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PROPOSED STANDARD
Updated by:7953
Internet Engineering Task Force (IETF)                          C. DabooRequest for Comments: 6638                                    Apple Inc.Updates:4791,5546                                      B. DesruisseauxCategory: Standards Track                                         OracleISSN: 2070-1721                                                June 2012Scheduling Extensions to CalDAVAbstract   This document defines extensions to the Calendaring Extensions to   WebDAV (CalDAV) "calendar-access" feature to specify a standard way   of performing scheduling operations with iCalendar-based calendar   components.  This document defines the "calendar-auto-schedule"   feature of CalDAV.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6638.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Daboo & Desruisseaux         Standards Track                    [Page 1]

RFC 6638                    CalDAV Scheduling                  June 2012   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate it into languages other   than English.Table of Contents1. Introduction ....................................................51.1. Terminology ................................................61.2. Notational Conventions .....................................71.3. XML Namespaces and Processing ..............................72. Scheduling Support ..............................................82.1. Scheduling Outbox Collection ...............................92.1.1. CALDAV:schedule-outbox-URL Property ................102.2. Scheduling Inbox Collection ...............................102.2.1. CALDAV:schedule-inbox-URL Property .................112.3. Calendaring Reports Extensions ............................122.4. Additional Principal Properties ...........................122.4.1. CALDAV:calendar-user-address-set Property ..........122.4.2. CALDAV:calendar-user-type Property .................133. Scheduling Operations ..........................................143.1. Identifying Scheduling Object Resources ...................143.2. Handling Scheduling Object Resources ......................153.2.1. Organizer Scheduling Object Resources ..............153.2.1.1. Create ....................................163.2.1.2. Modify ....................................173.2.1.3. Remove ....................................183.2.2. Attendee Scheduling Object Resources ...............183.2.2.1. Allowed "Attendee" Changes ................183.2.2.2. Create ....................................193.2.2.3. Modify ....................................203.2.2.4. Remove ....................................213.2.3. HTTP Methods .......................................213.2.3.1. PUT .......................................223.2.3.2. DELETE ....................................223.2.3.3. COPY ......................................233.2.3.4. MOVE ......................................24Daboo & Desruisseaux         Standards Track                    [Page 2]

RFC 6638                    CalDAV Scheduling                  June 20123.2.4. Additional Method Preconditions ....................24                  3.2.4.1. CALDAV:unique-scheduling-object-resource                           Precondition ..............................24                  3.2.4.2. CALDAV:same-organizer-in-all-components                           Precondition ..............................25                  3.2.4.3. CALDAV:allowed-organizer-scheduling-                              object-change Precondition .............25                  3.2.4.4. CALDAV:allowed-attendee-scheduling-                              object-change Precondition .............263.2.5. DTSTAMP and SEQUENCE Properties ....................263.2.6. Restrict Recurrence Instances Sent to "Attendees" ..273.2.7. Forcing the Server to Send a Scheduling Message ....273.2.8. "Attendee" Participation Status ....................283.2.9. Schedule Status Values .............................29           3.2.10. Avoiding Conflicts when Updating Scheduling Object                   Resources .........................................313.2.10.1. PUT .....................................333.2.10.2. DELETE, COPY, or MOVE ...................334. Processing Incoming Scheduling Messages ........................34      4.1. Processing "Organizer" Requests, Additions, and           Cancellations .............................................344.2. Processing "Attendee" Replies .............................354.3. Default Calendar Collection ...............................354.3.1. Additional Method Preconditions ....................36                  4.3.1.1. CALDAV:default-calendar-needed                           Precondition ..............................36                  4.3.1.2. CALDAV:valid-schedule-default-calendar-URL                           Precondition ..............................365. Request for Busy Time Information ..............................375.1. Status Codes ..............................................385.2. Additional Method Preconditions ...........................385.2.1. CALDAV:valid-scheduling-message Precondition .......385.2.2. CALDAV:valid-organizer Precondition ................396. Scheduling Privileges ..........................................396.1. Privileges on Scheduling Inbox Collections ................396.1.1. CALDAV:schedule-deliver Privilege ..................406.1.2. CALDAV:schedule-deliver-invite Privilege ...........406.1.3. CALDAV:schedule-deliver-reply Privilege ............406.1.4. CALDAV:schedule-query-freebusy Privilege ...........406.2. Privileges on Scheduling Outbox Collections ...............406.2.1. CALDAV:schedule-send Privilege .....................416.2.2. CALDAV:schedule-send-invite Privilege ..............416.2.3. CALDAV:schedule-send-reply Privilege ...............416.2.4. CALDAV:schedule-send-freebusy Privilege ............416.3. Aggregation of Scheduling Privileges ......................42Daboo & Desruisseaux         Standards Track                    [Page 3]

RFC 6638                    CalDAV Scheduling                  June 20127. Additional iCalendar Property Parameters .......................427.1. Schedule Agent Parameter ..................................427.2. Schedule Force Send Parameter .............................447.3. Schedule Status Parameter .................................458. Additional Message Header Fields ...............................468.1. Schedule-Reply Request Header .............................468.2. Schedule-Tag Response Header ..............................468.3. If-Schedule-Tag-Match Request Header ......................479. Additional WebDAV Properties ...................................479.1. CALDAV:schedule-calendar-transp Property ..................479.2. CALDAV:schedule-default-calendar-URL Property .............489.3. CALDAV:schedule-tag Property ..............................4910. XML Element Definitions .......................................5010.1. CALDAV:schedule-response XML Element .....................5010.2. CALDAV:response XML Element ..............................5010.3. CALDAV:recipient XML Element .............................5010.4. CALDAV:request-status XML Element ........................5111. Security Considerations .......................................5111.1. Preventing Denial-of-Service Attacks .....................5111.2. Verifying Scheduling Operations ..........................5211.3. Verifying Busy Time Information Requests .................5211.4. Privacy Issues ...........................................5311.5. Mitigation of iTIP Threats ...............................5312. IANA Considerations ...........................................5412.1. Message Header Field Registrations .......................5412.1.1. Schedule-Reply ....................................5412.1.2. Schedule-Tag ......................................5412.1.3. If-Schedule-Tag-Match .............................5412.2. iCalendar Property Parameter Registrations ...............5512.3. iCalendar REQUEST-STATUS Value Registrations .............5512.4. Additional iCalendar Elements Registries .................5512.4.1. Schedule Agent Values Registry ....................5612.4.2. Schedule Force Send Values Registry ...............5613. Acknowledgements ..............................................5614. References ....................................................5714.1. Normative References .....................................5714.2. Informative References ...................................58Daboo & Desruisseaux         Standards Track                    [Page 4]

RFC 6638                    CalDAV Scheduling                  June 2012Appendix A. Scheduling Privileges Summary .........................59A.1. Scheduling Inbox Privileges ................................59A.2. Scheduling Outbox Privileges ...............................60Appendix B. Example Scheduling Operations .........................60B.1. Example: "Organizer" Inviting Multiple "Attendees" .........61B.2. Example: "Attendee" Receiving an Invitation ................63B.3. Example: "Attendee" Replying to an Invitation ..............64B.4. Example: "Organizer" Receiving a Reply to an Invitation ....66B.5. Example: "Organizer" Requesting Busy Time Information ......69     B.6. Example: User Attempting to Invite "Attendee" on          Behalf of "Organizer" ......................................71     B.7. Example: "Attendee" Declining an Instance of a          Recurring Event ............................................72     B.8. Example: "Attendee" Removing an Instance of a          Recurring Event ............................................751.  Introduction   This document specifies extensions to the CalDAV "calendar-access"   [RFC4791] feature to enable scheduling of iCalendar-based [RFC5545]   calendar components between calendar users.   This extension leverages the scheduling methods defined in the   iCalendar Transport-independent Interoperability Protocol (iTIP)   [RFC5546] to permit calendar users to perform scheduling operations   such as schedule, reschedule, respond to scheduling request, or   cancel calendar components, as well as search for busy time   information.  However, the following iTIP [RFC5546] features are not   covered: publishing, countering, delegating, refreshing, and   forwarding calendar components, as well as replacing the "Organizer"   of a calendar component.  It is expected that future extensions will   be developed to address these.   This specification defines a client/server scheduling protocol, where   the server is made responsible for sending scheduling messages and   processing incoming scheduling messages.  The client operations of   creating, modifying, or deleting a calendar component in a calendar   are enough to trigger the server to deliver the necessary scheduling   messages to the appropriate calendar users.  This approach is   sometimes referred to as "implicit scheduling".   This specification only addresses how scheduling occurs with users on   a single system (i.e., scheduling between CalDAV servers, or some   other calendaring and scheduling system, is not defined).  However,   this specification is compatible with servers being able to send or   receive scheduling messages with "external" users (e.g., using the   iCalendar Message-Based Interoperability Protocol (iMIP) [RFC6047]).Daboo & Desruisseaux         Standards Track                    [Page 5]

RFC 6638                    CalDAV Scheduling                  June 2012Section 3 defines the automated "Scheduling Operations" that allow a   client to store iCalendar data on a CalDAV server, with the server   taking specific actions in response.  One of three scheduling   operations can take place -- "create", "modify", or "remove", based   on the HTTP method used for the request -- in addition to a   comparison between any existing and any new iCalendar data.Section 4 defines how the server processes scheduling messages sent   as the result of a scheduling operation.Section 5 defines how freebusy requests with an immediate response   are accomplished.Section 6 defines access control privileges for the scheduling   operations defined in this specification.   For the majority of the following discussion, scheduling of events   will be discussed.  However, scheduling of to-dos is also fully   supported by this specification.   This specification has been under development for a number of years,   and most current implementations of CalDAV support it.  With the   publication of this document, it is expected that all new CalDAV   implementations will support it by default.  Interoperability tests   have been performed regularly.  Significant issues with incompatible   CalDAV implementations are not anticipated.1.1.  Terminology   This specification reuses much of the same terminology as iCalendar   [RFC5545], iTIP [RFC5546], WebDAV [RFC4918], and CalDAV [RFC4791].   Additional terms used by this specification are as follows:   Scheduling object resource:  A calendar object resource contained in      a calendar collection for which the server will take care of      sending scheduling messages on behalf of the owner of the calendar      collection.   Organizer scheduling object resource:  A scheduling object resource      owned by the "Organizer".   Attendee scheduling object resource:  A scheduling object resource      owned by an "Attendee".   Scheduling operation:  Add, change, or remove operations on a      scheduling object resource for which the server will deliver      scheduling messages to other calendar users.Daboo & Desruisseaux         Standards Track                    [Page 6]

RFC 6638                    CalDAV Scheduling                  June 2012   Scheduling message:  A calendar object that describes a scheduling      operation such as schedule, reschedule, reply, or cancel.   Scheduling Outbox collection:  A resource at which busy time      information requests are targeted.   Scheduling Inbox collection:  A collection in which incoming      scheduling messages are delivered.1.2.  Notational Conventions   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 Augmented BNF (ABNF) syntax used by this document to specify the   format definition of new iCalendar elements is defined in [RFC5234].   The ABNF syntax used by this document to specify the format   definition of new message header fields to be used with the HTTP/1.1   protocol is described inSection 2.1 of [RFC2616].  Since this   Augmented BNF uses the basic production rules provided inSection 2.2   of [RFC2616], these rules apply to this document as well.   The term "protected" is used in the Conformance field of WebDAV   property definitions as defined inSection 15 of [RFC4918].   Calendaring and scheduling roles are referred to in quoted-strings of   text with the first character of each word in uppercase.  For   example, "Organizer" refers to a role of a calendar user within the   scheduling protocol defined by [RFC5546].1.3.  XML Namespaces and Processing   This document uses XML DTD fragments ([W3C.REC-xml-20081126],   Section 3.2) as a purely notational convention.  WebDAV request and   response bodies cannot be validated by a DTD due to the specific   extensibility rules defined inSection 17 of [RFC4918] and due to the   fact that all XML elements defined by that specification use the XML   namespace name "DAV:".  In particular,   1.  element names use the "DAV:" namespace,   2.  element ordering is irrelevant unless explicitly stated,Daboo & Desruisseaux         Standards Track                    [Page 7]

RFC 6638                    CalDAV Scheduling                  June 2012   3.  extension elements (elements not already defined as valid child       elements) can be added anywhere, except when explicitly stated       otherwise, and   4.  extension attributes (attributes not already defined as valid for       this element) can be added anywhere, except when explicitly       stated otherwise.   The XML elements specified in this document are defined in the   "urn:ietf:params:xml:ns:caldav" XML namespace registered by CalDAV   [RFC4791].   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 strings "DAV:" and   "CALDAV:" will be prefixed to the element types, respectively.   This document inherits, and sometimes extends, DTD productions fromSection 14 of [RFC4918].   Also note that some CalDAV XML element names are identical to WebDAV   XML element names, though their namespace differs.  Care needs to be   taken not to confuse the two sets of names.2.  Scheduling Support   A server that supports the features described in this document is   REQUIRED to support the CalDAV "calendar-access" [RFC4791] feature.   Servers include "calendar-auto-schedule" as a field in the DAV   response header from an OPTIONS request on any resource that supports   any scheduling operations, properties, privileges, or methods.   This specification introduces new collection resource types that are   used to manage scheduling object resources, and scheduling privileges   (as perSection 6), as well as provide scheduling functionality.  It   is the server's responsibility to create these collection resources,   and clients have no way to create or delete them.Daboo & Desruisseaux         Standards Track                    [Page 8]

RFC 6638                    CalDAV Scheduling                  June 20122.1.  Scheduling Outbox Collection   A scheduling Outbox collection is used as the target for busy time   information requests, and to manage privileges that apply to outgoing   scheduling requests.   A scheduling Outbox collection MUST report the DAV:collection and   CALDAV:schedule-outbox XML elements in the value of the DAV:   resourcetype property.  The element type declaration for CALDAV:   schedule-outbox is     <!ELEMENT schedule-outbox EMPTY>   Example:     <D:resourcetype xmlns:D="DAV:">       <D:collection/>       <C:schedule-outbox xmlns:C="urn:ietf:params:xml:ns:caldav"/>     </D:resourcetype>   A scheduling Outbox collection MUST NOT be a child (at any depth) of   a calendar collection resource.   The following WebDAV properties specified in CalDAV "calendar-access"   [RFC4791] MAY also be defined on scheduling Outbox collections and   apply to scheduling messages submitted to the scheduling Outbox   collection with the POST method:   o  CALDAV:supported-calendar-component-set   o  CALDAV:supported-calendar-data   o  CALDAV:max-resource-size   o  CALDAV:min-date-time   o  CALDAV:max-date-time   o  CALDAV:max-attendees-per-instance   The use of child resources in a scheduling Outbox collection is   reserved for future revisions or extensions of this specification.   The following WebDAV property is defined on principal resources and   used to locate the corresponding Outbox collection for the associated   principal.Daboo & Desruisseaux         Standards Track                    [Page 9]

