. A WebDAV repository is a set of WebDAV collections, containing other WebDAV resources, within a unified URL namespace. For example, the repository "http://www.example.com/webdav/" may contain WebDAV collections and resources, all of which have URLs beginning with "http://www.example.com/webdav/". Note that the root URL "http://www.example.com/" may not itself be a WebDAV repository (for example, if the WebDAV support is implemented through a servlet or other Web server extension).¶

A WebDAV repository MAY include calendar data in some parts of its URL namespace, and non-calendaring data in other parts.¶

A WebDAV repository can advertise itself as a CalDAV server if it supports the functionality defined in this specification at any point within the root of the repository. That might mean that calendaring data is spread throughout the repository and mixed with non-calendar data in nearby collections (e.g., calendar data may be found in /home/lisa/calendars/ as well as in /home/bernard/calendars/, and non-calendar data in /home/lisa/contacts/). Or, it might mean that calendar data can be found only in certain sections of the repository (e.g., /calendar/). Calendaring features are only required in the repository sections that are or contain calendar object resources. So a repository confining calendar data to the /calendar/ collection would only need to support the CalDAV required features within that collection.¶

The CalDAV server or repository is the canonical location for calendar data and state information. Both CalDAV servers and clients MUST ensure that the data is consistent and compliant. Clients may submit requests to change data or download data. Clients may store calendar objects offline and attempt to synchronize at a later time. However, clients MUST be prepared for calendar data on the server to change between the time of last synchronization and when attempting an update, as calendar collections may be shared and accessible via multiple clients. Entity tags and other features make this possible.¶

Recurrence is an important part of the data model because it governs how many resources are expected to exist. This specification models a recurring calendar component and its recurrence exceptions as a single resource. In this model, recurrence rules, recurrence dates, exception rules, and exception dates are all part of the data in a single calendar object resource. This model avoids problems of limiting how many recurrence instances to store in the repository, how to keep recurrence instances in sync with the recurring calendar component, and how to link recurrence exceptions with the recurring calendar component. It also results in less data to synchronize between client and server, and makes it easier to make changes to all recurrence instances or to a recurrence rule. It makes it easier to create a recurring calendar component, and easier to delete all recurrence instances.¶

Clients are not forced to retrieve information about all recurrence instances of a recurring component. The CALDAV:calendar-query and CALDAV:calendar-multiget REPORTs defined in this document allow clients to retrieve only recurrence instances that overlap a given time range.¶

Calendar object resources contained in calendar collections MUST NOT contain more than one type of calendar component (e.g., VEVENT, VTODO, VJOURNAL, VFREEBUSY, etc.) with the exception of VTIMEZONE components which MUST be specified for each unique TZID parameter value specified in the iCalendar object. For instance, a calendar object resource can contain two VEVENT components and one VTIMEZONE component, but it cannot contain one VEVENT component and one VTODO component.¶

Calendar object resources contained in calendar collections MUST NOT specify the iCalendar METHOD property.¶

The UID property value of the calendar components contained in a calendar object resource MUST be unique in the scope of the calendar collection.¶

Calendar components in a calendar collection that have different UID property values MUST be stored in separate calendar object resources.¶

Calendar components with the same UID property value, in a given calendar collection, MUST be contained in the same calendar object resource. This ensures that all components in a recurrence "set" are contained in the same calendar object resource. In that case there will be one component without a RECURRENCE-ID property (the component that defines the recurrence pattern) and all the rest will have that property (these are the recurrence exceptions).¶

For example, given the following iCalendar object: ¶

 BEGIN:VCALENDAR
 PRODID:-//Example Corp.//CalDAV Client//EN
 VERSION:2.0
 BEGIN:VEVENT
 UID:1@example.com
 SUMMARY:One-off Meeting
 DTSTAMP:20041210T183904Z
 DTSTART:20041207T120000Z
 DTEND:20041207T130000Z
 END:VEVENT
 BEGIN:VEVENT
 UID:2@example.com
 SUMMARY:Weekly Meeting
 DTSTAMP:20041210T183838Z
 DTSTART:20041206T120000Z
 DTEND:20041206T130000Z
 RRULE:FREQ=WEEKLY
 END:VEVENT
 BEGIN:VEVENT
 UID:2@example.com
 SUMMARY:Weekly Meeting
 RECURRENCE-ID:20041213T120000Z
 DTSTAMP:20041210T183838Z
 DTSTART:20041213T130000Z
 DTEND:20041213T140000Z
 END:VEVENT
 END:VCALENDAR
        

The VEVENT component with the UID value "1@example.com", would be stored in its own calendar object resource. The two VEVENT components with the UID value "2@example.com", which represent a recurring event where one recurrence instance has been overridden, would be stored in the same calendar object resource.¶

A calendar collection contains calendar object resources that represent calendar components within a calendar. A calendar collection is manifested to clients as a WebDAV resource collection identified by a URL. A calendar collection MUST report the DAV:collection and CALDAV:calendar XML elements in the value of the DAV:resourcetype property. The element type declaration for CALDAV:calendar is: ¶

