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Versions: 00 01 02 03 04                                                
Network Working Group                          Andre Courtemanche, CS&T
Internet Draft                                      Frank Dawson, Lotus
<draft-ietf-calsch-capreq-04.txt>               Steve Mansour, Netscape
                                                Pete O'Leary, Amplitude
                                           Doug Royer, Sun Microsystems
                                                  Tony Small, Microsoft
Expires six months after:                             November 17, 2000

                            CAP Requirements

Status of this Memo

   This document is an Internet-Draft. Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups. Note that other groups may also distribute
   working documents as Internet-Drafts.


   This document is an Internet-Draft and is in full conformance with all
   provisions of Section 10 of RFC2026.


   Internet-Drafts are draft documents valid for a maximum of six
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   Distribution of this document is unlimited.

Abstract

   The Calendar Access Protocol (CAP) is an Internet protocol for
   accessing an [ICAL] based calendar store (CS) from a calendar user
   agent (CUA). The purpose of this document is to set forth a list of
   requirements that CAP MUST address in order to meet the needs of the
   calendaring and scheduling community.

   This document is based on discussions within the Internet Engineering
   Task Force (IETF) Calendaring and Scheduling (CALSCH) working group.
   More information about the IETF CALSCH working group activities can
   be found on the IMC web site at http://www.imc.org, the IETF web site
   at http://www.ietf.org/html.charters/calsch-charter.html. Refer to
   the references within this document for further information on how to
   access these various documents.

   Distribution of this document is unlimited. Comments and suggestions
   for improvement should be sent to the authors.

   Copyright (C) The Internet Society 1998. All Rights Reserved.

Change History

   Version 00 - Initial draft.


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   Version 01 - Revised format; Included initial set of scenarios and
   requirements.

   Version 02 - Revised format; Significant modification to set of
   requirements. Included lists of requirements that are deferred to
   later versions of CAP or to other drafts.

   Version 03 - Resubmittal because draft expired.  Work is continuing
   on CAP draft.  Added line about RFC2026 conformance.
















































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Table of Contents
1. Introduction........................................................4
2. Terminology.........................................................4
3. Relationship To iCalendar, iTIP and iMIP/iRIP.......................7
4. Requirements........................................................7
 4.1 Basic Usage ......................................................7
 4.2 Infrastructure ...................................................8
  4.2.1 Connection Models .............................................8
  4.2.2 Store Location Models .........................................9
  4.2.3 Calendar Stores ..............................................10
  4.2.4 Exception Reporting ..........................................11
 4.3 Operations on a Calendar ........................................11
  4.3.1 Deferred Requirements for Operations on a Calendar ...........12
 4.4 Component Management ............................................12
  4.4.1 Recurrence ...................................................13
  4.4.2 Calendar and Component Policies ..............................14
  4.4.3 Deferred Requirements for Component Management ...............14
 4.5 Lookup, Query and Discovery .....................................15
  4.5.1 Lookup .......................................................15
  4.5.2 Query Capabilities ...........................................15
  4.5.3 Specific Queries .............................................17
  4.5.4 Discovery ....................................................17
  4.5.5 Deferred Requirements for Search .............................18
 4.6 Security ........................................................18
 4.7 Designates and Delegation .......................................18
 4.8 Notification (deferred) .........................................19
 4.9 Access Control (deferred) .......................................19
 4.10 Resource Groups and Pools (deferred) ...........................20
 4.11 CAP Non-requirements ...........................................21
5. Open Issues........................................................21
6. Acknowledgments....................................................22
7. Bibliography.......................................................22
8. Authors' Address...................................................22
9. Full Copyright Statement...........................................24




















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1.      Introduction

   The Calendar Access Protocol (CAP) is an Internet protocol for
   accessing an [ICAL] based calendar store (CS) from a calendar user
   agent (CUA). The purpose of this document is to set forth a list of
   requirements that CAP MUST address in order to meet the needs of the
   calendaring and scheduling community.