RFC 6638                    CalDAV Scheduling                  June 20122.1.1.  CALDAV:schedule-outbox-URL Property   Name:  schedule-outbox-URL   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Identify the URL of the scheduling Outbox collection owned      by the associated principal resource.   Protected:  This property MAY be protected.   PROPFIND behavior:  This property SHOULD NOT be returned by a      PROPFIND DAV:allprop request (as defined inSection 14.2 of      [RFC4918]).   COPY/MOVE behavior:  This property value SHOULD be preserved in COPY      and MOVE operations.   Description:  This property is needed for a client to determine where      the scheduling Outbox collection of the current user is located so      that sending of scheduling messages can occur.  If not present,      then the associated calendar user is not enabled for the sending      of scheduling messages on the server.   Definition:     <!ELEMENT schedule-outbox-URL (DAV:href)>2.2.  Scheduling Inbox Collection   A scheduling Inbox collection contains copies of incoming scheduling   messages.  These can be requests sent by an "Organizer", or replies   sent by an "Attendee" in response to a request.  The scheduling Inbox   collection is also used to manage scheduling privileges.   A scheduling Inbox collection MUST report the DAV:collection and   CALDAV:schedule-inbox XML elements in the value of the DAV:   resourcetype property.  The element type declaration for CALDAV:   schedule-inbox is     <!ELEMENT schedule-inbox EMPTY>   Example:     <D:resourcetype xmlns:D="DAV:">       <D:collection/>       <C:schedule-inbox xmlns:C="urn:ietf:params:xml:ns:caldav"/>     </D:resourcetype>Daboo & Desruisseaux         Standards Track                   [Page 10]

RFC 6638                    CalDAV Scheduling                  June 2012   Scheduling Inbox collections MUST only contain calendar object   resources that obey the restrictions specified in iTIP [RFC5546].   Consequently, scheduling Inbox collections MUST NOT contain any types   of collection resources.  Restrictions defined inSection 4.1 of   CalDAV "calendar-access" [RFC4791] on calendar object resources   contained in calendar collections (e.g., Unique Identifier ("UID")   uniqueness) do not apply to calendar object resources contained in a   scheduling Inbox collection.  Thus, multiple calendar object   resources contained in a scheduling Inbox collection can have the   same "UID" property value (i.e., multiple scheduling messages for the   same calendar component).   A scheduling Inbox collection MUST NOT be a child (at any depth) of a   calendar collection resource.   The following WebDAV properties specified in CalDAV "calendar-access"   [RFC4791] MAY also be defined on scheduling Inbox collections and   apply to scheduling messages delivered to the collection:   o  CALDAV:supported-calendar-component-set   o  CALDAV:supported-calendar-data   o  CALDAV:max-resource-size   o  CALDAV:min-date-time   o  CALDAV:max-date-time   o  CALDAV:max-instances   o  CALDAV:max-attendees-per-instance   o  CALDAV:calendar-timezone   The following WebDAV property is defined on principal resources and   used to locate the corresponding Inbox collection for the associated   principal.2.2.1.  CALDAV:schedule-inbox-URL Property   Name:  schedule-inbox-URL   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Identify the URL of the scheduling Inbox collection owned      by the associated principal resource.Daboo & Desruisseaux         Standards Track                   [Page 11]

RFC 6638                    CalDAV Scheduling                  June 2012   Protected:  This property MAY be protected.   PROPFIND behavior:  This property SHOULD NOT be returned by a      PROPFIND DAV:allprop request (as defined inSection 14.2 of      [RFC4918]).   COPY/MOVE behavior:  This property value SHOULD be preserved in COPY      and MOVE operations.   Description:  This property allows a client to determine where the      scheduling Inbox collection of the current user is located so that      processing of scheduling messages can occur.  If not present, then      the associated calendar user is not enabled for reception of      scheduling messages on the server.   Definition:     <!ELEMENT schedule-inbox-URL (DAV:href)>2.3.  Calendaring Reports Extensions   This specification extends the CALDAV:calendar-query and CALDAV:   calendar-multiget REPORTs to return results for calendar object   resources in scheduling Inbox collections.   When a CALDAV:calendar-query REPORT includes a time-range query and   targets a scheduling Inbox collection, if any calendar object   resources contain "VEVENT" calendar components that do not include a   "DTSTART" iCalendar property (as allowed by iTIP [RFC5546]) then such   components MUST always match the time-range query test.   Note that the CALDAV:free-busy-query REPORT is not supported on   scheduling Inbox collections.2.4.  Additional Principal Properties   This section defines new properties for WebDAV principal resources as   defined in [RFC3744].  These properties are likely to be protected,   but the server MAY allow them to be written by appropriate users.2.4.1.  CALDAV:calendar-user-address-set Property   Name:  calendar-user-address-set   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Identify the calendar addresses of the associated principal      resource.Daboo & Desruisseaux         Standards Track                   [Page 12]

RFC 6638                    CalDAV Scheduling                  June 2012   Protected:  This property MAY be protected.   PROPFIND behavior:  This property SHOULD NOT be returned by a      PROPFIND DAV:allprop request (as defined inSection 14.2 of      [RFC4918]).   COPY/MOVE behavior:  This property value SHOULD be preserved in COPY      and MOVE operations.   Description:  Support for this property is REQUIRED.  This property      is needed to map calendar user addresses in iCalendar data to      principal resources and their associated scheduling Inbox and      Outbox collections.  In the event that a user has no well-defined      identifier for his calendar user address, the URI of his principal      resource can be used.  This property SHOULD be searchable using      the DAV:principal-property-search REPORT.  The DAV:principal-      search-property-set REPORT SHOULD identify this property as such.      If not present, then the associated calendar user is not enabled      for scheduling on the server.   Definition:     <!ELEMENT calendar-user-address-set (DAV:href*)>   Example:     <C:calendar-user-address-set xmlns:D="DAV:"         xmlns:C="urn:ietf:params:xml:ns:caldav">       <D:href>mailto:bernard@example.com</D:href>       <D:href>mailto:bernard.desruisseaux@example.com</D:href>     </C:calendar-user-address-set>2.4.2.  CALDAV:calendar-user-type Property   Name:  calendar-user-type   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Identifies the calendar user type of the associated      principal resource.   Value:  Same values allowed for the iCalendar "CUTYPE" property      parameter defined inSection 3.2.3 of [RFC5545].   Protected:  This property MAY be protected.Daboo & Desruisseaux         Standards Track                   [Page 13]

RFC 6638                    CalDAV Scheduling                  June 2012   PROPFIND behavior:  This property SHOULD NOT be returned by a      PROPFIND DAV:allprop request (as defined inSection 14.2 of      [RFC4918]).   COPY/MOVE behavior:  This property value SHOULD be preserved in COPY      and MOVE operations.   Description:  Clients can query principal resources in order to look      up "Attendees" available on the server.  When doing this, it is      useful to know, or restrict the query to, certain types of      calendar users (e.g., only search for "people", or only search for      "rooms").  This property MAY be defined on principal resources to      indicate the type of calendar user associated with the principal      resource.  Its value is the same as the iCalendar "CUTYPE"      property parameter that can be used on "ATTENDEE" properties.      This property SHOULD be searchable using the DAV:principal-      property-search REPORT.  The DAV:principal-search-property-set      REPORT SHOULD identify this property as such.   Definition:     <!ELEMENT calendar-user-type (#PCDATA)>   Example:     <C:calendar-user-type         xmlns:C="urn:ietf:params:xml:ns:caldav">INDIVIDUAL<     /C:calendar-user-type>3.  Scheduling Operations   When a calendar object resource is created, modified, or removed from   a calendar collection, the server examines the calendar data and   checks to see whether the data represents a scheduling object   resource.  If it does, the server will automatically attempt to   deliver a scheduling message to the appropriate calendar users.   Several types of scheduling operations can occur in this case,   equivalent to iTIP "REQUEST", "REPLY", "CANCEL", and "ADD"   operations.3.1.  Identifying Scheduling Object Resources   Calendar object resources on which the server performs scheduling   operations are referred to as scheduling object resources.  There are   two types of scheduling object resources: organizer scheduling object   resources, and attendee scheduling object resources.Daboo & Desruisseaux         Standards Track                   [Page 14]

RFC 6638                    CalDAV Scheduling                  June 2012   A calendar object resource is considered to be a valid organizer   scheduling object resource if the "ORGANIZER" iCalendar property is   present and set in all the calendar components to a value that   matches one of the calendar user addresses of the owner of the   calendar collection.   A calendar object resource is considered to be a valid attendee   scheduling object resource if the "ORGANIZER" iCalendar property is   present and set in all the calendar components to the same value and   doesn't match one of the calendar user addresses of the owner of the   calendar collection, and if at least one of the "ATTENDEE" iCalendar   property values matches one of the calendar user addresses of the   owner of the calendar collection.   The creation of attendee scheduling object resources is typically   done by the server, with the resource being created in an appropriate   calendar collection (seeSection 4.3).3.2.  Handling Scheduling Object Resources   The server's behavior when processing a scheduling object resource   depends on whether it is owned by the "Organizer" or an "Attendee"   specified in the calendar data.3.2.1.  Organizer Scheduling Object Resources   An "Organizer" can create, modify, or remove a scheduling object   resource, subject to access privileges, preconditions, and the   restrictions defined inSection 4.1 of [RFC4791].  These operations   are each described next, and how they are invoked via HTTP requests   is described inSection 3.2.3.   The "Organizer" of a calendar component can also be an "Attendee" of   that calendar component.  In such cases, the server MUST NOT send a   scheduling message to the "Attendee" that matches the "Organizer".   The server SHOULD reject any attempt to set the "PARTSTAT" iCalendar   property parameter value of the "ATTENDEE" iCalendar property of   other users in the calendar object resource to a value other than   "NEEDS-ACTION" if the "SCHEDULE-AGENT" property parameter value is   not present or set to the value "SERVER".   The server MAY reject attempts to create a scheduling object resource   that specifies a "UID" property value already specified in a   scheduling object resource contained in another calendar collection   of the "Organizer".Daboo & Desruisseaux         Standards Track                   [Page 15]

RFC 6638                    CalDAV Scheduling                  June 20123.2.1.1.  Create   When an "Organizer" creates a scheduling object resource, the server   MUST inspect each "ATTENDEE" property to determine whether to send a   scheduling message.  The table below indicates the appropriate iTIP   method used by the server, taking into account any "SCHEDULE-AGENT"   property parameter (seeSection 7.1) specified on each "ATTENDEE"   property.                    +------------------+-------------+                    | SCHEDULE-AGENT   | iTIP METHOD |                    +------------------+-------------+                    | SERVER (default) | REQUEST     |                    |                  |             |                    | CLIENT           | --          |                    |                  |             |                    | NONE             | --          |                    +------------------+-------------+   "SCHEDULE-STATUS" iCalendar property parameters are added or changed   on "ATTENDEE" iCalendar properties in the scheduling object resource   being created as described inSection 7.3, with the value set as   described inSection 3.2.9.  This will result in the created calendar   object resource differing from the calendar data sent in the HTTP   request.  As a result, clients MAY reload the calendar data from the   server in order to update to the new server-generated state   information.   The server MUST add a "SCHEDULE-STATUS" iCalendar property parameter   (seeSection 7.3) to the "ATTENDEE" iCalendar property in the   scheduling object resource being created, and set its value as   described inSection 3.2.9.  This will result in the created calendar   object resource differing from the calendar data sent in the HTTP   request.  As a result, clients MAY reload the calendar data from the   server in order to update to the new server-generated state   information.  Servers MUST NOT set the "SCHEDULE-STATUS" property   parameter on the "ATTENDEE" property of "Attendees" for which it did   not attempt to deliver a scheduling message.   The server MUST return an error with the CALDAV:allowed-organizer-   scheduling-object-change precondition code (Section 3.2.4.3) when the   "Organizer" attempts to change the iCalendar data in a manner that is   forbidden.Daboo & Desruisseaux         Standards Track                   [Page 16]

RFC 6638                    CalDAV Scheduling                  June 20123.2.1.2.  Modify   When an "Organizer" modifies a scheduling object resource, the server   MUST inspect each "ATTENDEE" property in both the original and   modified iCalendar data on a per-instance basis to determine whether   to send a scheduling message.  The table below indicates the   appropriate iTIP method used by the server, taking into account any   "SCHEDULE-AGENT" property parameter (seeSection 7.1) specified on   each "ATTENDEE" property.  The values "SERVER", "CLIENT", and "NONE"   in the top and left titles of the table refer to the "SCHEDULE-AGENT"   parameter value of the "ATTENDEE" property, and the values "<Absent>"   and "<Removed>" are used to cover the cases where the "ATTENDEE"   property is not present (Original) or is being removed (Modified).   +---------------+-----------------------------------------------+   |               |                   Modified                    |   |               +-----------+-----------+-----------+-----------+   |               | <Removed> | SERVER    | CLIENT    | NONE      |   |               |           | (default) |           |           |   +===+===========+===========+===========+===========+===========+   |   | <Absent>  |  --       | REQUEST / | --        | --        |   | O |           |           | ADD       |           |           |   | r +-----------+-----------+-----------+-----------+-----------+   | i | SERVER    |  CANCEL   | REQUEST   | CANCEL    | CANCEL    |   | g | (default) |           |           |           |           |   | i +-----------+-----------+-----------+-----------+-----------+   | n | CLIENT    |  --       | REQUEST / | --        | --        |   | a |           |           | ADD       |           |           |   | l +-----------+-----------+-----------+-----------+-----------+   |   | NONE      |  --       | REQUEST / | --        | --        |   |   |           |           | ADD       |           |           |   +---+-----------+-----------+-----------+-----------+-----------+   "SCHEDULE-STATUS" iCalendar property parameters are added or changed   on "ATTENDEE" iCalendar properties in the scheduling object resource   being modified as described inSection 7.3, with the value set as   described inSection 3.2.9.  This will result in the created calendar   object resource differing from the calendar data sent in the HTTP   request.  As a result, clients MAY reload the calendar data from the   server in order to update to the new server-generated state   information.   The server MUST return an error with the CALDAV:allowed-organizer-   scheduling-object-change precondition code (Section 3.2.4.3) when the   "Organizer" attempts to change the iCalendar data in a manner that is   forbidden.Daboo & Desruisseaux         Standards Track                   [Page 17]

RFC 6638                    CalDAV Scheduling                  June 20123.2.1.3.  Remove   When an "Organizer" removes a scheduling object resource, the server   MUST inspect each "ATTENDEE" property to determine whether to send a   scheduling message.  The table below indicates the appropriate iTIP   method used by the server, taking into account any "SCHEDULE-AGENT"   property parameter (seeSection 7.1) specified on each "ATTENDEE"   property.                    +------------------+-------------+                    | SCHEDULE-AGENT   | iTIP METHOD |                    +------------------+-------------+                    | SERVER (default) | CANCEL      |                    |                  |             |                    | CLIENT           | --          |                    |                  |             |                    | NONE             | --          |                    +------------------+-------------+3.2.2.  Attendee Scheduling Object Resources   An "Attendee" can create, modify, or remove a scheduling object   resource.  These operations are each described next, and how they are   invoked via HTTP requests is described inSection 3.2.3.3.2.2.1.  Allowed "Attendee" Changes   "Attendees" are allowed to make some changes to a scheduling object   resource, though key properties such as start time, end time,   location, and summary are typically under the control of the   "Organizer".   Servers MUST allow "Attendees" to make the following iCalendar data   changes, subject to other restrictions, such as access privileges and   preconditions:   1.   change their own "PARTSTAT" iCalendar property parameter value.   2.   add, modify, or remove any "TRANSP" iCalendar properties.   3.   add, modify, or remove any "PERCENT-COMPLETE" iCalendar        properties.   4.   add, modify, or remove any "COMPLETED" iCalendar properties.   5.   add, modify, or remove any "VALARM" iCalendar components.Daboo & Desruisseaux         Standards Track                   [Page 18]