    <!ELEMENT calendar EMPTY>
        

A calendar collection can be created through provisioning (e.g., automatically created when a user's account is provisioned), or it can be created with the MKCALENDAR method (see Section 5.3.1). This method can be useful for a user to create a second calendar (e.g., soccer schedule) or for users to share a calendar (e.g., team events or conference room). Note however that this document doesn't define what extra calendar collections are for. Users must rely on non-standard cues to find out what a calendar collection is for, or use the CALDAV:calendar-description property defined in Section 5.2.1 to provide such a cue.¶

Calendar collections MUST only contain calendar object resources and collections that are not calendar collections. Furthermore, collections contained in calendar collections MUST NOT contain calendar collections. This specification does not define how collections contained in calendar collections are used and may relate to the calendar object resources contained in the calendar collections.¶

Multiple calendar collections MAY be children of the same collection.¶

A server supporting the features described in this document MUST include "calendar-access" as a field in the DAV response header from an OPTIONS request on any resource that supports any calendar properties, reports, method, or privilege. A value of "calendar-access" in the DAV response header MUST indicate that the server supports all MUST level requirements specified in this document.¶

This section defines properties that MAY be defined on calendar collections.¶

The creation of calendar collections and calendar object resources may be initiated by either a CalDAV client or by the CalDAV server. For example, a server might come preconfigured with a user's calendar collection, or the CalDAV client might request the server to create a new calendar collection for a given user. Servers might populate events as calendar objects inside a calendar collection, or clients might request the server to create events. Either way, both client and server MUST comply with the requirements in this document, and MUST understand objects appearing in calendar collections or according to the data model defined here.¶

CalDAV servers MUST support and adhere to the requirements of WebDAV ACL [RFC3744]. WebDAV ACL provides a framework for an extensible set of privileges that can be applied to WebDAV collections and ordinary resources. CalDAV servers MUST also support the calendaring privilege defined in this section.¶

This section defines an additional property for WebDAV principal resources as defined in [RFC3744].¶

The REPORT method (defined in Section 3.6 of [RFC3253]) provides an extensible mechanism for obtaining information about one or more resources. Unlike the PROPFIND method, which returns the value of one or more named properties, the REPORT method can involve more complex processing. REPORT is valuable in cases where the server has access to all of the information needed to perform the complex request (such as a query), and where it would require multiple requests for the client to retrieve the information needed to perform the same request.¶

CalDAV servers MUST support the DAV:expand-property REPORT defined in Section 3.8 of [RFC3253].¶

Servers MAY support the REPORTs defined in this document on ordinary collections, that is, collections that are not calendar collections. In computing responses to the REPORTs defined in this document, servers MUST only consider calendar object resources contained in calendar collections, subject also to the value of the Depth request header.¶

iCalendar provides a way to specify DATE and DATE-TIME values that are not bound to any time zone in particular, hereafter called "floating date" and "floating time" respectively. These values are used to represent the same day, hour, minute and second value regardless of which time zone is being observed. For instance, the DATE value "20051111", represents November 11th, 2005 in no specific time zone, while the DATE-TIME value "20051111T111100" represents November 11th, 2005 at 11:11 AM in no specific time zone.¶

CalDAV servers may need to convert "floating date" and "floating time" values in date with UTC time values in the processing of calendaring REPORT requests.¶

For the CALDAV:calendar-query REPORT, CalDAV servers MUST rely on the value of the CALDAV:timezone XML element, if specified as part of the request body, to perform the proper conversion of "floating date" and "floating time" values to date with UTC time values. If the CALDAV:timezone XML element is not specified in the request body, CalDAV servers MUST rely on the value of the CALDAV:calendar-timezone property, if defined, else the CalDAV servers MAY rely on the time zone of their choice.¶

For the CALDAV:free-busy-query REPORT, CalDAV servers MUST rely on the value of the CALDAV:calendar-timezone property, if defined, to compute the proper FREEBUSY time period value as date with UTC time, for calendar components scheduled with "floating date" or "floating time". If the CALDAV:calendar-timezone property is not defined, CalDAV servers MAY rely on the time zone of their choice.¶

Some of the reports defined in this section can be targeted at calendar object resources within a specific time range. To determine whether a calendar object resource matches the time range filter element, the start and end times for the particular type of object are determined and then compared to the requested time range. If the start and end overlap the requested time range, then the calendar object resource matches the filter element. The rules defined in [RFC2445] for determining the actual start and end times of calendar components MUST be used, along with the rules for determining overlap specified in Section 9.8 of this document.¶

When such time range filtering is used, special consideration must be given to recurring calendar components such as VEVENT and VTODO components. The server MUST expand recurring components to determine whether any recurrence instances overlap the specified time range. If one or more recurrence instances overlap the time range, then the calendar object resource matches the filter element.¶