2.      Terminology

   The terminology used in [ICAL], [ITIP] and [IMIP] are also used
   within this memo.

     Calendar
       A collection of logically related objects or entities each of
       which may be associated with a calendar date and possibly time of
       day. These entities can include other calendar properties or
       calendar components. In addition, a calendar might be
       hierarchically structured and consist of other sub-calendars. The
       [ICAL] defines calendar properties, calendar components and
       component properties. A calendar is identified by its unique
       calendar identifier.

     Calendar Access Protocol
       An Internet protocol that allows a CUA to access and operate on a
       CS.

     Calendar Access Rights
       Some method for specifying permitted operational capabilities for
       a calendar user.

     Calendar Component
       An entity within a calendar. Types of calendar components include
       events, to-dos, journals, alarms, time zones and freebusy data. A
       calendar component consists of component properties and possibly
       other sub-components. For example, an event can consist of an
       alarm component.

     Calendar Component Properties
       An attribute of a particular calendar component. Some calendar
       component properties are applicable to different types of
       calendar components. For example, DTSTART is applicable to
       VEVENT, VTODO, VJOURNAL calendar components. Other calendar
       components are applicable only to an individual type of calendar
       component. For example, TZURL is only applicable to VTIMEZONE
       calendar components.

     Calendar Identifier
       Also known as "CalID". A globally unique identifier associated
       with a calendar within a CS.




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     Calendar Policy
       An operational restriction on the access or manipulation of a
       calendar. For example, "events MUST be scheduled in unit
       intervals of one hour".

     Calendar Properties
       An attribute of a calendar. The attibute applies to the calendar,
       as a whole. For example, CALSCALE specifies the calendar scale
       (e.g., GREGORIAN) for the whole calendar.

     Calendar Service
       An implementation of an application that manages one or more
       calendars.

     Calendar Store
       Also known as "CS". The data model definition for a Calendar
       Service.

     Calendar Store Identifier
       Also known as "CSID". The identifier for an individual calendar
       store. A CSID consists of the user, password, host and port
       portions of a "Common Internet Scheme Syntax" part of a URL, as
       defined by [RFC1738].

     Calendar Store Components
       Components maintained in a Calendar Store that are not part of
       any calendar.

     Calendar Store Properties
       Properties maintained in a Calendar Store that are not part of
       any calendar.

     Calendar User
       The entity that is associated with the credentials presented by
       the Calendar User Agent to the Calendar Store.

     Calendar User Agent
       Also known as "CUA". The CUA is the software client operated by
       the calendar user.

     Calendaring and Scheduling System
       The computer sub-system that provides the services for accessing,
       manipulating calendars and scheduling calendar components.

     Connected Mode
       A mobile computing mode where the CUA is directly connected to
       the calendar store.

     Delegate
       Is a calendar user (sometimes called the delegatee) who has been
       assigned participation in a scheduled calendar component (e.g.,
       VEVENT) by one of the attendees in the scheduled calendar
       component (sometimes called the delegator). An example of a
       delegate is a team member told to go to a particular meeting.

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     Designate
       Is a calendar user who is authorized to act on behalf of another
       calendar user. An example of a designate is an assistant.

     Disconnected Mode
       A mobile computing mode where a CUA can be disconnected from a
       calendar store. When the CUA is disconnected, it is in the
       disconnected mode.

     Fan Out
       The process by which a calendar store forwards scheduling
       operations to the attendees not associated with the current
       calendar.

     Hierarchical Calendars
       A CS feature where calendars may contain sub-calendars. The top-
       most calendar in a hierarchy of calendars is called the root
       calendar. There may be multiple root calendars in a single CS.
       Within a hierarchy of calendars, all sub-calendars have a
       calendar with a parent topographical relationship. In addition,
       sub-calendars may have sub-calendars (child topographical
       relationship). In addition, the sub-calendar may have one or more
       calendars with a sibling topographical relationship.