RFC 6638                    CalDAV Scheduling                  June 2012   6.   add, modify, or remove the "CALSCALE" iCalendar property within        the top-level "VCALENDAR" component.   7.   modify the "PRODID" iCalendar property within the top-level        "VCALENDAR" component.   8.   add "EXDATE" iCalendar properties and possibly remove components        for overridden recurrence instances.   9.   add, modify, or remove any "CREATED", "DTSTAMP", and        "LAST-MODIFIED" iCalendar properties.   10.  add, modify, or remove "SCHEDULE-STATUS" iCalendar property        parameters on "ATTENDEE" properties that have a "SCHEDULE-AGENT"        parameter set to "CLIENT".   11.  add new components to represent overridden recurrence instances,        provided the only changes to the recurrence instance follow the        rules above.   The server MUST return an error with the CALDAV:allowed-attendee-   scheduling-object-change precondition code (Section 3.2.4.4) when the   "Attendee" attempts to change the iCalendar data in a manner   forbidden by the server.3.2.2.2.  Create   Typically, an "Attendee" does not create scheduling object resources,   as scheduling messages delivered to him on the server are   automatically processed by the server and placed on one of his   calendars (seeSection 4).  However, in some cases, a scheduling   message can get delivered directly to the client (e.g., via email   [RFC6047]), and the "Attendee" might wish to store that on the   server.  In that case, the client creates a scheduling object   resource in a calendar belonging to the "Attendee".  It can then set   the "SCHEDULE-AGENT" iCalendar property parameter on all "ORGANIZER"   iCalendar properties in the resource to determine how the server   treats the resource.  The value of the "SCHEDULE-AGENT" iCalendar   property parameter on all "ORGANIZER" iCalendar properties MUST be   the same.Daboo & Desruisseaux         Standards Track                   [Page 19]

RFC 6638                    CalDAV Scheduling                  June 2012   +----------------+--------------------------------------------------+   | SCHEDULE-AGENT | Action                                           |   +----------------+--------------------------------------------------+   | SERVER         | The server will attempt to process changes to    |   | (default)      | the resource using the normal rules for attendee |   |                | scheduling object resources.                     |   |                |                                                  |   | CLIENT         | The server does no special processing of the     |   |                | resource.  The client is assumed to be handling  |   |                | "Attendee" replies, etc.                         |   |                |                                                  |   | NONE           | The server does no special processing of the     |   |                | resource.                                        |   +----------------+--------------------------------------------------+   "SCHEDULE-STATUS" iCalendar property parameters are added or changed   on "ORGANIZER" iCalendar properties in the scheduling object resource   being created as described inSection 7.3, with the value set as   described inSection 3.2.9.3.2.2.3.  Modify   When a scheduling object resource is modified by an "Attendee", the   server's behavior depends on the value of the "SCHEDULE-AGENT"   iCalendar property parameter on the "ORGANIZER" iCalendar properties:   +----------------+--------------------------------------------------+   | SCHEDULE-AGENT | Action                                           |   +----------------+--------------------------------------------------+   | SERVER         | The server will attempt to process the update    |   | (default)      | using the behavior listed below.                 |   |                |                                                  |   | CLIENT         | The server does no special processing of the     |   |                | resource.  The client is assumed to be handling  |   |                | any "Attendee" replies, etc.                     |   |                |                                                  |   | NONE           | The server does no special processing of the     |   |                | resource.                                        |   +----------------+--------------------------------------------------+   The server will inspect the changes by comparing the new scheduling   object resource with the existing scheduling object resource.   If the "Attendee" changes one or more "PARTSTAT" iCalendar property   values on any component, or adds an overridden component with a   changed "PARTSTAT" property, then the server MUST deliver an iTIP   "REPLY" scheduling message to the "Organizer" to indicate the new   participation status of the "Attendee".Daboo & Desruisseaux         Standards Track                   [Page 20]

RFC 6638                    CalDAV Scheduling                  June 2012   If the "Attendee" adds an "EXDATE" property value to effectively   remove a recurrence instance, the server MUST deliver an iTIP "REPLY"   scheduling message to the "Organizer" to indicate that the "Attendee"   has declined the instance.   "SCHEDULE-STATUS" iCalendar property parameters are added or changed   on "ORGANIZER" iCalendar properties in the scheduling object resource   being modified as described inSection 7.3, with the value set as   described inSection 3.2.9.  This will result in the updated calendar   object resource differing from the calendar data sent in the HTTP   request.  As a result, clients MAY reload the calendar data from the   server in order to update to the new server-generated state   information.3.2.2.4.  Remove   When a scheduling object resource is removed by an "Attendee", the   server's behavior depends on the value of the "SCHEDULE-AGENT"   iCalendar property parameter on the "ORGANIZER" iCalendar properties:   +----------------+--------------------------------------------------+   | SCHEDULE-AGENT | Action                                           |   +----------------+--------------------------------------------------+   | SERVER         | The server will attempt to process the removal,  |   | (default)      | taking into account any "Schedule-Reply" request |   |                | header as perSection 8.1.                       |   |                |                                                  |   | CLIENT         | The server does no special processing of the     |   |                | resource.  The client is assumed to be handling  |   |                | any "Attendee" replies, etc.                     |   |                |                                                  |   | NONE           | The server does no special processing of the     |   |                | resource.                                        |   +----------------+--------------------------------------------------+3.2.3.  HTTP Methods   This section describes how the use of various HTTP [RFC2616] and   WebDAV [RFC4918] methods on a scheduling object resource will cause a   create, modify, or remove operation on that resource as described   above.  The use of these methods is subject to the restrictions in   [RFC4791], in addition to what is described below.Daboo & Desruisseaux         Standards Track                   [Page 21]

RFC 6638                    CalDAV Scheduling                  June 20123.2.3.1.  PUT   When the server receives a PUT method request, it MUST execute the   following operations, provided all appropriate preconditions are met:   +------------------------+--------------------------+---------------+   | Existing Destination   | Resulting Destination    | Server        |   | Resource               | Resource                 | Operation     |   +------------------------+--------------------------+---------------+   | None                   | Calendar object resource | None          |   |                        |                          |               |   | None                   | Scheduling object        | Create        |   |                        | resource                 |               |   |                        |                          |               |   | Calendar object        | Calendar object resource | None          |   | resource               |                          |               |   |                        |                          |               |   | Calendar object        | Scheduling object        | Create        |   | resource               | resource                 |               |   | Scheduling object      | Calendar object resource | Remove        |   | resource               |                          |               |   |                        |                          |               |   | Scheduling object      | Scheduling object        | Modify        |   | resource               | resource                 |               |   +------------------------+--------------------------+---------------+3.2.3.2.  DELETE   When the server receives a DELETE method request targeted at a   scheduling object resource, it MUST execute the Remove operation.   When the server receives a DELETE method request targeted at a   calendar collection, it MUST execute the Remove operation on all   scheduling object resources contained in the calendar collection.Daboo & Desruisseaux         Standards Track                   [Page 22]

RFC 6638                    CalDAV Scheduling                  June 20123.2.3.3.  COPY   When the server receives a COPY method request, it MUST execute the   following operations based on the source and destination collections   in the request:   +-----------------------+------------------------+------------------+   | Source Collection     | Destination Collection | Server Operation |   +-----------------------+------------------------+------------------+   | Non-calendar          | Non-calendar           | None             |   | collection            | collection             |                  |   |                       |                        |                  |   | Non-calendar          | Calendar collection    | (1)              |   | collection            |                        |                  |   |                       |                        |                  |   | Calendar collection   | Non-calendar           | None             |   |                       | collection             |                  |   |                       |                        |                  |   | Calendar collection   | Calendar collection    | (2)              |   +-----------------------+------------------------+------------------+   Note (1):  The rules inSection 3.2.3.1 are applied for the              destination of the COPY request.   Note (2):  The server MAY reject this as perSection 3.2.4.1;              otherwise, None.   The behavior of a COPY method request on a calendar collection is   undefined.Daboo & Desruisseaux         Standards Track                   [Page 23]

RFC 6638                    CalDAV Scheduling                  June 20123.2.3.4.  MOVE   When the server receives a MOVE method request, it MUST execute the   following operations based on the source and destination collections   in the request:   +-----------------------+------------------------+------------------+   | Source Collection     | Destination Collection | Server Operation |   +-----------------------+------------------------+------------------+   | Non-calendar          | Non-calendar           | None             |   | collection            | collection             |                  |   |                       |                        |                  |   | Non-calendar          | Calendar collection    | (1)              |   | collection            |                        |                  |   |                       |                        |                  |   | Calendar collection   | Non-calendar           | (2)              |   |                       | collection             |                  |   |                       |                        |                  |   | Calendar collection   | Calendar collection    | None             |   +-----------------------+------------------------+------------------+   Note (1):  The rules inSection 3.2.3.1 are applied for the              destination of the MOVE request.   Note (2):  The rules inSection 3.2.3.2 are applied for the source of              the MOVE request.   The behavior of a MOVE method request on a calendar collection is   undefined.3.2.4.  Additional Method Preconditions   This specification defines method preconditions (seeSection 16 of   WebDAV [RFC4918]), in addition to those in [RFC4791], to provide   machine-parseable information in error responses.3.2.4.1.  CALDAV:unique-scheduling-object-resource Precondition   Name:  unique-scheduling-object-resource   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  PUT, COPY, and MOVE   Use with:  403 ForbiddenDaboo & Desruisseaux         Standards Track                   [Page 24]

RFC 6638                    CalDAV Scheduling                  June 2012   Purpose:  (precondition) -- Servers MAY reject requests to create a      scheduling object resource with an iCalendar "UID" property value      already in use by another scheduling object resource owned by the      same user in other calendar collections.  Servers SHOULD report      the URL of the scheduling object resource that is already making      use of the same "UID" property value in the DAV:href element.   Definition:     <!ELEMENT unique-scheduling-object-resource (DAV:href?)>   Example:     <C:unique-scheduling-object-resource xmlns:D="DAV:"         xmlns:C="urn:ietf:params:xml:ns:caldav">       <D:href>/home/bernard/calendars/personal/abc123.ics</D:href>     </C:unique-scheduling-object-resource>3.2.4.2.  CALDAV:same-organizer-in-all-components Precondition   Name:  same-organizer-in-all-components   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  PUT, COPY, and MOVE   Use with:  403 Forbidden   Purpose:  (precondition) -- All the calendar components in a      scheduling object resource MUST contain the same "ORGANIZER"      property value when present.   Definition:     <!ELEMENT same-organizer-in-all-components EMPTY>3.2.4.3.  CALDAV:allowed-organizer-scheduling-object-change Precondition   Name:  allowed-organizer-scheduling-object-change   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  PUT, COPY, and MOVE   Use with:  403 ForbiddenDaboo & Desruisseaux         Standards Track                   [Page 25]

RFC 6638                    CalDAV Scheduling                  June 2012   Purpose:  (precondition) -- Servers MAY impose restrictions on      modifications allowed by an "Organizer".  For instance, servers      MAY prevent the "Organizer" from setting the "PARTSTAT" property      parameter to a value other than "NEEDS-ACTION" if the      corresponding "ATTENDEE" property has the "SCHEDULE-AGENT"      property parameter set to "SERVER", or does not have the      "SCHEDULE-AGENT" property parameter.  SeeSection 3.2.1.   Definition:     <!ELEMENT allowed-organizer-scheduling-object-change EMPTY>3.2.4.4.  CALDAV:allowed-attendee-scheduling-object-change Precondition   Name:  allowed-attendee-scheduling-object-change   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  PUT, COPY, and MOVE   Use with:  403 Forbidden   Purpose:  (precondition) -- Servers MAY impose restrictions on      modifications allowed by an "Attendee", subject to the allowed      changes specified inSection 3.2.2.1.   Definition:     <!ELEMENT allowed-attendee-scheduling-object-change EMPTY>3.2.5.  DTSTAMP and SEQUENCE Properties   The server MUST ensure that a "DTSTAMP" iCalendar property is present   and set the value to the UTC time that the scheduling message was   generated (as required by iCalendar).   The server MUST ensure that for each type of scheduling operation,   the "SEQUENCE" iCalendar property value is updated as per iTIP   [RFC5546].Daboo & Desruisseaux         Standards Track                   [Page 26]

RFC 6638                    CalDAV Scheduling                  June 20123.2.6.  Restrict Recurrence Instances Sent to "Attendees"   Servers MUST ensure that "Attendees" only get information about   recurrence instances that explicitly include them as an "Attendee",   when delivering scheduling messages for recurring calendar   components.   For example, if an "Attendee" is invited to only a single instance of   a recurring event, the organizer scheduling object resource will   contain an overridden instance in the form of a separate calendar   component.  That separate calendar component will include the   "ATTENDEE" property referencing the "one-off" "Attendee".  That   "Attendee" will not be listed in any other calendar components in the   scheduling object resource.  Any scheduling messages delivered to the   "Attendee" will only contain information about this overridden   instance.   As another example, an "Attendee" could be excluded from one instance   of a recurring event.  In that case, the organizer scheduling object   resource will include an overridden instance with an "ATTENDEE" list   that does not include the "Attendee" being excluded.  Any scheduling   messages delivered to the "Attendee" will not specify the overridden   instance but rather will include an "EXDATE" property in the "master"   component that defines the recurrence set.3.2.7.  Forcing the Server to Send a Scheduling Message   The iCalendar property parameter "SCHEDULE-FORCE-SEND", defined inSection 7.2, can be used by a calendar user to force the server to   send a scheduling message to an "Attendee" or the "Organizer" in a   situation where the server would not normally send a scheduling   message.  For instance, an "Organizer" could use this property   parameter to request an "Attendee" that previously declined an   invitation to reconsider his participation status without being   forced to modify the event.Daboo & Desruisseaux         Standards Track                   [Page 27]

RFC 6638                    CalDAV Scheduling                  June 20123.2.8.  "Attendee" Participation Status   This section specifies additional requirements on the handling of the   "PARTSTAT" property parameter when the "SCHEDULE-AGENT" property   parameter on the corresponding "ATTENDEE" property is set to the   value "SERVER" or is not present.   A reschedule occurs when any "DTSTART", "DTEND", "DURATION", "DUE",   "RRULE", "RDATE", or "EXDATE" property changes in a calendar   component such that existing recurrence instances are impacted by the   changes, as shown in the table below.  Servers MUST reset the   "PARTSTAT" property parameter value of all "ATTENDEE" properties,   except the one that corresponds to the "Organizer", to "NEEDS-ACTION"   for each calendar component change that causes any instance to be   rescheduled.   +-----------+-------------------------------------------------------+   | Property  | Server Action                                         |   +-----------+-------------------------------------------------------+   | DTSTART,  | Any change to these properties results in "PARTSTAT"  |   | DTEND,    | being set to "NEEDS-ACTION".                          |   | DURATION, |                                                       |   | DUE       |                                                       |   |           |                                                       |   | RRULE     | A change to or addition of this property that results |   |           | in the addition of new recurring instances or a       |   |           | change in time for existing recurring instances       |   |           | results in "PARTSTAT" being reset to "NEEDS-ACTION"   |   |           | on each affected component.                           |   |           |                                                       |   | RDATE     | A change to or addition of this property that results |   |           | in the addition of new recurring instances or a       |   |           | change in time for existing recurring instances       |   |           | results in "PARTSTAT" being reset to "NEEDS-ACTION"   |   |           | on each affected component.                           |   |           |                                                       |   | EXDATE    | A change to or removal of this property that results  |   |           | in the reinstatement of recurring instances results   |   |           | in "PARTSTAT" being set to "NEEDS-ACTION" on each     |   |           | affected component.                                   |   +-----------+-------------------------------------------------------+   The server MAY allow the "Organizer's" client to change an   "Attendee's" "PARTSTAT" property parameter value to "NEEDS-ACTION" at   any other time (e.g., when the "LOCATION" property value changes, an   "Organizer" might wish to re-invite "Attendees" who might be impacted   by the change).Daboo & Desruisseaux         Standards Track                   [Page 28]