In addition, CalDAV provides three ways to determine which components of a calendar object resource are returned from the recurrence set. The three options are: ¶

1. Return all the calendar components contained in the calendar object resources. This includes the component that defines the recurrence set, referred to as the "master component", as well as the components that define exceptions to the recurrence set, referred to as the "overridden components". According to the rules defined in Section 3.2 all recurrence instances of a recurring component will always be contained in the same calendar object resource.
2. Return the "master component" and only the "overridden components" that currently or originally overlap the specified time range. This avoids the need for clients to process "overridden components" outside of the time range they are interested in. See Section 9.5.6.
3. Return "expanded" calendar components that represent only those recurrence instances in the recurrence set that overlap the specified time range. This avoids the need for clients to do any recurrence processing themselves as the server does the expansion for them and provides the list of instances. See Section 9.5.5.

The CALDAV:calendar-query REPORT performs a search for all calendar object resources that match a specified filter. The response of this REPORT will contain all the WebDAV properties and calendar object resource data specified in the request. In the case of the CALDAV:calendar-data XML element, one can explicitly specify the calendar components and properties that should be returned in the calendar object resource data that matches the filter.¶

The format of this REPORT is modeled on the PROPFIND method. The request and response bodies of the CALDAV:calendar-query REPORT use XML elements that are also used by PROPFIND. In particular the request can include XML elements to request WebDAV properties to be returned. When that occurs the response should follow the same behavior as PROPFIND with respect to the DAV:multistatus response elements used to return specific property results. For instance, a request to retrieve the value of a property which does not exist is an error and MUST be noted with a response XML element which contains a 404 (Not Found) status value.¶

Support for the CALDAV:calendar-query REPORT is REQUIRED.¶

Marshalling: ¶

• The request body MUST be a CALDAV:calendar-query XML element as defined in Section 9.4.
• The response body for a successful request MUST be a DAV:multistatus XML element (i.e., the response uses the same format as the response for PROPFIND). In the case where there are no response elements, the returned DAV:multistatus XML element is empty.
• The response body for a successful CALDAV:calendar-query REPORT request MUST contain a DAV:response element for each iCalendar object that matched the search filter. Calendar data is being returned in the CALDAV:calendar-data XML element inside the DAV:propstat XML element.

Preconditions: ¶

• (CALDAV:supported-calendar-data): The attributes "content-type" and "version" of the CALDAV:calendar-data XML elements specify a media type supported by the server for calendar object resources.
• (CALDAV:valid-filter): The CALDAV:filter XML element specified in the REPORT request MUST be valid. For instance, a CALDAV:filter cannot nest a <C:comp name="VEVENT"> element in a <C:comp name="VTODO"> element, or a CALDAV:filter cannot nest a <C:time-range start="..." end="..."> element in a <C:prop name="SUMMARY"> element.

Postconditions: ¶

• (DAV:number-of-matches-within-limits): The number of matching calendar object resources must fall within server-specific, predefined limits. For example, this condition might be triggered if a search specification would cause the return of an extremely large number of responses.

The CALDAV:calendar-multiget REPORT is used to retrieve specific calendar object resources from within a collection, if the Request-URI is a collection, or to retrieve a specific calendar object resource, if the Request-URI is a calendar object resource. This REPORT is similar to the CALDAV:calendar-query REPORT (see Section 7.6), except that it takes a list of DAV:href elements instead of a CALDAV:filter element to determine which calendar object resources to return.¶

Support for the calendar-multiget REPORT is REQUIRED.¶

Marshalling: ¶

• The request body MUST be a CALDAV:calendar-multiget XML element (see Section 9.9). If the Request-URI is a collection resource, then the DAV:href elements MUST refer to resources within that collection, and they MAY refer to resources at any depth within the collection. As a result the "Depth" header MUST be ignored by the server and SHOULD NOT be sent by the client. If the Request-URI refers to a non-collection resource, then there MUST be a single DAV:href element that is equivalent to the Request-URI.
• The response body for a successful request MUST be a DAV:multistatus XML element. In the case where there are no response elements, the returned DAV:multistatus XML element is empty.
• The response body for a successful CALDAV:calendar-multiget REPORT request MUST contain a DAV:response element for each calendar object resource referenced by the provided set of DAV:href elements. Calendar data is being returned in the CALDAV:calendar-data element inside the DAV:prop element.
• In the case of an error accessing any of the provided DAV:href resources, the server MUST return the appropriate error status code in the DAV:status element of the corresponding DAV:response element.

Preconditions: ¶

• (CALDAV:supported-calendar-data): The attributes "content-type" and "version" of the CALDAV:calendar-data XML elements specify a media type supported by the server for calendar object resources.

Postconditions: ¶

• None.