     High Bandwidth Connection
       A communications connection supporting high transfer rates;
       transfer rates commonly found within a LAN.

     Local Store
       A store which is on the same hardware as the CUA.

     Low Bandwidth Connection
       A communications connection supporting slow transfer rates;
       transfer rates commonly found in modem technology.

     Relative Calendar Identifier
       Also known as "Relative CalID". A relative identifier for an
       individual calendar in a calendar store. A Relative CalID
       consists of the portion of the "scheme part" of a Qualified
       CalID, following the Calendar Store Identifier. This is the same
       as the "URL path" of the "Common Internet Scheme Syntax" portion
       of a URL, as defined by [RFC1738].

     Qualified Calendar Identifier
       Also known as "Qualified CalID". A complete Internet identifier
       for a specific calendar. A Qualified CalID consists of a CAP
       specific "scheme" and "scheme part" portion of a URL, as defined
       in [RFC1738]. A Qualified CalID are written only with the graphic
       printable characters of the US-ASCII coded character set.

     Remote Store
       A store which is not on the same hardware as the CUA.



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     Sub-calendars
       Calendars that are contained within other calendars in a
       hierarchical relationship.

3.      Relationship To iCalendar, iTIP and iMIP/iRIP

   The CAP data elements MUST be based on the calendar architecture set
   forth in [ICAL]. More precisely, CAP will define an Internet protocol
   for accessing a CS that consists of one or more calendars, each
   consisting of numerous [ICAL] components. The definition of CAP might
   necessitate adding components, properties, parameters and other
   elements beyond those defined in [ICAL]. These additions MUST be
   defined in a manner consistent with and upwards compatible to the
   data model defined by [ICAL].

   Where it makes practical sense, CAP SHOULD make use of the scheduling
   workflow defined by [ITIP].

   CAP will not require that [IMIP] or [IRIP] MUST be used to
   communicate with other calendar users.

4.      Requirements

4.1     Basic Usage

   CAP MUST specify:

     - How to provide a standard protocol to allow a CUA to
     interoperate with a CS.

     - Using only CAP, a CUA MUST be able to access and manipulate a
     calendar. CAP MUST provide the complete, if minimal, functionality
     that allows a CUA to access a calendar.

     - How to allow a CUA to be developed independently of a CS and a
     CS independently of a CUA.

     - How to allow an organization to have a mixture of CUAs and CSs
     from different vendors. With CAP, any CUA in the organization MUST
     be able to interoperate with any CS.

     - How to allow for a single CUA to access multiple CSs or
     calendars.

       For example, a CUA MUST be able to create calendar components on
       multiple calendars and/or retrieve calendar components from
       multiple calendars.

     - How to allow for a rich featured CUA.

       For example, allow a CUA to be part of a client which offers
       rich calendaring, scheduling and related functionality, with the
       possibility of extending from concepts and services offered by
       CAP, while still using CAP to access a calendar.

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     - How to extend the base features in CAP.

     - How to allow for interpersonal applications to be calendar
     enabled.

       For example, a chat application MUST be able to offer a calendar
       button to create an event between the two or more parties.

     - How to allow for non-interpersonal applications to be calendar
     enabled.

       For example, a reservation system MUST be able to retrieve and
       update calendar components from a calendar. Other examples of
       non-interpersonal applications include event planning, resource
       scheduling, and Human Asset Management (HAM).

     - How to allow for CUAs without local store and with minimal
     memory.

       For example, a cell phone MUST be able to act as a CUA.

     - How to allow for CUAs with local store that can be kept
     synchronized with the remote store.

       For example, a robust featured application might act as a CUA
       and also provide extra functionality using the local store.

     - How to allow for CUAs over disconnected, low-bandwidth
     connections.

       For example, a PDA MUST be able to act as a CUA and interoperate
       with a CS over a low-bandwidth wireless connection.

     - How to allow for CUAs over high bandwidth connections.