RFC 6638                    CalDAV Scheduling                  June 20123.2.9.  Schedule Status Values   When scheduling with an "Attendee", there are two types of status   information that can be returned during the operation.  The first   type of status information is a "delivery" status that indicates   whether the scheduling message from the "Organizer" to the "Attendee"   was delivered or not, or what the current status of delivery is.  The   second type of status information is a "reply" status corresponding   to the "Attendee's" own "REQUEST-STATUS" information from the   scheduling message reply that is sent back to the "Organizer".   Similarly, when an "Attendee" sends a reply back to the "Organizer",   there will be "delivery" status information for the scheduling   message sent to the "Organizer".  However, there is no   "REQUEST-STATUS" sent back by the "Organizer", so there is no   equivalent of the "reply" status as per scheduling messages to   "Attendees".   The "delivery" status information on an "ORGANIZER" or "ATTENDEE"   iCalendar property is conveyed in the "SCHEDULE-STATUS" property   parameter value (Section 7.3).  The status code value for "delivery"   status can be one of the following:   +----------+--------------------------------------------------------+   | Delivery | Description                                            |   | Status   |                                                        |   | Code     |                                                        |   +----------+--------------------------------------------------------+   | 1.0      | The scheduling message is pending.  That is, the       |   |          | server is still in the process of sending the message. |   |          | The status code value can be expected to change once   |   |          | the server has completed its sending and delivery      |   |          | attempts.                                              |   |          |                                                        |   | 1.1      | The scheduling message has been successfully sent.     |   |          | However, the server does not have explicit information |   |          | about whether the scheduling message was successfully  |   |          | delivered to the recipient.  This state can occur with |   |          | "store and forward" style scheduling protocols such as |   |          | iMIP [RFC6047] (iTIP using email).                     |   |          |                                                        |   | 1.2      | The scheduling message has been successfully           |   |          | delivered.                                             |   |          |                                                        |Daboo & Desruisseaux         Standards Track                   [Page 29]

RFC 6638                    CalDAV Scheduling                  June 2012   | 3.7      | The scheduling message was not delivered because the   |   |          | server did not recognize the calendar user address as  |   |          | a valid calendar user.  Note that this code applies to |   |          | both "Organizer" and "Attendee" calendar user          |   |          | addresses.                                             |   |          |                                                        |   | 3.8      | The scheduling message was not delivered due to        |   |          | insufficient privileges.  Note that this code applies  |   |          | to privileges granted by both the "Organizer" and      |   |          | "Attendee" calendar users.                             |   |          |                                                        |   | 5.1      | The scheduling message was not delivered because the   |   |          | server could not complete delivery of the message.     |   |          | This is likely due to a temporary failure, and the     |   |          | originator can try to send the message again at a      |   |          | later time.                                            |   |          |                                                        |   | 5.2      | The scheduling message was not delivered because the   |   |          | server was not able to find a way to deliver the       |   |          | message.  This is likely a permanent failure, and the  |   |          | originator ought not try to send the message again, at |   |          | least without verifying/correcting the calendar user   |   |          | address of the recipient.                              |   |          |                                                        |   | 5.3      | The scheduling message was not delivered and was       |   |          | rejected because scheduling with that recipient is not |   |          | allowed.  This is likely a permanent failure, and the  |   |          | originator ought not try to send the message again.    |   +----------+--------------------------------------------------------+   The status code for "reply" status can be any of the valid iTIP   [RFC5546] "REQUEST-STATUS" values.   The 1.xx "REQUEST-STATUS" codes are new.  This specification modifies   item (2) ofSection 3.6 of [RFC5546] by adding the following   restriction:      For a 1.xx code, all components MUST have exactly the same code.Daboo & Desruisseaux         Standards Track                   [Page 30]

RFC 6638                    CalDAV Scheduling                  June 2012   Definition of the new 1.xx codes is as follows:3.2.9.1.  Status Code 1.0   Status Code:  1.0   Status Description:  Pending.   Status Exception Data:  None.   Description:  Delivery of the iTIP message is pending.3.2.9.2.  Status Code 1.1   Status Code:  1.1   Status Description:  Sent.   Status Exception Data:  None.   Description:  The iTIP message has been sent, though no information      about successful delivery is known.3.2.9.3.  Status Code 1.2   Status Code:  1.2   Status Description:  Delivered.   Status Exception Data:  None.   Description:  The iTIP message has been sent and delivered.3.2.10.  Avoiding Conflicts when Updating Scheduling Object Resources   Scheduling object resources on the server might change frequently as   "Attendees" change their participation status, triggering updates to   the "Organizer", and refreshes of other "Attendees'" copies of the   scheduling object resource.  This can lead to an "inconsequential"   change to a calendar user's data -- one that does not directly impact   the user's own participation status.  When this occurs, clients have   to reload calendar data and reconcile with changes being made by   calendar users.  To avoid the need for this, the server can instead   merge calendar data changes from a client with changes made as a   result of a scheduling operation carried out by some other calendar   user.Daboo & Desruisseaux         Standards Track                   [Page 31]

RFC 6638                    CalDAV Scheduling                  June 2012   This specification introduces a new WebDAV resource property CALDAV:   schedule-tag with a corresponding response header "Schedule-Tag", and   a new "If-Schedule-Tag-Match" request header to allow client changes   to be appropriately merged with server changes in the case where the   changes on the server were the result of an "inconsequential"   scheduling message update (one that simply updates the status   information of "Attendees" due to a reply from another "Attendee").   Servers MUST automatically resolve conflicts with "inconsequential"   changes done to scheduling object resources when the "If-Schedule-   Tag-Match" request header is specified.  The If-Schedule-Tag-Match   request header applies only to the Request-URI, and not to the   destination of a COPY or MOVE.   A response to any successful GET or PUT request targeting a   scheduling object resource MUST include a Schedule-Tag response   header with the value set to the same value as the CALDAV:schedule-   tag WebDAV property of the resource.   A response to any successful COPY or MOVE request that specifies a   Destination request header targeting a scheduling object resource   MUST include a Schedule-Tag response header with the value set to the   same value as the CALDAV:schedule-tag WebDAV property of the   destination resource.   Clients SHOULD use the If-Schedule-Tag-Match header on requests that   update scheduling object resources, instead of HTTP ETag-based   precondition tests (e.g., If-Match).  Normal ETag-based precondition   tests are used in all other cases, e.g., for synchronization.   The value of the CALDAV:schedule-tag property changes according to   these rules:   o  For an "Organizer's" copy of a scheduling object resource:      1.  The server MUST NOT change the CALDAV:schedule-tag property          value when the scheduling object resource is updated as the          result of automatically processing a scheduling message reply          from an "Attendee".  For instance, when an "Attendee" replies          to the "Organizer", the CALDAV:schedule-tag property is          unchanged after the "Organizer's" scheduling object resource          has been automatically updated by the server with the          "Attendee's" new participation status.      2.  The server MUST change the CALDAV:schedule-tag property value          when the scheduling object resource is changed directly via an          HTTP request (e.g., PUT, COPY, or MOVE).Daboo & Desruisseaux         Standards Track                   [Page 32]

RFC 6638                    CalDAV Scheduling                  June 2012   o  For an "Attendee's" copy of a scheduling object resource:      1.  The server MUST change the CALDAV:schedule-tag property value          when the scheduling object resource is changed as the result          of processing a scheduling message update from an "Organizer"          that contains changes other than just the participation status          of "Attendees".      2.  The server MUST NOT change the CALDAV:schedule-tag property          value when the scheduling object resource is changed as the          result of processing a scheduling message update from an          "Organizer" that only specifies changes in the participation          status of "Attendees".  For instance, when "Attendee" "A"          replies to "Organizer" "O", and "Attendee" "B" receives a          scheduling message update from "Organizer" "O" with the new          participation status of "Attendee" "A", the CALDAV:schedule-          tag property of "Attendee" "B"'s scheduling object resource          would remain the same.      3.  The server MUST change the CALDAV:schedule-tag property value          when the scheduling object resource is changed directly via an          HTTP request (e.g., PUT, COPY, or MOVE).3.2.10.1.  PUT   Clients MAY use the If-Schedule-Tag-Match request header to do a PUT   request that ensures that "inconsequential" changes on the server do   not result in a precondition error.  The value of the request header   is set to the last Schedule-Tag value received for the resource being   modified.  If the value of the If-Schedule-Tag-Match header matches   the current value of the CALDAV:schedule-tag property, the server   MUST take any "ATTENDEE" property changes for all "Attendees" other   than the owner of the scheduling object resource and apply those to   the new resource being stored.  Otherwise, the server MUST fail the   request with a 412 Precondition Failed status code.3.2.10.2.  DELETE, COPY, or MOVE   Clients MAY use the If-Schedule-Tag-Match request header to do a   DELETE, COPY, or MOVE request that ensures that "inconsequential"   changes on the server do not result in a precondition error.  The   value of the request header is set to the last Schedule-Tag value   received for the resource being deleted.  If the value of the   If-Schedule-Tag-Match header matches the current value of the CALDAV:   schedule-tag property, the server performs the normal DELETE, COPY,   or MOVE request processing for the resource.  Otherwise, the server   MUST fail the request with a 412 Precondition Failed status code.Daboo & Desruisseaux         Standards Track                   [Page 33]

RFC 6638                    CalDAV Scheduling                  June 20124.  Processing Incoming Scheduling Messages   Scheduling operations can cause the delivery of a scheduling message   into an "Organizer's" or "Attendee's" scheduling Inbox collection.   Servers MUST automatically process incoming scheduling messages using   the rules defined by [RFC5546], by creating or updating the   corresponding scheduling object resources on calendars owned by the   owner of the scheduling Inbox collection.  In addition, the   scheduling message is stored in the scheduling Inbox collection as an   indicator to the client that a scheduling operation has taken place.   Scheduling messages are typically removed from the scheduling Inbox   collection by the client once the calendar user has acknowledged the   change.   The server MUST take into account privileges on the scheduling Inbox   collection when processing incoming scheduling messages, to determine   whether delivery of the scheduling message is allowed.  Privileges on   calendars containing any matching scheduling object resource are not   considered in this case (i.e., a schedule message from another user   can cause modifications to resources in calendar collections that the   other user would not normally have read or write access to).   Additionally, servers MUST take into account any scheduling Inbox   collection preconditions (seeSection 2.2) when delivering the   scheduling message, and MUST take into account the similar   preconditions on any calendar collection that contains, or would   contain, the corresponding scheduling object resource.4.1.  Processing "Organizer" Requests, Additions, and Cancellations   For a scheduling message sent by an "Organizer", the server first   tries to locate a corresponding scheduling object resource belonging   to the "Attendee".  If no matching scheduling object resource exists,   the server treats the scheduling message as a new message; otherwise,   it is treated as an update.   In the case of a new message, the server processes the scheduling   message and creates a new scheduling object resource as perSection 4.3.   In the case of an update, the server processes the scheduling message   and updates the matching scheduling object resource belonging to the   "Attendee" to reflect the changes sent by the "Organizer".   In each case, the scheduling message MUST only appear in the   "Attendee's" scheduling Inbox collection once all automatic   processing has been done.Daboo & Desruisseaux         Standards Track                   [Page 34]

RFC 6638                    CalDAV Scheduling                  June 20124.2.  Processing "Attendee" Replies   For a scheduling message reply sent by an "Attendee", the server   first locates the corresponding scheduling object resource belonging   to the "Organizer".  If the corresponding scheduling object resource   cannot be found, the server SHOULD ignore the scheduling message.   The server MUST then update the "PARTSTAT" iCalendar property   parameter value of each "ATTENDEE" iCalendar property in the   scheduling object resource to match the changes indicated in the   reply (taking into account the fact that an "Attendee" could have   created a new overridden iCalendar component to indicate different   participation status on one or more instances of a recurring event).   The server MUST also update or add the "SCHEDULE-STATUS" property   parameter on each matching "ATTENDEE" iCalendar property and set its   value to that of the "REQUEST-STATUS" property in the reply, or to   "2.0" if "REQUEST-STATUS" is not present (also taking into account   recurrence instances).  If there are multiple "REQUEST-STATUS"   properties in the reply, the "SCHEDULE-STATUS" property parameter   value is set to a comma-separated list of status codes, one from each   "REQUEST-STATUS" property.   The server SHOULD send scheduling messages to all the other   "Attendees" indicating the change in participation status of the   "Attendee" replying, subject to the recurrence requirements ofSection 3.2.6.   The scheduling message MUST only appear in the "Organizer's"   scheduling Inbox collection once all automatic processing has been   done.4.3.  Default Calendar Collection   The server processes scheduling messages received for an "Attendee"   by creating a new scheduling object resource in a calendar collection   belonging to the "Attendee", when one does not already exist.  A   calendar user that is an "Attendee" in a scheduling operation MUST   have at least one valid calendar collection available.  If there is   no valid calendar collection, then the server MUST reject the attempt   to deliver the scheduling message to the "Attendee".   Servers MAY provide support for a default calendar collection -- that   is, the calendar collection in which new scheduling object resources   will be created.  The CALDAV:schedule-default-calendar-URL WebDAV   property, which can be present on the scheduling Inbox collection of   a calendar user, specifies whether this calendar user has a default   calendar collection.  SeeSection 9.2.Daboo & Desruisseaux         Standards Track                   [Page 35]

RFC 6638                    CalDAV Scheduling                  June 2012   Servers SHOULD create new scheduling object resources in the default   calendar collection, if the CALDAV:schedule-default-calendar-URL   WebDAV property is set.   Servers MAY allow clients to change the default calendar collection   by changing the value of the CALDAV:schedule-default-calendar-URL   WebDAV property on the scheduling Inbox collection.  However, the   server MUST ensure that any new value for that property refers to a   valid calendar collection belonging to the owner of the scheduling   Inbox collection.   Servers MUST reject any attempt to delete the default calendar   collection.4.3.1.  Additional Method Preconditions   This specification defines additional method preconditions (seeSection 16 of WebDAV [RFC4918]) to provide machine-parseable   information in error responses.4.3.1.1.  CALDAV:default-calendar-needed Precondition   Name:  default-calendar-needed   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  DELETE   Use with:  403 Forbidden   Purpose:  (precondition) -- The client attempted to delete the      calendar collection currently referenced by the CALDAV:schedule-      default-calendar-URL property, or attempted to remove the CALDAV:      schedule-default-calendar-URL property on the scheduling Inbox      collection on a server that doesn't allow such operations.   Definition:     <!ELEMENT default-calendar-needed EMPTY>4.3.1.2.  CALDAV:valid-schedule-default-calendar-URL Precondition   Name:  valid-schedule-default-calendar-URL   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  PROPPATCHDaboo & Desruisseaux         Standards Track                   [Page 36]