The CALDAV:free-busy-query REPORT generates a VFREEBUSY component containing free busy information for all the calendar object resources targeted by the request and which have the CALDAV:read-free-busy or DAV:read privilege granted to the current user.¶

Only VEVENT components without a TRANSP property or with the TRANSP property set to "OPAQUE", and VFREEBUSY components SHOULD be considered to generate the free busy time information.¶

In the case of VEVENT components, the free or busy time type (FBTYPE) of the FREEBUSY properties in the returned VFREEBUSY component SHOULD be derived from the value of the TRANSP and STATUS properties as outlined in the table below: ¶

      +---------------------------++------------------+
      |          VEVENT           ||    VFREEBUSY     |
      +-------------+-------------++------------------+
      | TRANSP      | STATUS      || FBTYPE           |
      +=============+=============++==================+
      |             | CONFIRMED   || BUSY             |
      |             | (default)   ||                  |
      | OPAQUE      +-------------++------------------+
      | (default)   | CANCELLED   || FREE             |
      |             +-------------++------------------+
      |             | TENTATIVE   || BUSY-TENTATIVE   |
      |             +-------------++------------------+
      |             | x-name      || BUSY or          |
      |             |             || x-name           |
      +-------------+-------------++------------------+ 
      |             | CONFIRMED   ||                  |
      | TRANSPARENT | CANCELLED   || FREE             |
      |             | TENTATIVE   ||                  |
      |             | x-name      ||                  |
      +-------------+-------------++------------------+
        

Duplicate busy time periods with the same FBTYPE parameter value SHOULD NOT be specified in the returned VFREEBUSY component. Servers SHOULD coalesce consecutive or overlapping busy time period of the same type. Busy time periods with different FBTYPE parameter values MAY overlap.¶

Support for the CALDAV:free-busy-query REPORT is REQUIRED.¶

Marshalling: ¶

• The request body MUST be a CALDAV:free-busy-query XML element (see Section 9.10, which MUST contain exactly one CALDAV:time-range XML element, as defined in Section 9.8.
• The request MAY include a Depth header. If no Depth header is included, Depth:0 is assumed.
• The response body for a successful request MUST be an iCalendar object that contains exactly one VFREEBUSY component that describes the busy time intervals for the calendar object resources containing VEVENT or VFREEBUSY components that satisfy the Depth value and for which the current user is at least granted the CALDAV:read-free-busy privilege. If no calendar object resource are found to satisfy these conditions a VFREEBUSY component with no FREEBUSY property MUST be returned. This REPORT only returns busy time information. Free time information can be inferred from the returned busy time information.
• If the current user is not granted the DAV:read privilege on the Request-URI, the CALDAV:free-busy-query REPORT request MUST fail and return a 404 (Not Found) status value. This restriction will prevent users from discovering URLs of resources for which they are only granted the CALDAV:read-free-busy privilege.

Preconditions: ¶

• None.

Postconditions: ¶

• (DAV:number-of-matches-within-limits): The number of matching calendar object resources must fall within server-specific, predefined limits. For example, this postcondition might fail if the specified CALDAV:time-range would cause an extremely large number calendar object resources to be considered to compute the response.

There are a number of actions clients can take which will be legal (the server will not return errors) but which can degrade interoperability with other client implementations accessing the same data. For example, a recurrence rule could be replaced with a set of recurrence dates, a single recurring event could be replaced with a set of independent resources to represent each recurrence, or the start/end time values can be translated from the original timezone to another timezone. Although this advice amounts to iCalendar interoperability best practices and is not limited only to CalDAV usage, interoperability problems are likely to be more evident in CalDAV use cases.¶

WebDAV already provides functionality required to synchronize a collection or set of collections, make changes offline, and a simple way to resolve conflicts when reconnected. ETags are the key to making this work, but these are not required of all WebDAV servers. Since offline functionality is more important to calendar applications than to some other WebDAV applications, CalDAV servers MUST support ETags as specified in Section 5.3.3.¶

WebDAV locks can be used to prevent two clients modifying the same resource from either overwriting each others' changes (though that problem can also be solved by using ETags) or wasting time making changes that will conflict with another set of changes. In a multi-user calendar system, an interactive calendar client could lock an event while the user is editing the event, and unlock the event when the user finishes or cancels. Locks can also be used to prevent changes while data is being reorganized. For example, a calendar client might lock two calendar collections prior to moving a bunch of calendar resources from one to another.¶

Clients are responsible for requesting a lock timeout period that is appropriate to the use case. When the user explicitly decides to reserve a resource and prevent other changes, a long timeout might be appropriate, but in cases when the client automatically decides to lock the resource the timeout should be short (and the client can always refresh the lock should it need to). A short lock timeout means that if the client is unable to remove the lock, the other calendar users aren't prevented from making changes.¶

Much of the time a calendar client (or agent) will discover a new calendar's location by being provided directly with the URL. E.g. a user will type his or her own calendar location into client configuration information, or copy and paste a URL from email into the calendar application. The client need only confirm that the URL points to a resource which is a calendar collection. The client may also be able to browse WebDAV collections to find calendar collections.¶