       For example, a PC MUST be able to act as a CUA and interoperate
       with a CS over a high-speed Ethernet connection.

4.2     Infrastructure

   This section defines a set of infrastructure requirements for CAP.

4.2.1   Connection Models

   CAP MUST support a number of CUA-to-CS connection models. In
   particular, CAP MUST allow connected and disconnected operation.

   CUAs and CSs often support the "connected model", where clients
   maintain long-term connections to servers. Because of this, CAP MUST
   specify how the connection between a CUA and a CS can be maintained.

   CAP MUST NOT prevent servers from dropping client connections,
   particularly idle client connections. CAP MUST provide some ways for
   clients to indicate that they would like to stay connected, or that

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   they would like to drop the connection after the current
   request/response. These requirements are open issues.

4.2.2   Store Location Models

   CAP MUST allow CUAs with local stores and CUAs without local stores.

SINGLE REMOTE CS

   CAP MUST support the store location model where a CUA needs to
   retrieve everything from a single remote CS. In this model, the CUA
   does not have a local CS. Instead, a single CS resides remotely and
   is accessed through CAP. The client MUST always establish the CAP
   connection in order to function.

MULTIPLE REMOTE CS

   CAP MUST support the model where a CUA has no local CS, but needs to
   retrieve everything from multiple remote CS. In this model, the CUA
   does not have any local CS. Instead, multiple CSs reside remotely and
   are accessed through CAP. The client MUST always establish one or
   more CAP connections in order to function.

SINGLE LOCAL, SINGLE REMOTE CS

   CAP MUST support the model where a CUA can retrieve everything from
   the local store and periodically synchronize the local store with a
   single remote CS. When there is no CAP connection, the CUA can still
   function. When the CAP connection is re-established, the CUA can
   update the remote CS with information modified on the local CS while
   it was disconnected. In addition, the CUA can update its single local
   CS with information that was modified on the remote CS while the CUA
   was disconnected.

SINGLE LOCAL, MULTIPLE REMOTE CS

   CAP MUST support the model where a CUA can retrieve everything from a
   local CS and periodically synchronize with multiple remote CS. When
   the CAP connection is not established, the CUA can still function.
   When the CUA re-establishes a connection with each remote CS, it can
   update the remote CS with information modified while disconnected. In
   addition, the CUA can update the single local CS with information
   that was modified on remote CS while the CUA was disconnected.

MULTIPLE LOCAL, MULTIPLE REMOTE CS

   CAP MUST support the model where a CUA can retrieve everything from
   multiple local CS and periodically synchronize them with multiple
   remote CS. When a CAP connection is not established, the CUA can
   still function. When the CUA re-establishes a connection with each
   remote CS, it can update the remote CS with information modified
   while disconnected. In addition, the CS associated with the CAP
   connection can update any of the local CS with information that was


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   modified while it was disconnected from the remote CS. Multiple local
   and remote CS can be updated in sequence.

   When remote and local CSs are involved, it MUST be possible to
   identify conflicts between the local and remote CSs. It is the
   responsibility of the CUA to resolve conflicts.

   "Modified information" includes new, changed and deleted components,
   as well as properties on calendars and components.

4.2.3   Calendar Stores

   The diagram below describes the data objects maintained in a CS. CAP
   defines how data in the CS is manipulated. The data consists of:

     - Calendar Store properties, e.g. local time zone

     - Calendars, e.g. a user's calendar

     - Calendar properties, e.g. a user name

     - Calendar components, e.g. an iCAL VEVENT

     - Component properties, e.g. DTSTART on a VEVENT

     - Property attributes, e.g. TZID on DTSTART

     - Access control rights (deferred)

   A calendar may contain other calendars to form a hierarchy. Every
   calendar has its own properties.

   CAP does not define users. CAP does not define any default or implied
   relationship between a user and a calendar. Users, via a CUA,
   authenticate themselves to a CS to access information. All access is
   subject to access control.