RFC 6638                    CalDAV Scheduling                  June 2012   Use with:  403 Forbidden   Purpose:  (precondition) -- The client attempted to set the CALDAV:      schedule-default-calendar-URL property to a DAV:href element that      doesn't reference a valid calendar collection.  Note: Servers that      do not allow clients to change the CALDAV:schedule-default-      calendar-URL property would simply return the DAV:cannot-modify-      protected-property precondition defined inSection 16 of WebDAV      [RFC4918].   Definition:     <!ELEMENT valid-schedule-default-calendar-URL EMPTY>5.  Request for Busy Time Information   Busy time information of one or more calendar users can be determined   by submitting a POST request targeted at the scheduling Outbox   collection of the calendar user requesting the information (the   "Organizer").  To accomplish this, the request body MUST contain a   "VFREEBUSY" calendar component with the "METHOD" iCalendar property   set to the value "REQUEST" as specified inSection 3.3.2 of iTIP   [RFC5546].  The resource identified by the Request-URI MUST be a   resource collection of type CALDAV:schedule-outbox (Section 2.1).   The "ORGANIZER" property value in the "VFREEBUSY" component MUST   match one of the calendar user addresses of the owner of the Outbox   collection.   A response to a busy time request that indicates status for one or   more calendar users MUST be an XML document with a CALDAV:schedule-   response XML element as its root element.  This element MUST contain   one CALDAV:response element for each calendar user, with each such   element in turn containing elements that indicate which calendar user   they correspond to, the scheduling status for that calendar user, any   error codes, and an optional description.  For a successful busy time   request, a CALDAV:calendar-data element is also present for each   calendar user, containing the actual busy time information (i.e., an   iCalendar "VFREEBUSY" component).  SeeSection 10 for details on the   child elements.  SeeAppendix B.5 for an example busy time request   and response.Daboo & Desruisseaux         Standards Track                   [Page 37]

RFC 6638                    CalDAV Scheduling                  June 20125.1.  Status Codes   The list below summarizes the most common status codes used for this   method.  However, clients need to be prepared to handle other   2/3/4/5xx series status codes as well.      200 (OK) - The command succeeded.      204 (No Content) - The command succeeded.      400 (Bad Request) - The client has provided an invalid scheduling      message.      403 (Forbidden) - The client cannot submit a scheduling message to      the specified Request-URI.      404 (Not Found) - The URL in the Request-URI was not present.      423 (Locked) - The specified resource is locked, and the client      either is not a lock owner or the lock type requires a lock token      to be submitted and the client did not submit it.5.2.  Additional Method Preconditions   The following are existing preconditions that are reused for the POST   method on an Outbox collection.   o  DAV:need-privileges [RFC3744]   o  CALDAV:supported-calendar-data [RFC4791]   o  CALDAV:valid-calendar-data [RFC4791]   o  CALDAV:max-resource-size [RFC4791]   The following are new method preconditions for the POST method on an   Outbox collection.5.2.1.  CALDAV:valid-scheduling-message Precondition   Name:  valid-scheduling-message   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  POST   Use with:  400 Bad RequestDaboo & Desruisseaux         Standards Track                   [Page 38]

RFC 6638                    CalDAV Scheduling                  June 2012   Purpose:  (precondition) -- The resource submitted in the POST      request MUST obey all the restrictions specified inSection 3.3.2      of iTIP [RFC5546].   Definition:     <!ELEMENT valid-scheduling-message EMPTY>5.2.2.  CALDAV:valid-organizer Precondition   Name:  valid-organizer   Namespace:  urn:ietf:params:xml:ns:caldav   Apply to:  POST   Use with:  403 Forbidden   Purpose:  (precondition) -- The "ORGANIZER" property value in the      POST request's scheduling message MUST match one of the calendar      user addresses of the owner of the scheduling Outbox collection      being targeted by the request.   Definition:     <!ELEMENT valid-organizer EMPTY>6.  Scheduling Privileges   New scheduling privileges are defined in this section.  All the   scheduling privileges MUST be non-abstract and MUST appear in the   DAV:supported-privilege-set property of scheduling Outbox and Inbox   collections on which they are defined.   The tables specified inAppendix A clarify which scheduling methods   (e.g., "REQUEST", "REPLY", etc.) are controlled by each scheduling   privilege defined in this section.6.1.  Privileges on Scheduling Inbox Collections   This section defines new WebDAV Access Control List (ACL) [RFC3744]   privileges that are defined for use on scheduling Inbox collections.   These privileges determine whether delivery of scheduling messages   from a calendar user is allowed by the calendar user who "owns" the   scheduling Inbox collection.  This allows calendar users to choose   which other calendar users can schedule with them.Daboo & Desruisseaux         Standards Track                   [Page 39]

RFC 6638                    CalDAV Scheduling                  June 2012   Note that when a scheduling message is delivered to a calendar user,   in addition to a scheduling object resource being created in the   calendar user's scheduling Inbox collection, a new scheduling object   resource might be created or an existing one updated in a calendar   belonging to the calendar user.  In that case, the ability to create   or update the scheduling object resource in the calendar is   controlled by the privileges assigned to the scheduling Inbox   collection.   The privileges defined in this section are ignored if applied to a   resource other than a scheduling Inbox collection.6.1.1.  CALDAV:schedule-deliver Privilege   CALDAV:schedule-deliver is an aggregate privilege as perSection 6.3.     <!ELEMENT schedule-deliver EMPTY>6.1.2.  CALDAV:schedule-deliver-invite Privilege   The CALDAV:schedule-deliver-invite privilege controls the processing   and delivery of scheduling messages coming from an "Organizer".     <!ELEMENT schedule-deliver-invite EMPTY>6.1.3.  CALDAV:schedule-deliver-reply Privilege   The CALDAV:schedule-deliver-reply privilege controls the processing   and delivery of scheduling messages coming from an "Attendee".     <!ELEMENT schedule-deliver-reply EMPTY>6.1.4.  CALDAV:schedule-query-freebusy Privilege   The CALDAV:schedule-query-freebusy privilege controls freebusy   requests targeted at the owner of the scheduling Inbox collection.     <!ELEMENT schedule-query-freebusy EMPTY>6.2.  Privileges on Scheduling Outbox Collections   This section defines new WebDAV ACL [RFC3744] privileges that are   defined for use on scheduling Outbox collections.  These privileges   determine which calendar users are allowed to send scheduling   messages on behalf of the calendar user who "owns" the scheduling   Outbox collection.  This allows calendar users to choose other   calendar users who can act on their behalf (e.g., assistants working   on behalf of their boss).Daboo & Desruisseaux         Standards Track                   [Page 40]

RFC 6638                    CalDAV Scheduling                  June 2012   The privileges defined in this section are ignored if applied to a   resource other than a scheduling Outbox collection.6.2.1.  CALDAV:schedule-send Privilege   CALDAV:schedule-send is an aggregate privilege as perSection 6.3.     <!ELEMENT schedule-send EMPTY>6.2.2.  CALDAV:schedule-send-invite Privilege   The CALDAV:schedule-send-invite privilege controls the sending of   scheduling messages by "Organizers".   Users granted the DAV:bind privilege on a calendar collection, or the   DAV:write privilege on scheduling object resources, will also need   the CALDAV:schedule-send-invite privilege granted on the scheduling   Outbox collection of the owner of the calendar collection or   scheduling object resource in order to be allowed to create, modify,   or delete scheduling object resources in a way that will trigger the   CalDAV server to deliver scheduling messages to "Attendees".     <!ELEMENT schedule-send-invite EMPTY>6.2.3.  CALDAV:schedule-send-reply Privilege   The CALDAV:schedule-send-reply privilege controls the sending of   scheduling messages by "Attendees".   Users granted the DAV:bind privilege on a calendar collection, or the   DAV:write privilege on scheduling object resources, will also need   the CALDAV:schedule-send-reply privilege granted on the scheduling   Outbox collection of the owner of the calendar collection or   scheduling object resource in order to be allowed to create, modify,   or delete scheduling object resources in a way that will trigger the   CalDAV server to deliver scheduling message replies to the   "Organizer".     <!ELEMENT schedule-send-reply EMPTY>6.2.4.  CALDAV:schedule-send-freebusy Privilege   The CALDAV:schedule-send-freebusy privilege controls the use of the   POST method to submit scheduling messages that specify the scheduling   method "REQUEST" with a "VFREEBUSY" calendar component.     <!ELEMENT schedule-send-freebusy EMPTY>Daboo & Desruisseaux         Standards Track                   [Page 41]

RFC 6638                    CalDAV Scheduling                  June 20126.3.  Aggregation of Scheduling Privileges   Server implementations MUST aggregate the scheduling privileges as   follows:      DAV:all contains CALDAV:schedule-deliver and CALDAV:schedule-send;      CALDAV:schedule-deliver contains CALDAV:schedule-deliver-invite,      CALDAV:schedule-deliver-reply, and CALDAV:schedule-query-freebusy;      CALDAV:schedule-send contains CALDAV:schedule-send-invite, CALDAV:      schedule-send-reply, and CALDAV:schedule-send-freebusy.   The following diagram illustrates how scheduling privileges are   aggregated according to the above requirements.   [DAV:all] (aggregate)       |       +-- [CALDAV:schedule-deliver] (aggregate)       |      |       |      +-- [CALDAV:schedule-deliver-invite]       |      +-- [CALDAV:schedule-deliver-reply]       |      +-- [CALDAV:schedule-query-freebusy]       |       +-- [CALDAV:schedule-send] (aggregate)              |              +-- [CALDAV:schedule-send-invite]              +-- [CALDAV:schedule-send-reply]              +-- [CALDAV:schedule-send-freebusy]7.  Additional iCalendar Property Parameters   This specification defines additional iCalendar property parameters   to support the CalDAV scheduling extensions.7.1.  Schedule Agent Parameter   Parameter Name:  SCHEDULE-AGENT   Purpose:  To specify the agent expected to deliver scheduling      messages to the corresponding "Organizer" or "Attendee".Daboo & Desruisseaux         Standards Track                   [Page 42]

RFC 6638                    CalDAV Scheduling                  June 2012   Format Definition:  This property parameter is defined by the      following notation:     scheduleagentparam = "SCHEDULE-AGENT" "="                      ("SERVER"      ; The server handles scheduling                     / "CLIENT"      ; The client handles scheduling                     / "NONE"        ; No scheduling                     / x-name        ; Experimental type                     / iana-token)   ; Other IANA-registered type     ;     ; If the parameter is not present, its value defaults to SERVER.     ; "x-name" and "iana-token" are defined inSection 3.1 of     ; [RFC5545].   Description:  This property parameter MAY be specified on "ORGANIZER"      or "ATTENDEE" iCalendar properties.  In the absence of this      parameter, the value "SERVER" MUST be used for the default      behavior.  The value determines whether or not a scheduling      operation on a server will cause a scheduling message to be sent      to the corresponding calendar user identified by the "ORGANIZER"      or "ATTENDEE" property value.  When the value "SERVER" is      specified, or the parameter is absent, then it is the server's      responsibility to send a scheduling message as part of a      scheduling operation.  When the value "CLIENT" is specified, that      indicates that the client is handling scheduling messages with the      calendar user itself.  When "NONE" is specified, no scheduling      messages are being sent to the calendar user.      Servers MUST NOT include this parameter in any scheduling messages      sent as the result of a scheduling operation.      Clients MUST NOT include this parameter in any scheduling messages      that they themselves send.      The parameter value MUST be the same on every "ORGANIZER" property      in a scheduling object resource.      The parameter value MUST be the same on each "ATTENDEE" property      whose values match in a scheduling object resource.      Servers and clients MUST treat x-name and iana-token values they      do not recognize the same way as they would the "NONE" value.   Example:     ORGANIZER;SCHEDULE-AGENT=SERVER:mailto:bernard@example.com     ATTENDEE;SCHEDULE-AGENT=NONE:mailto:cyrus@example.comDaboo & Desruisseaux         Standards Track                   [Page 43]

RFC 6638                    CalDAV Scheduling                  June 20127.2.  Schedule Force Send Parameter   Parameter Name:  SCHEDULE-FORCE-SEND   Purpose:  To force a scheduling message to be sent to the calendar      user specified by the property.   Format Definition:  This property parameter is defined by the      following notation:     scheduleforcesendparam = "SCHEDULE-FORCE-SEND" "="                            ("REQUEST"    ; Force a "REQUEST"                           / "REPLY"      ; Force a "REPLY"                           / iana-token)     ;     ; "iana-token" is defined inSection 3.1 of [RFC5545].  Its value     ; MUST be an IANA-registered iCalendar "METHOD" property value.   Description:  This property parameter MAY be specified on "ATTENDEE"      and "ORGANIZER" properties on which the "SCHEDULE-AGENT" property      parameter is set to the value "SERVER" or is not specified.  This      property parameter is used to force a server to send a scheduling      message to a specific calendar user in situations where the server      would not send a scheduling message otherwise (e.g., when no      change that warrants the delivery of a new scheduling message was      performed on the scheduling object resource).  An "Organizer" MAY      specify this parameter on an "ATTENDEE" property with the value      "REQUEST" to force a "REQUEST" scheduling message to be sent to      this "Attendee".  An "Attendee" MAY specify this parameter on the      "ORGANIZER" with the value "REPLY" to force a "REPLY" scheduling      message to be sent to the "Organizer".      Servers MUST NOT preserve this property parameter in scheduling      object resources, nor include it in any scheduling messages sent      as the result of a scheduling operation.      Clients MUST NOT include this parameter in any scheduling messages      that they themselves send.      Servers MUST set the "SCHEDULE-STATUS" parameter of the "ATTENDEE"      or "ORGANIZER" to 2.3 (i.e., "Success; invalid property parameter      ignored"; seeSection 3.6 of [RFC5546]) when the "SCHEDULE-FORCE-      SEND" parameter is set to an iana-token value they do not      recognize.Daboo & Desruisseaux         Standards Track                   [Page 44]

RFC 6638                    CalDAV Scheduling                  June 2012   Example:     ORGANIZER;SCHEDULE-FORCE-SEND=REPLY:mailto:cyrus@example.com     ATTENDEE;SCHEDULE-FORCE-SEND=REQUEST:mailto:bernard@example.com7.3.  Schedule Status Parameter   Parameter Name:  SCHEDULE-STATUS   Purpose:  To specify the status codes returned from processing of the      most recent scheduling message sent to the corresponding      "Attendee", or received from the corresponding "Organizer".   Format Definition:  This property parameter is defined by the      following notation:     schedulestatusparam = "SCHEDULE-STATUS" "="                         ( statcode                        / DQUOTE statcode *("," statcode) DQUOTE)     ;     ; "statcode" is defined inSection 3.8.8.3 of [RFC5545].  The     ; value is a single "statcode" or a comma-separated list of     ; "statcode" values.   Description:  This property parameter MAY be specified on the      "ATTENDEE" and "ORGANIZER" properties.      Servers MUST only add or change this property parameter on any      "ATTENDEE" properties corresponding to calendar users who were      sent a scheduling message via a scheduling operation.  Clients      SHOULD NOT change or remove this parameter if it was provided by      the server.  In the case where the client is handling the      scheduling, the client MAY add, change, or remove this parameter      to indicate the last scheduling message status it received.      Servers MUST add this parameter to any "ORGANIZER" properties      corresponding to calendar users who were sent a scheduling message      reply by an "Attendee" via a scheduling operation.  Clients SHOULD      NOT change or remove this parameter if it was provided by the      server.  In the case where the client is handling the scheduling,      the client MAY add, change, or remove this parameter to indicate      the last scheduling message status it received.      Servers MUST NOT include this parameter in any scheduling messages      sent as the result of a scheduling operation.      Clients MUST NOT include this parameter in any scheduling messages      that they themselves send.Daboo & Desruisseaux         Standards Track                   [Page 45]