The choice of HTTP URLs means that calendar object resources are backward compatible with existing software, but does have the disadvantage that existing software does not usually know to look at the OPTIONS response to that URL to determine what can be done with it. This is somewhat of a barrier for WebDAV usage as well as with CalDAV usage. This specification does not offer a way through this other than making the information available in the OPTIONS response should this be requested.¶

For calendar sharing and scheduling use cases, one might wish to find the calendar belonging to another user. If the other user has a calendar in the same repository, that calendar can be found by using the principal namespace required by WebDAV ACL support. For other cases, the authors have no universal solution but implementors can consider whether to use vCard [RFC2426] or LDAP [RFC2251] standards together with calendar attributes [RFC2739].¶

Because CalDAV requires servers to support WebDAV ACL [RFC3744] including principal namespaces, and with the addition of the CALDAV:calendar-home-set property, there are a couple options for CalDAV clients to find one's own calendar or another user's calendar.¶

The server performs a case-sensitive or caseless search for a matching string subset of "Laurie" within the DAV:displayname property. Thus, the server might return "Laurie Dusseault", "Laurier Desruisseaux" or "Wilfrid Laurier" all as matching DAV:displayname values, and the calendars for each of these.¶

CalDAV clients MAY create attachments in calendar components either as inline or external. This section contains some guidelines on creating and managing attachments.¶

Note that all CalDAV calendar collections (including those which the user might treat as public or group calendars) can contain alarm information on events and to-dos. Users can synchronize a calendar between multiple devices and decide to have alarms execute on a different device than the device that created the alarm. Not all alarm action types are completely interoperable (e.g., those which name a sound file to play).¶

• When the action is "AUDIO", and the client is configured to execute the alarm, the client SHOULD play the suggested sound if it's available or play another sound, but SHOULD NOT rewrite the alarm just to replace the suggested sound with a sound that's locally available.
• When the action is "DISPLAY", and the client is configured to execute the alarm, the client SHOULD execute a display alarm by displaying either according to the suggested description or some reasonable replacement, but SHOULD NOT rewrite the alarm for its own convenience.
• When the action is "EMAIL", and the client is incapable of sending email, it SHOULD ignore the alarm but MUST continue to synchronize the alarm itself.
• This specification makes no recommendations about executing alarm of type PROCEDURE except to note that clients are advised to take care to avoid creating security holes by executing these.

Non-interoperable alarm information (e.g., should somebody define a color to be used in a display alarm) should be put in non-standard properties inside the VALARM component in order to keep the basic alarm usable on all devices.¶

Clients that allow changes to calendar object resources MUST synchronize the alarm data that already exists in the resources. Clients MAY execute alarms that are downloaded in this fashion, possibly based on user preference. If a client is only doing read operations on a calendar and there is no risk of losing alarm information, then the client MAY discard alarm information.¶

This specification makes no attempt to provide multi-user alarms on group calendars or to find out who an alarm is intended for. Addressing those issues might require extensions to iCalendar, for example to store alarms per-user or indicate which user a VALARM was intended for. In the meantime, clients might maximize interoperability by generally not uploading alarm information to public, group or resource calendars.¶

Name:

calendar

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Specifies the resource type of a calendar collection.

Description:

See Section 4.2.

Definition:

      <!ELEMENT calendar EMPTY>
              

Name:

mkcalendar

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Specifies a request that lists the WebDAV property values to be set for a calendar collection resource.

Description:

See Section 5.3.1.

Definition:

      <!ELEMENT mkcalendar (DAV:set)>
              

Name:

mkcalendar-response

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Specifies a response body for a successful MKCALENDAR request.

Description:

See Section 5.3.1.

Definition:

      <!ELEMENT mkcalendar-response ANY>
              

Name:

calendar-query

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Defines a REPORT for querying calendar object resources.

Description:

See Section 7.6.

Definition:

      <!ELEMENT calendar-query ((DAV:allprop |
                                 DAV:propname |
                                 DAV:prop)?, filter, timezone?)>
              

Name:

calendar-data

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Used to (1) specify a supported media type for calendar object resources when nested in the CALDAV:supported-calendar-data property; (2) specify which parts of a calendar object resource should be returned by a given calendaring REPORT; and (3) specify the content of a calendar object resource in a response to a calendaring REPORT.

Description:

When nested in the CALDAV:supported-calendar-data property, the CALDAV:calendar-data XML element specifies a media type supported by the CalDAV server for calendar object resources.

When used in a calendaring REPORT request, the CALDAV:calendar-data XML element specifies which parts of calendar object resources need to be returned in the response. If the CALDAV:calendar-data XML element doesn't contain any CALDAV:comp element, calendar object resources will be returned in their entirety.