        Editor Note: Insert calendar store diagram here. In the interim
        refer to http://www.imc.org/ietf-calendar/csmodel.jpg

   Calendars are always referenced by their CalIDs. Open issue: whether
   calendars can also be referenced by their hierarchical name.

   CalIDs are used in all operations

   Attendees values can be Qualified CalIDs of varying schemes. For
   example:

   ATTENDEE[...]:mailto:a@example.com
   ATTENDEE[...]:irip://cal-1.example.com/b
   ATTENDEE[...]:cap://calendar.example.com/c

        Editor Note: The MAILTO URL is illustrating an "iMIP" URL.


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   CAP MUST provide a way for the CUA to determine whether or not the CS
   supports optional or varying capabilities. For example:

     - Is a particular optional feature (like fan out, or calendar
     access rights) supported?

     - Determine what, if any, limitation the CS imposes on unbounded
     recurrence rules.

     - Provide a way for the CUA to determine what, if any, limitations
     the CS imposes on date/time values. For example, there may be dates
     in the past and future beyond which the CS cannot represent.

4.2.4   Exception Reporting

   The granularity of exception report can be at the level of the
   calendar, the calendar component, component property, or property
   attribute as appropriate.

   CAP MUST provide a way to determine the results of delayed
   operations. Delayed operations arise from the use of other protocols
   (IMIP, IRIP), which may take a long time to resolve. Delayed
   operations have a return code and may have associated calendar data.
   As an example, an ITIP request for free/busy information may result
   in the delivery of a VFREEBUSY component. A CUA MUST be able to use
   CAP to retrieve the VFREEBUSY component. If the operation failed, the
   CUA MUST be able to determine the reply code. It is an open issue
   whether CAP MUST support delayed operations and what that means, and
   how results are returned.

4.3     Operations on a Calendar

   A calendar is assumed to reside on a CS. CAP MUST specify:

     - How a CUA can create a calendar or sub-calendar.

       For example, sub-calendars might be used to organize calendar
       information based on criteria defined by the CUA.

     - How a CUA can rename a calendar or sub-calendar.

       For example, the CUA may decide to change the name of a calendar
       after the calendar has been created.

     - How a CUA can delete a calendar or sub-calendar.

       When deleting a calendar, all sub-calendars of the calendar MUST
       be deleted. This is an open issue.

     - A CUA can delete a calendar regardless of whether or not the
     calendar has any entities in it.

     - A CUA can set and retrieve properties of a calendar or sub-
     calendar on a CS.

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       This should include the ability to set and retrieve standard and
       custom properties, the time zone of a calendar, and the
       operational hours of a calendar.

       For example, the CUA may want to schedule an event based on the
       operational hours of a calendar.

4.3.1   Deferred Requirements for Operations on a Calendar

   CAP is not required to specify:

     - How to copy a calendar on a CS or between CSs.

     - How a group operations on a set of calendars.

     - How to undelete a calendar.

     - Auto processing on scheduled components in a calendar that need
     action.

       For example, if someone tries to create a meeting on a calendar
       for a user who is on vacation, the CS may automatically delegate
       the meeting to another user.

4.4     Component Management

   CAP MUST specify, subject to access control:

     - How the CUA can create a component (event/to-do/journal) on a
     calendar (direct booking)

     - How the CUA can create a component on another user's calendar

       This capability permits the CUA to create calendar components on
       another calendar, other than their own, but does not necessarily
       give them the capability to read or modify calendar components.

     - How the CUA can modify a component on a given calendar

     - How the CUA can delete a component from one or more calendars

     - The requirement to delete from multiple calendars might be met
     with separate requests.

     - How the CUA can modify, add or delete an arbitrary component
     property within a specified calendar.

       For example, modify the SUMMARY property on a calendar
       component.

     - How the CUA can modify a parameter of a multi-valued component
     property within a specified calendar.