RFC 6638                    CalDAV Scheduling                  June 2012      Values for this property parameter are described inSection 3.2.9.   Example:     ATTENDEE;SCHEDULE-STATUS="2.0":mailto:bernard@example.com     ATTENDEE;SCHEDULE-STATUS="2.0,2.4":mailto:cyrus@example.com8.  Additional Message Header Fields   This specification defines additional HTTP request and response   headers for use with CalDAV.8.1.  Schedule-Reply Request Header     Schedule-Reply = "Schedule-Reply" ":" ("T" | "F")   Example:     Schedule-Reply: F   When an "Attendee" removes a scheduling object resource as perSection 3.2.2.4, and the Schedule-Reply header is set to the value   "T" (true) or is not present, the server MUST send an appropriate   reply scheduling message with the "Attendee's" "PARTSTAT" iCalendar   property parameter value set to "DECLINED" as part of its normal   scheduling operation processing.   When the Schedule-Reply header is set to the value "F" (false), the   server MUST NOT send a scheduling message as part of its normal   scheduling operation processing.   The Schedule-Reply request header is used by a client to indicate to   a server whether or not a scheduling operation ought to occur when an   "Attendee" deletes a scheduling object resource.  In particular, it   controls whether a reply scheduling message is sent to the   "Organizer" as a result of the removal.  There are situations in   which unsolicited scheduling messages need to be silently removed (or   ignored) for security or privacy reasons.  This request header allows   the scheduling object resource to be removed if such a need arises.8.2.  Schedule-Tag Response Header   The Schedule-Tag response header provides the current value of the   CALDAV:schedule-tag property value.  The behavior of this response   header is described inSection 3.2.10.   All scheduling object resources MUST support the Schedule-Tag header.Daboo & Desruisseaux         Standards Track                   [Page 46]

RFC 6638                    CalDAV Scheduling                  June 2012     Schedule-Tag = "Schedule-Tag" ":" opaque-tag     ; "opaque-tag" is defined inSection 3.11 of [RFC2616].   Example:     Schedule-Tag: "12ab34-cd56ef"8.3.  If-Schedule-Tag-Match Request Header   The If-Schedule-Tag-Match request header field is used with a method   to make it conditional.  Clients can set this header to the value   returned in the Schedule-Tag response header, or the CALDAV:schedule-   tag property, of a scheduling object resource previously retrieved   from the server to avoid overwriting "consequential" changes to the   scheduling object resource.   All scheduling object resources MUST support the If-Schedule-Tag-   Match header.     If-Schedule-Tag-Match = "If-Schedule-Tag-Match" ":" opaque-tag     ; "opaque-tag" is defined inSection 3.11 of [RFC2616].   Example:     If-Schedule-Tag-Match: "12ab34-cd56ef"9.  Additional WebDAV Properties   This specification defines the following new WebDAV properties for   use with CalDAV.9.1.  CALDAV:schedule-calendar-transp Property   Name:  schedule-calendar-transp   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Determines whether the calendar object resources in a      calendar collection will affect the owner's busy time information.   Protected:  This property MAY be protected and SHOULD NOT be returned      by a PROPFIND DAV:allprop request (as defined inSection 14.2 of      [RFC4918]).   COPY/MOVE behavior:  This property value SHOULD be kept during a MOVE      operation, and SHOULD be copied and preserved in a COPY.Daboo & Desruisseaux         Standards Track                   [Page 47]

RFC 6638                    CalDAV Scheduling                  June 2012   Description:  This property SHOULD be defined on all calendar      collections.  If present, it contains one of two XML elements that      indicate whether the calendar object resources in the calendar      collection ought to contribute to the owner's busy time.  When the      CALDAV:opaque element is used, all calendar object resources in      the corresponding calendar collection MUST contribute to busy      time, assuming that access privileges and other iCalendar      properties allow it to.  When the CALDAV:transparent XML element      is used, the calendar object resources in the corresponding      calendar collection MUST NOT contribute to busy time.      If this property is not present on a calendar collection, then the      default value CALDAV:opaque MUST be assumed.   Definition:     <!ELEMENT schedule-calendar-transp (opaque | transparent)>     <!ELEMENT opaque EMPTY>     <!-- Affects busy time searches -->     <!ELEMENT transparent EMPTY>     <!-- Invisible to busy time searches -->   Example:     <C:schedule-calendar-transp          xmlns:C="urn:ietf:params:xml:ns:caldav">       <C:opaque/>     </C:schedule-calendar-transp>9.2.  CALDAV:schedule-default-calendar-URL Property   Name:  schedule-default-calendar-URL   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Specifies a default calendar for an "Attendee" where new      scheduling object resources are created.   Protected:  This property MAY be protected in the case where a server      does not support changing the default calendar, or does not      support a default calendar.   COPY/MOVE behavior:  This property is only defined on a scheduling      Inbox collection that cannot be moved or copied.Daboo & Desruisseaux         Standards Track                   [Page 48]

RFC 6638                    CalDAV Scheduling                  June 2012   Description:  This property MAY be defined on a scheduling Inbox      collection.  If present, it contains zero or one DAV:href XML      elements.  When a DAV:href element is present, its value indicates      a URL to a calendar collection that is used as the default      calendar.  When no DAV:href element is present, it indicates that      there is no default calendar.  In the absence of this property,      there is no default calendar.  When there is no default calendar,      the server is free to choose the calendar in which a new      scheduling object resource is created.  SeeSection 4.3.   Definition:     <!ELEMENT schedule-default-calendar-URL (DAV:href?)>   Example:     <C:schedule-default-calendar-URL xmlns:D="DAV:"         xmlns:C="urn:ietf:params:xml:ns:caldav">       <D:href>/home/cyrus/calendars/work/</D:href>     </C:schedule-default-calendar-URL>9.3.  CALDAV:schedule-tag Property   Name:  schedule-tag   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Indicates whether a scheduling object resource has had a      "consequential" change made to it.   Value:  opaque-tag (defined inSection 3.11 of [RFC2616])   Protected:  This property MUST be protected, as only the server can      update the value.   COPY/MOVE behavior:  This property value is determined by the server      and MAY be different from the value on the source resource.   Description:  The CALDAV:schedule-tag property MUST be defined on all      scheduling object resources.  This property is described inSection 3.2.10.   Definition:     <!ELEMENT schedule-tag (#PCDATA)>Daboo & Desruisseaux         Standards Track                   [Page 49]

RFC 6638                    CalDAV Scheduling                  June 2012   Example:     <C:schedule-tag xmlns:C="urn:ietf:params:xml:ns:caldav"     >"12345-67890"</C:schedule-tag>10.  XML Element Definitions10.1.  CALDAV:schedule-response XML Element   Name:  schedule-response   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Contains the set of responses for a POST method request.   Description:  SeeSection 5.   Definition:     <!ELEMENT schedule-response (response*)>10.2.  CALDAV:response XML Element   Name:  response   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  Contains a single response for a POST method request.   Description:  SeeSection 5.   Definition:     <!ELEMENT response (recipient,                         request-status,                         calendar-data?,                         DAV:error?,                         DAV:responsedescription?)>     <!-- CALDAV:calendar-data is defined inSection 9.6 of     RFC 4791 and when used here uses the definition with     content (#PCDATA) only. -->10.3.  CALDAV:recipient XML Element   Name:  recipient   Namespace:  urn:ietf:params:xml:ns:caldavDaboo & Desruisseaux         Standards Track                   [Page 50]

RFC 6638                    CalDAV Scheduling                  June 2012   Purpose:  The calendar user address that the enclosing response for a      POST method request is for.   Description:  SeeSection 5.   Definition:     <!ELEMENT recipient (DAV:href)>10.4.  CALDAV:request-status XML Element   Name:  request-status   Namespace:  urn:ietf:params:xml:ns:caldav   Purpose:  The iTIP "REQUEST-STATUS" property value for this response.   Description:  SeeSection 5.   Definition:     <!ELEMENT request-status (#PCDATA)>11.  Security Considerations   The process of scheduling involves the sending and receiving of   scheduling messages.  As a result, the security problems related to   messaging in general are relevant here.  In particular, the   authenticity of the scheduling messages needs to be verified.   Servers and clients MUST use an HTTP connection protected with   Transport Layer Security (TLS) as defined in [RFC2818] for all   scheduling operations.  Clients MUST use the procedures detailed inSection 6 of [RFC6125] to verify the authenticity of the server.   Servers MUST make use of HTTP authentication [RFC2617] to verify the   authenticity of the calendar user for whom the client is sending   requests.11.1.  Preventing Denial-of-Service Attacks   Servers MUST ensure that clients cannot consume excessive server   resources by carrying out "large" scheduling operations.  In   particular, servers SHOULD enforce CALDAV:max-resource-size, CALDAV:   max-instances, and CALDAV:max-attendees-per-instance preconditions as   applicable for scheduling Inbox and Outbox collections.Daboo & Desruisseaux         Standards Track                   [Page 51]

RFC 6638                    CalDAV Scheduling                  June 201211.2.  Verifying Scheduling Operations   When handling a scheduling operation:   1.  Servers MUST verify that the principal associated with the DAV:       owner of the calendar collection in which a scheduling object       resource is being manipulated contains a CALDAV:schedule-outbox-       URL property value.   2.  Servers MUST verify that the currently authenticated user has the       CALDAV:schedule-send privilege, or a sub-privilege aggregated       under this privilege, on the scheduling Outbox collection of the       DAV:owner of the calendar collection in which a scheduling object       resource is being manipulated.   3.  Servers MUST only deliver scheduling messages to recipients when       the CALDAV:schedule-deliver privilege, or a sub-privilege       aggregated under this privilege, is granted on the recipient's       scheduling Inbox collection for the principal associated with the       DAV:owner of the calendar collection in which a scheduling object       resource is being manipulated.   4.  To prevent impersonation of calendar users, the server MUST       verify that the "ORGANIZER" property in an organizer scheduling       object resource matches one of the calendar user addresses of the       DAV:owner of the calendar collection in which the resource is       stored.   5.  To prevent spoofing of an existing scheduling object resource,       servers MUST verify that the "UID" iCalendar property value in a       new scheduling object resource does not match that of an existing       scheduling object resource with a different "ORGANIZER" property       value.11.3.  Verifying Busy Time Information Requests   When handling a POST request on a scheduling Outbox collection:   1.  Servers MUST verify that the principal associated with the       calendar user address specified in the "ORGANIZER" property of       the scheduling message data in the request contains a CALDAV:       schedule-outbox-URL property value that matches the scheduling       Outbox collection targeted by the request.   2.  Servers MUST verify that the currently authenticated user has the       CALDAV:schedule-send privilege, or a sub-privilege aggregated       under this privilege, on the scheduling Outbox collection       targeted by the request.Daboo & Desruisseaux         Standards Track                   [Page 52]

RFC 6638                    CalDAV Scheduling                  June 2012   3.  Servers MUST only return valid freebusy information for       recipients when the CALDAV:schedule-deliver privilege, or a       sub-privilege aggregated under this privilege, is granted on the       recipient's scheduling Inbox collection for the principal       associated with the DAV:owner of the scheduling Outbox collection       targeted by the request.11.4.  Privacy Issues   This specification only defines how calendar users on the same server   are able to schedule with each other -- unauthenticated users have no   way to carry out scheduling operations.  Access control privileges   (as perSection 6) can control which of those users can schedule with   others.  Calendar users not wishing to expose their calendar   information to other users can do so by denying privileges to   specific users, or all users, for all scheduling operations, or   perhaps only freebusy.   "Attendees" can also use the Schedule-Reply request header   (Section 8.1) with the value set to "F" to prevent notification to an   "Organizer" that a scheduling object resource was deleted.  This   allows "Attendees" to remove unwanted scheduling messages without any   response to the "Organizer".   Servers MUST NOT expose any private iCalendar data, or WebDAV   resource state information (URLs, WebDAV properties, etc.) for one   calendar user to another via scheduling messages or error responses   to scheduling operations.  In particular, as perSection 8.1 of   [RFC4918], authorization errors MUST take preference over other   errors.11.5.  Mitigation of iTIP ThreatsSection 6.1 of iTIP [RFC5546] defines a set of potential threats in a   scheduling system, andSection 6.2 of [RFC5546] defines   recommendations on how those can be addressed in protocols using   iTIP.  This specification addresses the iTIP threats in the following   manner:   Spoofing the "Organizer":  Addressed by item 4 inSection 11.2.   Spoofing the "Attendee":  Addressed bySection 3.2.2.1 and item 2 inSection 11.2.   Unauthorized Replacement of the "Organizer":  Addressed by item 5 inSection 11.2.   Eavesdropping and Data Integrity:  Addressed by requiring TLS.Daboo & Desruisseaux         Standards Track                   [Page 53]

RFC 6638                    CalDAV Scheduling                  June 2012   Flooding a Calendar:  Addressed by requirements inSection 11.1.   Unauthorized REFRESH Requests:  This specification does not support      the REFRESH method.12.  IANA Considerations12.1.  Message Header Field Registrations   The message header fields below have been added to the Permanent   Message Header Field Registry (see [RFC3864]).12.1.1.  Schedule-Reply   Header field name: Schedule-Reply   Applicable protocol: http   Status: standard   Author/Change controller: IETF   Specification document(s): this specification (Section 8.1)   Related information: none12.1.2.  Schedule-Tag   Header field name: Schedule-Tag   Applicable protocol: http   Status: standard   Author/Change controller: IETF   Specification document(s): this specification (Section 8.2)   Related information: none12.1.3.  If-Schedule-Tag-Match   Header field name: If-Schedule-Tag-Match   Applicable protocol: http   Status: standardDaboo & Desruisseaux         Standards Track                   [Page 54]

RFC 6638                    CalDAV Scheduling                  June 2012   Author/Change controller: IETF   Specification document(s): this specification (Section 8.3)   Related information: none12.2.  iCalendar Property Parameter Registrations   The following iCalendar property parameter names have been added to   the iCalendar Parameters Registry defined inSection 8.3.3 of   [RFC5545].         +---------------------+---------+-----------------------+         | Parameter           | Status  | Reference             |         +---------------------+---------+-----------------------+         | SCHEDULE-AGENT      | Current |RFC 6638, Section 7.1 |         |                     |         |                       |         | SCHEDULE-STATUS     | Current |RFC 6638, Section 7.3 |         |                     |         |                       |         | SCHEDULE-FORCE-SEND | Current |RFC 6638, Section 7.2 |         +---------------------+---------+-----------------------+12.3.  iCalendar REQUEST-STATUS Value Registrations   The following iCalendar "REQUEST-STATUS" values have been added to   the iCalendar REQUEST-STATUS Value Registry defined inSection 7.3 of   [RFC5546].           +-------------+---------+---------------------------+           | Status Code | Status  | Reference                 |           +-------------+---------+---------------------------+           | 1.0         | Current |RFC 6638, Section 3.2.9.1 |           |             |         |                           |           | 1.1         | Current |RFC 6638, Section 3.2.9.2 |           |             |         |                           |           | 1.2         | Current |RFC 6638, Section 3.2.9.3 |           +-------------+---------+---------------------------+12.4.  Additional iCalendar Elements Registries   Per this specification, two new IANA registries for iCalendar   elements have been added.  Additional codes MAY be used, provided the   process described inSection 8.2.1 of [RFC5545] is used to register   them.Daboo & Desruisseaux         Standards Track                   [Page 55]