Finally, when used in a calendaring REPORT response, the CALDAV:calendar-data XML element specifies the content of a calendar object resource. Given that XML parsers normalizes the two-character sequence CRLF (US-ASCII decimal 13 and US-ASCII decimal 10) to a single LF character (US-ASCII decimal 10), the CR character (US-ASCII decimal 13) MAY be omitted in calendar object resources specified in the CALDAV:calendar-data XML element. Furthermore, calendar object resources specified in the CALDAV:calendar-data XML element MAY be invalid per their media type specification if the CALDAV:calendar-data XML element part of the calendaring REPORT request did not specify required properties (e.g., UID, DTSTAMP, etc.) or specified a CALDAV:prop XML element with the "novalue" attribute set to "yes".

Note:

The CALDAV:calendar-data XML element is specified in requests and responses inside the DAV:prop XML element as if it were a WebDAV property. However, the CALDAV:calendar-data XML element is not a WebDAV property and as such it is not returned in PROPFIND responses nor used in PROPPATCH requests.

Definition:

      <!ELEMENT calendar-data ((comp?, (expand |
                                        limit-recurrence-set)?,
                                        limit-freebusy-set?) |
                               #PCDATA)?> 
      PCDATA value: iCalendar object

      <!ATTLIST calendar-data content-type CDATA "text/calendar">
                              version CDATA "2.0">
      content-type value: a MIME media type
      version value: a version string
              

Name:

filter

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Specifies a filter to limit the set of calendar components returned by the server.

Description:

The CALDAV:filter XML element specifies the search filter used to limit the calendar components returned by a calendaring REPORT request.

Definition:

      <!ELEMENT filter (comp-filter)>
             

Name:

timezone

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Specifies the time zone component...

Description:

The CALDAV:timezone XML element specifies that for a given calendaring REPORT request the server MUST rely on the specified VTIMEZONE component instead of the CALDAV:calendar-timezone property of the calendar collection in which the calendar object resource is contained to resolve "date" values and "date with local time" values (i.e., floating time) to "date with UTC time" values. The server will require this information to determine if a calendar component scheduled with "date" values or "date with local time" values intersect a CALDAV:time-range specified in a CALDAV:calendar-query REPORT.

Definition:

      <!ELEMENT timezone (#PCDATA)>
      PCDATA value: an iCalendar object with exactly one VTIMEZONE
              

Name:

time-range

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

Specifies a time range to limit the set of calendar components returned by the server.

Description:

The CALDAV:time-range XML element specifies that for a given calendaring REPORT request the server MUST only return the calendar object resources that, depending on the context, have a component or property or parameter whose value intersect a specified time range. The "start" attribute specifies the inclusive start of the time range, and the "end" attribute specifies the non-inclusive end of the time range. Both attributes are specified as "date with UTC time" value. While the "start" and "end" attributes are not required to allow time ranges opened at one end, at least one of them MUST be specified in the CALDAV:time-range element.

A VEVENT component overlaps a given time range if:

      (DTSTART <= start AND DTEND > start) OR
      (DTSTART <= start AND DTSTART+DURATION > start) OR
      (DTSTART >= start AND DTSTART < end) OR
      (DTEND   > start AND DTEND <= end)
              

A VEVENT component with no DTSTART and DTEND properties does not overlap any time range.

A VTODO component overlaps a given time range if:

      (DTSTART <= start AND DUE >= start) OR
      (DTSTART <= start AND DTSTART+DURATION > start) OR
      (DTSTART >= start AND DTSTART < end) OR
      (DUE     >= start AND DUE < end)
              

A VTODO component with no DTSTART and DUE properties does not overlap any time range.

A VJOURNAL component overlaps a given time range if:

      DTSTART >= start AND DTSTART < end
              

A VJOURNAL component with no DTSTART property does not overlap any time range.

A VFREEBUSY component overlaps a given time range if for any of its FREEBUSY property value the following condition holds:

      freebusy-period-start >= start AND freebusy-period-end < end
              

A VFREEBUSY component with no FREEBUSY property does not overlap any time range.

A VALARM component overlaps a given time range if:

      trigger-time >= start AND trigger-time < end
              

A VALARM component can be defined such that it triggers repeatedly. Such a VALARM component is said to overlap a given time range if at least one of its trigger overlap the time range.

The calendar properties COMPLETED, CREATED, DTSTAMP and LAST-MODIFIED overlaps a given time range

      date-time >= start AND date-time < end
              

The semantic of CALDAV:time-range is not defined for any other calendar properties.

Definition:

      <!ELEMENT time-range EMPTY>

      <!ATTLIST time-range start CDATA #IMPLIED
                          end   CDATA #IMPLIED>
      start value: an iCalendar "date with UTC time"
      end value: an iCalendar "date with UTC time"
              

Name:

calendar-multiget

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

CalDAV REPORT used to retrieve specific calendar object resources.

Description:

See Section 7.7.

Definition:

      <!ELEMENT calendar-multiget ((DAV:allprop |
                                   DAV:propname |
                                   DAV:prop)?, DAV:href+)>
              

Name:

free-busy-query

Namespace:

urn:ietf:params:xml:ns:caldav

Purpose:

CalDAV REPORT used to generate a VFREEBUSY to determine busy time over a specific time range.