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       For example, modify the PARTSTAT parameter on an ATTENDEE
       property associated with a particular attendee on a calendar
       component.

     - How the CUA can add or modify attachment properties on a
     specified component.

       The attachments may be large, and the CUA ought not have to
       resend the entire component.

     - How the CUA can send an attachment to the CS.

       The attachment would be appended to a particular component.

     - How the CUA can remove a specified attachment from the CS and
     its property from the specified component.

     - How hierarchical name can be used for all operations.

       This requirement indicates that any calendaring or scheduling
       operation performed on a component or calendar by specifying the
       UID or CSID, MUST also be available by specifying the
       hierarchical name. The two exceptions are the request for the
       hierarchical name given the UID or vice versa.

       Open Issue: This is still open to discussion.

   CAP MUST also allow the CUA to do synchronization of two calendars to
   which it has access.

4.4.1   Recurrence

   CAP MUST specify, subject to access control:

     - How the CUA can retrieve or delete a calendar component based on
     the UID, and an optional RECURRENCE-ID.

       For example, retrieve the single instance of a recurring meeting
       by specifying both the UID for the recurring meeting and the
       RECURRENCE-ID of the instance.

     - How the CUA can modify or delete an instance of a recurring
     component, or all recurrences.

     - How the CUA can modify all instances of a recurring component
     that occur before a specified date, or after a particular date.

   Open issue: whether the following requirements related to expansion
   of recurrence are deferred.

     - How the CUA can request the CS to send down components with or
     without expansion of recurring calendar components.



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     - CAP MUST permit the CS to refuse this request, so that if the CS
     normally provides expansions of recurring calendar components, it
     can refuse the request to not expand. However, the CS MUST
     terminate the expansion eventually.

     - How the CUA can find out, and perhaps change, the length of time
     for which recurring calendar components are expanded.

     - How the CUA can retrieve, and perhaps set, the period for or
     number of recurrences expanded on a recurring component.

       This could be 0, infinity, a specific DTEND, or a consistent
       length of time from "today" into the future.

4.4.2   Calendar and Component Policies

   CAP MUST specify:

     - How the CUA tells the CS to prevent conflicts (double booking)
     on a calendar

       The scenario is that a calendar could be marked for "allow no
       conflicts", and the CS would automatically prevent this. This
       might apply to direct booking or scheduling or both.

     - How operational hours for a calendar are enforced

       Each calendar MUST have a property for operational hours, and
       CAP MUST specify how the CUA tells the CS to enforce those
       operational hours. This means that the CS prevents components
       from being added in a manner that violates the operational hours
       set by the user. CAP MUST specify how policy enforcement can be
       overridden by the owner of the calendar. CAP MUST specify
       whether this includes alarms. This might apply to direct booking
       or scheduling or both.

     Open issue: Whether the ability to set a policy of turning down
     requests that exceed a maximum duration (or length of time between
     DTSTART and DTEND) is a requirement.

4.4.3   Deferred Requirements for Component Management

   CAP is not required to specify:

     - Undelete and purge deleted calendar entries.

     - Modify inline attachment to URL; provide URL to fetch.

     - Merge or aggregate more than one calendar.

     - Lock access to calendar.

     - Delayed or asynchronous transactions.


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     - The CUA requesting a size limit before retrieving components
     from the CS. The CS might send partial components if the
     component's size exceeded the limit. CAP would permdit the CS to
     refuse the request or give its preferred value.

     - The CS synchronizing 2 calendars.

     - How the CUA tells the CS to prevent conflicts with respect to an
     individual component in the calendar. The scenario for this is that
     a component could be marked for "allow no conflicts", and the CS
     would automatically prevent a new component from being added in a
     way which would cause a conflict. This might apply to either direct
     booking or scheduling or both.

     - How the CUA can create multiple entries on many CSs.

       This may occur in one or more operations, perhaps using
       different calendar protocols (CAP, iRIP, iMIP).