RFC 6638                    CalDAV Scheduling                  June 201212.4.1.  Schedule Agent Values Registry   The following table has been used to initialize the Schedule Agent   Values Registry.           +----------------+---------+-----------------------+           | Schedule Agent | Status  | Reference             |           +----------------+---------+-----------------------+           | SERVER         | Current |RFC 6638, Section 7.1 |           |                |         |                       |           | CLIENT         | Current |RFC 6638, Section 7.1 |           |                |         |                       |           | NONE           | Current |RFC 6638, Section 7.1 |           +----------------+---------+-----------------------+12.4.2.  Schedule Force Send Values Registry   The following table has been used to initialize the Schedule Force   Send Values Registry.         +---------------------+---------+-----------------------+         | Schedule Force Send | Status  | Reference             |         +---------------------+---------+-----------------------+         | REQUEST             | Current |RFC 6638, Section 7.2 |         |                     |         |                       |         | REPLY               | Current |RFC 6638, Section 7.2 |         +---------------------+---------+-----------------------+13.  Acknowledgements   The authors would like to thank the following individuals for   contributing their ideas and support for writing this specification:   Mike Douglass, Lisa Dusseault, Red Dutta, Jacob Farkas, Jeffrey   Harris, Helge Hess, Eliot Lear, Andrew McMillan, Alexey Melnikov,   Arnaud Quillaud, Julian F. Reschke, Wilfredo Sanchez Vega, and Simon   Vaillancourt.   The authors would also like to thank the Calendaring and Scheduling   Consortium for advice with this specification, and for organizing   interoperability testing events to help refine it.Daboo & Desruisseaux         Standards Track                   [Page 56]

RFC 6638                    CalDAV Scheduling                  June 201214.  References14.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [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.   [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,              Leach, P., Luotonen, A., and L. Stewart, "HTTP              Authentication: Basic and Digest Access Authentication",RFC 2617, June 1999.   [RFC2818]  Rescorla, E., "HTTP Over TLS",RFC 2818, May 2000.   [RFC3744]  Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web              Distributed Authoring and Versioning (WebDAV)              Access Control Protocol",RFC 3744, May 2004.   [RFC3864]  Klyne, G., Nottingham, M., and J. Mogul, "Registration              Procedures for Message Header Fields",BCP 90,RFC 3864,              September 2004.   [RFC4791]  Daboo, C., Desruisseaux, B., and L. Dusseault,              "Calendaring Extensions to WebDAV (CalDAV)",RFC 4791,              March 2007.   [RFC4918]  Dusseault, L., Ed., "HTTP Extensions for Web Distributed              Authoring and Versioning (WebDAV)",RFC 4918, June 2007.   [RFC5234]  Crocker, D., Ed., and P. Overell, "Augmented BNF for              Syntax Specifications: ABNF", STD 68,RFC 5234,              January 2008.   [RFC5545]  Desruisseaux, B., Ed., "Internet Calendaring and              Scheduling Core Object Specification (iCalendar)",RFC 5545, September 2009.   [RFC5546]  Daboo, C., Ed., "iCalendar Transport-Independent              Interoperability Protocol (iTIP)",RFC 5546,              December 2009.Daboo & Desruisseaux         Standards Track                   [Page 57]

RFC 6638                    CalDAV Scheduling                  June 2012   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and              Verification of Domain-Based Application Service Identity              within Internet Public Key Infrastructure Using X.509              (PKIX) Certificates in the Context of Transport Layer              Security (TLS)",RFC 6125, March 2011.   [W3C.REC-xml-20081126]              Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E.,              and F. Yergeau, "Extensible Markup Language (XML) 1.0              (Fifth Edition)", World Wide Web Consortium              Recommendation REC-xml-20081126, November 2008,              <http://www.w3.org/TR/2008/REC-xml-20081126>.14.2.  Informative References   [RFC6047]  Melnikov, A., Ed., "iCalendar Message-Based              Interoperability Protocol (iMIP)",RFC 6047,              December 2010.Daboo & Desruisseaux         Standards Track                   [Page 58]

RFC 6638                    CalDAV Scheduling                  June 2012Appendix A.  Scheduling Privileges SummaryA.1.  Scheduling Inbox Privileges   The following tables specify which scheduling privileges grant the   right to a calendar user to deliver a scheduling message to the   scheduling Inbox collection of another calendar user.  The   appropriate behavior depends on the calendar component type as well   as the scheduling "METHOD" specified in the scheduling message.                                 +--------------------------------+                                 |  METHOD for VEVENT and VTODO   |   +-----------------------------+---------+-------+-----+--------+   | Scheduling Inbox Privilege  | REQUEST | REPLY | ADD | CANCEL |   +-----------------------------+---------+-------+-----+--------+   | schedule-deliver            |    *    |   *   |  *  |   *    |   |   schedule-deliver-invite   |    *    |       |  *  |   *    |   |   schedule-deliver-reply    |         |   *   |     |        |   |   schedule-query-freebusy   |         |       |     |        |   +-----------------------------+---------+-------+-----+--------+                                 +----------------------+                                 | METHOD for VFREEBUSY |   +-----------------------------+----------------------+   | Scheduling Inbox Privilege  |       REQUEST        |   +-----------------------------+----------------------+   | schedule-deliver            |          *           |   |   schedule-deliver-invite   |                      |   |   schedule-deliver-reply    |                      |   |   schedule-query-freebusy   |          *           |   +-----------------------------+----------------------+Daboo & Desruisseaux         Standards Track                   [Page 59]

RFC 6638                    CalDAV Scheduling                  June 2012A.2.  Scheduling Outbox Privileges   The following tables specify which scheduling privileges grant the   right to a calendar user to perform busy time information requests   and to submit scheduling messages to other calendar users as the   result of a scheduling operation.  The appropriate behavior depends   on the calendar component type as well as the scheduling "METHOD"   specified in the scheduling message.                                 +--------------------------------+                                 |  METHOD for VEVENT and VTODO   |   +-----------------------------+---------+-------+-----+--------+   | Scheduling Outbox Privilege | REQUEST | REPLY | ADD | CANCEL |   +-----------------------------+---------+-------+-----+--------+   | schedule-send               |    *    |   *   |  *  |   *    |   |   schedule-send-invite      |    *    |       |  *  |   *    |   |   schedule-send-reply       |         |   *   |     |        |   |   schedule-send-freebusy    |         |       |     |        |   +-----------------------------+---------+-------+-----+--------+                                 +----------------------+                                 | METHOD for VFREEBUSY |   +-----------------------------+----------------------+   | Scheduling Outbox Privilege |       REQUEST        |   +-----------------------------+----------------------+   | schedule-send               |          *           |   |   schedule-send-invite      |                      |   |   schedule-send-reply       |                      |   |   schedule-send-freebusy    |          *           |   +-----------------------------+----------------------+Appendix B.  Example Scheduling Operations   This section describes some example scheduling operations that give a   general idea of how scheduling is carried out between CalDAV clients   and servers from the perspective of meeting "Organizers" and   "Attendees".   The server is assumed to be hosted in the "example.com" domain, and   users whose email addresses are at the "example.com" domain are   assumed to be hosted by the server.  In addition, the email addresses   in the "example.net" domain are also valid email addresses for   calendar users hosted by the server.  Calendar users with an email   address at the "example.org" domain are assumed to not be hosted by   the server.Daboo & Desruisseaux         Standards Track                   [Page 60]

RFC 6638                    CalDAV Scheduling                  June 2012   In the following examples, the requests and responses are incomplete   and are only for illustrative purposes.  In particular, HTTP   authentication headers and behaviors are not shown, even though they   are required in normal operation.B.1.  Example: "Organizer" Inviting Multiple "Attendees"   In the following example, Cyrus invites Wilfredo, Bernard, and Mike   to a single instance event by simply creating a new scheduling object   resource in one of his calendar collections by using the PUT method.   >> Request <<   PUT /home/cyrus/calendars/work/9263504FD3AD.ics HTTP/1.1   Host: cal.example.com   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   If-None-Match: *   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T185254Z   DTSTART:20090602T160000Z   DTEND:20090602T170000Z   TRANSP:OPAQUE   SUMMARY:Lunch   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega";CUTYPE=INDIVIDUAL;PARTSTAT    =NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:wilfredo@    example.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@ex    ample.net   ATTENDEE;CN="Mike Douglass";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-A    CTION;RSVP=TRUE:mailto:mike@example.org   END:VEVENT   END:VCALENDAR   >> Response <<   HTTP/1.1 201 Created   Content-Length: 0Daboo & Desruisseaux         Standards Track                   [Page 61]

RFC 6638                    CalDAV Scheduling                  June 2012   Date: Tue, 02 Jun 2009 18:52:54 GMT   Last-Modified: Tue, 02 Jun 2009 18:52:54 GMT   ETag: "d85561cfe74a4e785eb4639451b434fb"   Schedule-Tag: "488177c8-2ea7-4176-a6cb-fab8cfccdea2"   Once the event creation has been completed, Cyrus's client will   retrieve the event back from the server to get the schedule status of   each "Attendee", as well as record the Schedule-Tag value for future   use.  In this example, the server reports that a scheduling message   was delivered to Wilfredo, a scheduling message is still pending for   Bernard, and the server was unable to deliver a scheduling message to   Mike.   >> Request <<   GET /home/cyrus/calendars/work/9263504FD3AD.ics HTTP/1.1   Host: cal.example.com   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 18:52:58 GMT   Last-Modified: Tue, 02 Jun 2009 18:52:58 GMT   ETag: "eb897deabc8939589da116714bc99265"   Schedule-Tag: "488177c8-2ea7-4176-a6cb-fab8cfccdea2"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Server//EN   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T185300Z   DTSTART:20090602T160000Z   DTEND:20090602T170000Z   TRANSP:OPAQUE   SUMMARY:Lunch   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega";CUTYPE=INDIVIDUAL;PARTSTAT    =NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE;SCHEDULE-STATUS=    1.2:mailto:wilfredo@e    xample.comDaboo & Desruisseaux         Standards Track                   [Page 62]

RFC 6638                    CalDAV Scheduling                  June 2012   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE;SCHEDULE-STATUS=    1.0:mailto:bernard@example.net   ATTENDEE;CN="Mike Douglass";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-A    CTION;RSVP=TRUE;SCHEDULE-STATUS=3.7:mailto:mike@example.org   END:VEVENT   END:VCALENDARB.2.  Example: "Attendee" Receiving an Invitation   In the following example, Wilfredo's client retrieves and deletes the   new scheduling message that appeared in his scheduling Inbox   collection after the server automatically processed it and created a   new scheduling object resource in his default calendar collection.   >> Request <<   GET /home/wilfredo/calendars/inbox/27d93fc0a58c.ics HTTP/1.1   Host: cal.example.com   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 18:59:58 GMT   Last-Modified: Tue, 02 Jun 2009 18:59:58 GMT   ETag: "da116714bc9926c89395895eb897deab"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Server//EN   METHOD:REQUEST   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T185254Z   DTSTART:20090602T160000Z   DTEND:20090602T170000Z   TRANSP:OPAQUE   SUMMARY:Lunch   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega";CUTYPE=INDIVIDUAL;PARTSTAT    =NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:wilfredo@    example.comDaboo & Desruisseaux         Standards Track                   [Page 63]

RFC 6638                    CalDAV Scheduling                  June 2012   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@ex    ample.net   ATTENDEE;CN="Mike Douglass";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-A    CTION;RSVP=TRUE:mailto:mike@example.org   END:VEVENT   END:VCALENDAR   >> Request <<   DELETE /home/wilfredo/calendars/inbox/27d93fc0a58c.ics HTTP/1.1   Host: cal.example.com   >> Response <<   HTTP/1.1 204 No Content   Date: Tue, 02 Jun 2009 20:40:36 GMTB.3.  Example: "Attendee" Replying to an Invitation   In the following example, Wilfredo accepts Cyrus's invitation and   sets an alarm reminder on the event.  It uses the If-Schedule-Tag-   Match precondition behavior to ensure it does not overwrite any   significant changes from the "Organizer" that might have occurred   after it retrieved the initial resource data.   >> Request <<   PUT /home/wilfredo/calendars/work/BB64861C2228.ics HTTP/1.1   Host: cal.example.com   If-Schedule-Tag-Match: "e78f23ed-0188-4bab-938d-2aeb3324c7e8"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T185254Z   DTSTART:20090602T160000Z   DTEND:20090602T170000Z   TRANSP:OPAQUE   SUMMARY:Lunch   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.comDaboo & Desruisseaux         Standards Track                   [Page 64]

RFC 6638                    CalDAV Scheduling                  June 2012   ATTENDEE;CN="Wilfredo Sanchez Vega";CUTYPE=INDIVIDUAL;PARTSTAT    =ACCEPTED;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:wilfredo@exam    ple.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@ex    ample.net   ATTENDEE;CN="Mike Douglass";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-A    CTION;RSVP=TRUE:mailto:mike@example.org   BEGIN:VALARM   TRIGGER:-PT15M   ACTION:DISPLAY   DESCRIPTION:Reminder   END:VALARM   END:VEVENT   END:VCALENDAR   >> Response <<   HTTP/1.1 200 OK   Content-Length: 0   Date: Tue, 02 Jun 2009 18:57:54 GMT   Last-Modified: Tue, 02 Jun 2009 18:57:54 GMT   ETag: "eb4639451b434fbd85561cfe74a4e785"   Schedule-Tag: "8893ee45-eb9d-428f-b53c-c777daf19e41"   Once the event modification has been completed, Wilfredo's client   will retrieve the event back from the server to get the schedule   status of the "Organizer".   >> Request <<   GET /home/wilfredo/calendars/work/BB64861C2228.ics HTTP/1.1   Host: cal.example.com   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 19:03:03 GMT   Last-Modified: Tue, 02 Jun 2009 19:02:21 GMT   ETag: "5eb897deabda116714bc9926c8939589"   Schedule-Tag: "8893ee45-eb9d-428f-b53c-c777daf19e41"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxxDaboo & Desruisseaux         Standards Track                   [Page 65]

RFC 6638                    CalDAV Scheduling                  June 2012   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T190221Z   DTSTART:20090602T160000Z   DTEND:20090602T170000Z   TRANSP:OPAQUE   SUMMARY:Lunch   ORGANIZER;CN="Cyrus Daboo";SCHEDULE-STATUS=1.2:mailto:cyrus@ex    ample.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega";CUTYPE=INDIVIDUAL;PARTSTAT    =ACCEPTED;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:wilfredo@exam    ple.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@ex    ample.net   ATTENDEE;CN="Mike Douglass";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-A    CTION;RSVP=TRUE:mailto:mike@example.org   BEGIN:VALARM   TRIGGER:-PT15M   ACTION:DISPLAY   DESCRIPTION:Reminder   END:VALARM   END:VEVENT   END:VCALENDARB.4.  Example: "Organizer" Receiving a Reply to an Invitation   On reception of Wilfredo's reply, Cyrus's server will automatically   update Cyrus's scheduling object resource, make Wilfredo's scheduling   message available in Cyrus's scheduling Inbox collection, and deliver   an updated scheduling message to Bernard to share Wilfredo's updated   participation status.  In this example, Cyrus's client retrieves and   deletes this scheduling message in his scheduling Inbox collection.   >> Request <<   GET /home/cyrus/calendars/inbox/c0a58c27d93f.ics HTTP/1.1   Host: cal.example.comDaboo & Desruisseaux         Standards Track                   [Page 66]