Description:

See Section 7.8.

Definition:

      <!ELEMENT free-busy-query (time-range)>
              

URI: urn:ietf:params:xml:ns:caldav¶

Registrant Contact: See the "Author's Address" section of this document.¶

XML: None. Namespace URIs do not represent an XML specification.¶

14.1. Normative References

[RFC2119]

Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels”, BCP 14, RFC 2119, March 1997.

[RFC2246]

Dierks, T. and C. Allen, “The TLS Protocol Version 1.0”, RFC 2246, January 1999.

[RFC2445]

Dawson, F., Stenerson, D., “Internet Calendaring and Scheduling Core Object Specification (iCalendar)”, RFC 2445, November 1998.

[RFC2446]

Silverberg, S., Mansour, S., Dawson, F., and R. Hopson, “iCalendar Transport-Independent Interoperability Protocol (iTIP) Scheduling Events, BusyTime, To-dos and Journal Entries”, RFC 2446, November 1998.

[RFC2518]

Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D. Jensen, “HTTP Extensions for Distributed Authoring -- WEBDAV”, RFC 2518, February 1999.

[RFC2616]

Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1”, RFC 2616, June 1999.

[RFC2818]

Rescorla, E., “HTTP Over TLS”, RFC 2818, May 2000.

[RFC3253]

Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. Whitehead, “Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)”, RFC 3253, March 2002.

[RFC3688]

Mealling, M., “The IETF XML Registry”, BCP 81, RFC 3688, January 2004.

[RFC3744]

Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, “Web Distributed Authoring and Versioning (WebDAV) Access Control Protocol”, RFC 3744, May 2004.

[UNICODE4]

The Unicode Consortium, “The Unicode Standard, Version 4.0”, Addison-Wesley, Boston, MA. ISBN 0-321-18578-1, August 2003, <http://www.unicode.org/versions/Unicode4.0.0/>.

[W3C.REC-xml-20040204]

Maler, E., Paoli, J., Yergeau, F., Bray, T., and C. Sperberg-McQueen, “Extensible Markup Language (XML) 1.0 (Third Edition)”, World Wide Web Consortium FirstEdition REC-xml-20040204, February 2004, <http://www.w3.org/TR/2004/REC-xml-20040204>.

14.2. Informative References

[I-D.ietf-webdav-quota]

Korver, B. and L. Dusseault, “Quota and Size Properties for DAV Collections”, Internet-Draft draft-ietf-webdav-quota-07 (work in progress), April 2005.

[RFC2251]

Wahl, M., Howes, T., and S. Kille, “Lightweight Directory Access Protocol (v3)”, RFC 2251, December 1997.

[RFC2426]

Dawson, F. and T. Howes, “vCard MIME Directory Profile”, RFC 2426, September 1998.

[RFC2739]

Small, T., Hennessy, D., and F. Dawson, “Calendar Attributes for vCard and LDAP”, RFC 2739, January 2000.

1. Numerous editorial changes.
2. Removed the CALDAV:is-defined XML element.
3. Removed section on privilege aggregation.
4. Renamed the CALDAV:expand-recurrence-set XML element to CALDAV:expand and clarified the server behavior.
5. Renamed the CALDAV:calendar-component-restriction-set XML element to CALDAV:supported-calendar-component-set.
6. Renamed the CALDAV:calendar-restrictions XML element to CALDAV:supported-calendar-data.
7. Renamed some preconditions as "success conditions" instead of "failure causes". For instance, the precondition CALDAV:calendar-collection-location-bad has been renamed to CALDAV:calendar-collection-location-ok.
8. Reordered some sections.
9. Clarified the definition of CALDAV:time-range to specify that a repeating VALARM component is said to intersect a given time range if at least one of its trigger intersect the time range.
10. Clarified that calendar object resources stored in calendar collections MUST NOT specify the iCalendar METHOD property.
11. Clarified that CALDAV:calendar-data XML element is not a WebDAV property even though it is specified in the DAV:prop XML element in both calendaring REPORT requests and responses.
12. Clarified CALDAV:limit-recurrence-set with respect to the RANGE parameter on the RECURRENCE-ID property.
13. Changed the CALDAV:free-busy-query XML element to contain exactly one CALDAV:time-range XML element.
14. Changed many ELEMENT and ATTLIST declarations to comply with DTD syntax.
15. Changed XML element CALDAV:calendar-query to allow new XML element CALDAV:timezone.
16. Changed the XML elements CALDAV:time-range, CALDAV:expand and CALDAV:limit-recurrence-set to only allow DATE-TIME with UTC time values for the "start" and "end" attributes.
17. Changed description of CALDAV:limit-recurrence-set to specify that re-scheduled "overridden" recurrence instances whose original scheduled time used to overlap the time range specified by the "start" and "end" attribute should always be returned in a REPORT response.
18. Changed the description of the value of CALDAV:calendar-data XML element to specify that the CR character (US-ASCII decimal 13) MAY be omitted in the iCalendar object specified in this XML element.
19. Added specific requirements for entity tags support.
20. Added more preconditions.
21. Added further guidelines about finding calendars.
22. Added XML element CALDAV:limit-freebusy-set to limit the set of FREEBUSY property values returned in VFREEBUSY components.
23. Added property CALDAV:calendar-timezone on calendar collections.
24. Added XML element CALDAV:timezone to override the CALDAV:calendar-timezone property for a given CALDAV:calendar-query REPORT request.
25. Added text on the conversion of "floating date" and "floating time" values to date with UTC time values.
26. Completed internationalization considerations section.
27. Completed security considerations section.

1. Removed statement that said that client SHOULD always request DAV:getetag in calendar REPORTs.
2. Removed redefiniton of DAV:response.
3. Removed XML elements CALDAV:calendar-data-only.
4. Removed resource type CALDAV:calendar-home.
5. Moved the CALDAV:calendar-data element in the DAV:prop element in requests, and in the DAV:propstat element in responses.
6. Further defined the request body of MKCALENDAR to allow clients to set properties at calendar collection creation time.
7. Renamed CALDAV:calendar-home-URL to CALDAV:calendar-home-set
8. Clarified the fact that calendar collections may only contain calendar object resources and ordinary collections.
9. Clarified that calendar REPORTs should only be applied to calendar object resources contained in calendar collections.
10. Changed the CALDAV:calendar-component-restriction-set and CALDAV:calendar-restriction properties to always be protected.
11. Changed to use existing postcondition DAV:needs-privileges instead of a new CALDAV:insufficient-privilege postcondition.
12. Added example for limit-recurrence-set.
13. Added example for expand-recurrence-set.
14. Moved CALDAV:calendar-address-set in the calendar-schedule draft and renamed it to CALDAV:calendar-user-address-set.
15. Added guidelines on attachments and alarms.

1. Various editorial changes.
2. Added properties calendar-restrictions and calendar-component-restriction-set on calendar collections.
3. Added properties calendar-home-URL and calendar-address-set on principal resources.
4. Removed property calendar-URL on principal resources.
5. Added pre- and postconditions to reports.
6. Added new XML elements calendar-data-only and limit-recurrent-set.
7. Modified calendar-data XML element to support the attributes content-type and version.
8. Reorganised sections 3, 4, 5 & 6 into two sections and re-ordered sub-sections.
9. Added comment about client not setting a duplicate displayname.
10. Removed three CalDAV OPTIONS requests.
11. Changed "authenticated user" to "user" in various places.
12. Rewrote section on calendar object resource restrictions for better clarity.

1. Reworded section "Recurrence and the Data Model".
2. Removed timezone collection feature.
3. Removed ability for a server to return the Location header on a successful PUT request.
4. Clarified restrictions on calendar object resources contained in calendar collections.
5. Added preconditions on PUT in calendar collections.
6. Added informative "Guidelines" section, with information on locking and how to find calendar collections.
7. Moved "Sychronization Operations" section in the "Guidelines" section.

1. Removed a lot of non-normative text.
2. Removed property promotion/demotion requirements.
3. Removed calendar-owner and cal-scale properties.
4. Removed 'ical' prefix/text from element names.
5. Relaxed WebDAV Class 2 (locking) requirement to a MAY.
6. Relaxed MKCALENDAR requirement to a SHOULD.
7. Moved the XML Namespace section in the Introduction.
8. Added CALDAV: prefix to CalDAV XML elements in the text.
9. Added CALDAV:calendar-multiget report.
10. Added CALDAV:free-busy-query report.
11. Added CALDAV:calendar-description property.
12. Changed CALDAV:calendar-query-result element name to CALDAV:calendar-data
13. Added description and examples of handling timezones.
14. Added mandatory "start" and "end" attributes to the CALDAV:expand-recurrence-set element.
15. Added three CalDAV OPTIONS requests.
16. Grouped XML Element declarations in a separate section.

1. Added a note about the HTTP Location response header.
2. Added report calendar-query.
3. Removed reports calendar-property-search and calendar-time-range.
4. Removed section on CalDAV and timezones.
5. Added requirement to return ETag on creation.
6. Revised data model to remove sub-collections from calendar collection.
7. Added informative references section.
8. Removed dependencies on DASL.

1. Removed Calendar Containers (simplification that doesn't seem to remove much functionality)
2. Added MKCALENDAR to create calendars and all sub-collections
3. Added cal-scale property to calendars

Basically still adding major sections of content: ¶

1. Defined new field values to the OPTIONS "DAV:" response header
2. Added new resource properties
3. Added new principal properties
4. Added new SCHEDULE method and related headers
5. Added new privileges for scheduling

1. Added section on privileges for calendaring, extending WebDAV ACL privilege set
2. Defined what to do with unrecognized properties in the bodies of iCalendar events, with respect to property promotion/demotion