RFC 6638                    CalDAV Scheduling                  June 2012   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 19:05:02 GMT   Last-Modified: Tue, 02 Jun 2009 19:04:20 GMT   ETag: "9265eb897deabc8939589da116714bc9"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Server//EN   METHOD:REPLY   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T185754Z   DTSTART:20090602T160000Z   DTEND:20090602T170000Z   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega";PARTSTAT=ACCEPTED:mailto:w    ilfredo@example.com   REQUEST-STATUS:2.0;Success   END:VEVENT   END:VCALENDAR   >> Request <<   DELETE /home/cyrus/calendars/inbox/c0a58c27d93f.ics HTTP/1.1   Host: cal.example.com   >> Response <<   HTTP/1.1 204 No Content   Date: Tue, 02 Jun 2009 19:05:05 GMT   Cyrus's client then retrieves the event back from the server with   Wilfredo's updated participation status.   >> Request <<   GET /home/cyrus/calendars/work/9263504FD3AD.ics HTTP/1.1   Host: cal.example.comDaboo & Desruisseaux         Standards Track                   [Page 67]

RFC 6638                    CalDAV Scheduling                  June 2012   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 19:05:02 GMT   Last-Modified: Tue, 02 Jun 2009 19:04:20 GMT   ETag: "eb897deabc8939589da116714bc99265"   Schedule-Tag: "132cab27-1fe3-67ab-de13-abd348d1dee3"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Server//EN   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T190420Z   DTSTART:20090602T160000Z   DTEND:20090602T170000Z   TRANSP:OPAQUE   SUMMARY:Lunch   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega";CUTYPE=INDIVIDUAL;PARTSTAT    =ACCEPTED;ROLE=REQ-PARTICIPANT;RSVP=TRUE;SCHEDULE-STATUS=2.0:    mailto:wilfredo@example.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE;SCHEDULE-STATUS=1    .0:mailto:bernard@example.net   ATTENDEE;CN="Mike Douglass";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-A    CTION;RSVP=TRUE;SCHEDULE-STATUS=3.7:mailto:mike@example.org   END:VEVENT   END:VCALENDARDaboo & Desruisseaux         Standards Track                   [Page 68]

RFC 6638                    CalDAV Scheduling                  June 2012B.5.  Example: "Organizer" Requesting Busy Time Information   In this example, Cyrus requests the busy time information of   Wilfredo, Bernard, and Mike.   >> Request <<   POST /home/cyrus/calendars/outbox/ HTTP/1.1   Host: cal.example.com   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   METHOD:REQUEST   BEGIN:VFREEBUSY   UID:4FD3AD926350   DTSTAMP:20090602T190420Z   DTSTART:20090602T000000Z   DTEND:20090604T000000Z   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega":mailto:wilfredo@example.com   ATTENDEE;CN="Bernard Desruisseaux":mailto:bernard@example.net   ATTENDEE;CN="Mike Douglass":mailto:mike@example.org   END:VFREEBUSY   END:VCALENDAR   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 20:07:34 GMT   Content-Type: application/xml; charset="utf-8"   Content-Length: xxxx   <?xml version="1.0" encoding="utf-8" ?>   <C:schedule-response xmlns:D="DAV:"          xmlns:C="urn:ietf:params:xml:ns:caldav">   <C:response>   <C:recipient>   <D:href>mailto:wilfredo@example.com</D:href>   </C:recipient>   <C:request-status>2.0;Success</C:request-status>   <C:calendar-data>BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Server//EN   METHOD:REPLY   BEGIN:VFREEBUSYDaboo & Desruisseaux         Standards Track                   [Page 69]

RFC 6638                    CalDAV Scheduling                  June 2012   UID:4FD3AD926350   DTSTAMP:20090602T200733Z   DTSTART:20090602T000000Z   DTEND:20090604T000000Z   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega":mailto:wilfredo@example.com   FREEBUSY;FBTYPE=BUSY:20090602T110000Z/20090602T120000Z   FREEBUSY;FBTYPE=BUSY:20090603T170000Z/20090603T180000Z   END:VFREEBUSY   END:VCALENDAR   </C:calendar-data>   </C:response>   <C:response>   <C:recipient>   <D:href>mailto:bernard@example.net</D:href>   </C:recipient>   <C:request-status>2.0;Success</C:request-status>   <C:calendar-data>BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Server//EN   METHOD:REPLY   BEGIN:VFREEBUSY   UID:4FD3AD926350   DTSTAMP:20090602T200733Z   DTSTART:20090602T000000Z   DTEND:20090604T000000Z   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Bernard Desruisseaux":mailto:bernard@example.net   FREEBUSY;FBTYPE=BUSY:20090602T150000Z/20090602T160000Z   FREEBUSY;FBTYPE=BUSY:20090603T090000Z/20090603T100000Z   FREEBUSY;FBTYPE=BUSY:20090603T180000Z/20090603T190000Z   END:VFREEBUSY   END:VCALENDAR   </C:calendar-data>   </C:response>   <C:response>   <C:recipient>   <D:href>mailto:mike@example.org</D:href>   </C:recipient>   <C:request-status>3.7;Invalid calendar user</C:request-status>   </C:response>   </C:schedule-response>Daboo & Desruisseaux         Standards Track                   [Page 70]

RFC 6638                    CalDAV Scheduling                  June 2012B.6.  Example: User Attempting to Invite "Attendee" on Behalf of      "Organizer"   In the following example, Cyrus attempts to create, on behalf of   Wilfredo, an event with Bernard specified as an "Attendee".  The   request fails, since Wilfredo didn't grant Cyrus the right to invite   other calendar users on his behalf.   >> Request <<   PUT /home/wilfredo/calendars/work/def456.ics HTTP/1.1   Host: cal.example.com   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   If-None-Match: *   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   BEGIN:VEVENT   UID:3504F926D3AD   SEQUENCE:0   DTSTAMP:20090602T190221Z   DTSTART:20090602T230000Z   DTEND:20090603T000000Z   TRANSP:OPAQUE   SUMMARY:Dinner   ORGANIZER;CN="Wilfredo Sanchez Vega":mailto:wilfredo@example.com   ATTENDEE;CN="Wilfredo Sanchez Vega";CUTYPE=INDIVIDUAL;PARTSTAT=A    CCEPTED:mailto:wilfredo@example.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=NE    EDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@exampl    e.net   END:VEVENT   END:VCALENDARDaboo & Desruisseaux         Standards Track                   [Page 71]

RFC 6638                    CalDAV Scheduling                  June 2012   >> Response <<   HTTP/1.1 403 Forbidden   Content-Type: application/xml; charset="utf-8"   Content-Length: xxxx   <?xml version="1.0" encoding="utf-8" ?>   <D:error xmlns:D="DAV:" xmlns:C="urn:ietf:params:xml:ns:caldav">     <D:need-privileges>       <D:resource>         <D:href>/home/wilfredo/calendars/outbox/</D:href>         <D:privilege><C:schedule-send-invite/></D:privilege>       </D:resource>     </D:need-privileges>   </D:error>B.7.  Example: "Attendee" Declining an Instance of a Recurring Event   In the following example, Bernard declines the second recurrence   instance of a daily recurring event he's been invited to by Cyrus.   >> Request <<   PUT /home/bernard/calendars/work/4FD3AD926350.ics HTTP/1.1   Host: cal.example.com   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   If-Schedule-Tag-Match: "7775FB30-7534-489E-A79A-0EA147B933EB"   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   BEGIN:VTIMEZONE   TZID:America/Montreal   BEGIN:STANDARD   DTSTART:20071104T020000   RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU   TZNAME:EST   TZOFFSETFROM:-0400   TZOFFSETTO:-0500   END:STANDARD   BEGIN:DAYLIGHT   DTSTART:20070311T020000   RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU   TZNAME:EDT   TZOFFSETFROM:-0500   TZOFFSETTO:-0400   END:DAYLIGHTDaboo & Desruisseaux         Standards Track                   [Page 72]

RFC 6638                    CalDAV Scheduling                  June 2012   END:VTIMEZONE   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T185254Z   DTSTART;TZID=America/Montreal:20090601T150000   DTEND;TZID=America/Montreal:20090601T160000   RRULE:FREQ=DAILY;INTERVAL=1;COUNT=5   TRANSP:OPAQUE   SUMMARY:Review Internet-Draft   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    ACCEPTED;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@exampl    e.net   END:VEVENT   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090603T183823Z   RECURRENCE-ID;TZID=America/Montreal:20090602T150000   DTSTART;TZID=America/Montreal:20090602T150000   DTEND;TZID=America/Montreal:20090602T160000   TRANSP:TRANSPARENT   SUMMARY:Review Internet-Draft   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    DECLINED;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@exampl    e.net   END:VEVENT   END:VCALENDAR   >> Response <<   HTTP/1.1 200 OK   Content-Length: 0   Date: Tue, 02 Jun 2009 18:52:54 GMT   Last-Modified: Tue, 02 Jun 2009 18:52:54 GMT   ETag: "d85561cfe74a4e785eb4639451b434fb"   Schedule-Tag: "488177c8-2ea7-4176-a6cb-fab8cfccdea2"Daboo & Desruisseaux         Standards Track                   [Page 73]

RFC 6638                    CalDAV Scheduling                  June 2012   Bernard's participation status update will cause his server to   deliver a scheduling message to Cyrus.  Cyrus's client will find the   following reply message from Bernard in Cyrus's scheduling Inbox   collection:   >> Request <<   GET /home/cyrus/calendars/inbox/9263504FD3AD.ics HTTP/1.1   Host: cal.example.com   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 18:52:58 GMT   Last-Modified: Tue, 02 Jun 2009 18:52:58 GMT   ETag: "eb897deabc8939589da116714bc99265"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   METHOD:REPLY   BEGIN:VTIMEZONE   TZID:America/Montreal   BEGIN:STANDARD   DTSTART:20071104T020000   RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU   TZNAME:EST   TZOFFSETFROM:-0400   TZOFFSETTO:-0500   END:STANDARD   BEGIN:DAYLIGHT   DTSTART:20070311T020000   RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU   TZNAME:EDT   TZOFFSETFROM:-0500   TZOFFSETTO:-0400   END:DAYLIGHT   END:VTIMEZONE   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090603T183823Z   RECURRENCE-ID;TZID=America/Montreal:20090602T150000   DTSTART;TZID=America/Montreal:20090602T150000   DTEND;TZID=America/Montreal:20090602T160000   SUMMARY:Review Internet-DraftDaboo & Desruisseaux         Standards Track                   [Page 74]

RFC 6638                    CalDAV Scheduling                  June 2012   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Bernard Desruisseaux";PARTSTAT=DECLINED:    mailto:bernard@example.net   REQUEST-STATUS:2.0;Success   END:VEVENT   END:VCALENDARB.8.  Example: "Attendee" Removing an Instance of a Recurring Event   In the following example, Bernard removes from his calendar the third   recurrence instance of a daily recurring event he's been invited to   by Cyrus.  This is accomplished by the addition of an "EXDATE"   property to the scheduling object resource stored by Bernard.   >> Request <<   PUT /home/bernard/calendars/work/4FD3AD926350.ics HTTP/1.1   Host: cal.example.com   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxx   If-Schedule-Tag-Match: "488177c8-2ea7-4176-a6cb-fab8cfccdea2"   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   BEGIN:VTIMEZONE   TZID:America/Montreal   BEGIN:STANDARD   DTSTART:20071104T020000   RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU   TZNAME:EST   TZOFFSETFROM:-0400   TZOFFSETTO:-0500   END:STANDARD   BEGIN:DAYLIGHT   DTSTART:20070311T020000   RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU   TZNAME:EDT   TZOFFSETFROM:-0500   TZOFFSETTO:-0400   END:DAYLIGHT   END:VTIMEZONE   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090602T185254Z   DTSTART;TZID=America/Montreal:20090601T150000   DTEND;TZID=America/Montreal:20090601T160000Daboo & Desruisseaux         Standards Track                   [Page 75]

RFC 6638                    CalDAV Scheduling                  June 2012   RRULE:FREQ=DAILY;INTERVAL=1;COUNT=5   EXDATE;TZID=America/Montreal:20090603T150000   TRANSP:OPAQUE   SUMMARY:Review Internet-Draft   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    ACCEPTED;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@exampl    e.net   END:VEVENT   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090603T183823Z   RECURRENCE-ID;TZID=America/Montreal:20090602T150000   DTSTART;TZID=America/Montreal:20090602T150000   DTEND;TZID=America/Montreal:20090602T160000   TRANSP:TRANSPARENT   SUMMARY:Review Internet-Draft   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Cyrus Daboo";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:    mailto:cyrus@example.com   ATTENDEE;CN="Bernard Desruisseaux";CUTYPE=INDIVIDUAL;PARTSTAT=    DECLINED;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:bernard@exampl    e.net   END:VEVENT   END:VCALENDAR   Bernard's deletion of a recurrence instance will cause his server to   deliver a scheduling message to Cyrus.  Cyrus's client will find the   following reply message from Bernard in Cyrus's scheduling Inbox   collection:   >> Request <<   GET /home/cyrus/calendars/inbox/6504923FD3AD.ics HTTP/1.1   Host: cal.example.com   >> Response <<   HTTP/1.1 200 OK   Date: Tue, 02 Jun 2009 18:52:58 GMT   Last-Modified: Tue, 02 Jun 2009 18:52:58 GMT   ETag: "eb897deabc8939589da116714bc99265"   Content-Type: text/calendar; charset="utf-8"   Content-Length: xxxxDaboo & Desruisseaux         Standards Track                   [Page 76]

RFC 6638                    CalDAV Scheduling                  June 2012   BEGIN:VCALENDAR   VERSION:2.0   PRODID:-//Example Corp.//CalDAV Client//EN   METHOD:REPLY   BEGIN:VTIMEZONE   TZID:America/Montreal   BEGIN:STANDARD   DTSTART:20071104T020000   RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU   TZNAME:EST   TZOFFSETFROM:-0400   TZOFFSETTO:-0500   END:STANDARD   BEGIN:DAYLIGHT   DTSTART:20070311T020000   RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU   TZNAME:EDT   TZOFFSETFROM:-0500   TZOFFSETTO:-0400   END:DAYLIGHT   END:VTIMEZONE   BEGIN:VEVENT   UID:9263504FD3AD   SEQUENCE:0   DTSTAMP:20090603T183823Z   RECURRENCE-ID;TZID=America/Montreal:20090603T150000   DTSTART;TZID=America/Montreal:20090603T150000   DTEND;TZID=America/Montreal:20090603T160000   SUMMARY:Review Internet-Draft   ORGANIZER;CN="Cyrus Daboo":mailto:cyrus@example.com   ATTENDEE;CN="Bernard Desruisseaux";PARTSTAT=DECLINED:    mailto:bernard@example.net   REQUEST-STATUS:2.0;Success   END:VEVENT   END:VCALENDARDaboo & Desruisseaux         Standards Track                   [Page 77]

RFC 6638                    CalDAV Scheduling                  June 2012Authors' Addresses   Cyrus Daboo   Apple Inc.   1 Infinite Loop   Cupertino, CA  95014   USA   EMail: cyrus@daboo.name   URI:http://www.apple.com/   Bernard Desruisseaux   Oracle Corporation   600 Blvd. de Maisonneuve West   Suite 1900   Montreal, QC  H3A 3J2   CANADA   EMail: bernard.desruisseaux@oracle.com   URI:http://www.oracle.com/Daboo & Desruisseaux         Standards Track                   [Page 78]

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