4.5     Lookup, Query and Discovery

   Lookup includes the capability to list things. Querying enables
   searching and filtering features. Discovery covers requests for
   information such as what features are supported by the CS.

4.5.1   Lookup

   CAP MUST specify, subject to access control:

     - How the CUA can list calendars in a single CS, by fetching all
     the top level CSIDs of the CS.

     - How the CUA can list all the sub-calendars within a given
     calendar.

     - How the CUA can list all component UIDs in a calendar.

     - How the CUA can retrieve all the free/busy data for a calendar.

     - How the CUA can retrieve a list of properties for a component or
     a set of components.

       For this requirement, the set of components is defined either as
       all the components in a calendar, or where the set of components
       is defined by a search query (search query requirements are
       elaborated in the Query Capabilities section). For example, the
       CUA could ask for the DTSTART, DTEND and SUMMARY properties for
       all components with DTSTART later than 9:00 p.m. today.

4.5.2   Query Capabilities

   CAP MUST allow the CUA to retrieve CalIDs, component UIDs or
   component hierarchical names (open issue) from a given calendar,
   using queries which specify:

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     - How the CUA can retrieve data from multiple calendars.

       This requirement allows the CUA to display multiple calendars to
       the user. This requirement does not constrain this functionality
       to a single request as it may be done in multiple requests.

     - How the CUA to retrieve any named property for a calendar or
     component.

       For example, the CUA can retrieve the SUMMARY property for a
       given component.

     - Property value equivalence query (e.g., equal to)

       For example, such as matching the organizer with a specified
       user, or matching the location with a particular conference
       room. This should work for all properties.

     - Pattern-matching string comparison query (e.g., contains)

       The pattern-matching query MUST be applied to a string property
       such as a "name" property. The response MUST include a list of
       calendar (or component) identifiers and MAY include property
       values for those items. The CUA MUST be able to request which
       properties (or the entire component) to retrieve.

     - Property value comparison query (e.g., greater than, less than)

       This requirement includes only those properties for which a
       comparison query is possible. This list of properties MUST
       include DTSTART, DTEND, DURATION. For example, this allows the
       CUA to ask for all components that begin later than (greater
       than) the specified time.

        This requirement MUST be met in a way which allows the CUA to
        discover which alarms will trigger in a given period.

     - Multiple property value comparisons combined using Boolean
     elements (e.g., logical and, logical or, negatation).

       The CUA MUST be able to discover which components have durations
       which occur at least partially in a given range of time, either
       by retrieving the list of UIDs or by retrieving all of the
       components properties. This requirement allows the CUA to
       discover all components during a particular day or other time
       period. This includes instantaneous and all-day calendar items.
       This requirement does not state that the components MUST be
       retrieved in their entirety in the same interaction as the
       query; the query and the component retrieval can be separate
       interactions between the CUA and the CS.

   CAP MUST allow synchronization, meaning at a minimum that the CUA is
   able to find and retrieve new, modified or deleted entries for a
   given time period. The CUA MUST be able to find out which entries

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   have been added, modified or deleted since it last synchronized, in
   order to operate in disconnected mode. This requirement may be
   satisfied using the query requirements already defined.

4.5.3   Specific Queries

   These are specific scenarios required by calendaring operations which
   may require special attention to ensure that they can be done with
   the querying and lookup functionality of CAP.

   CAP MUST allow, subject to access control:

     - The CUA to retrieve the CSID for a calendar specified by giving
     its hierarchical name, and vice versa.

       This requirement means that hierarchical calendar names MUST be
       unique on the CS.

       Open Issue: This is an open issue.

     - The CUA to discover conflicts given a list of calendars and a
     time period

       This feature is to allow the CUA to schedule a group of
       attendees for a meeting at a particular time; the CUA MUST be
       able to find out if those attendees are free at that time. This
       requirement does not specify whether the discovery is done
       mainly on the CS or on the CUA. For example, the CUA could ask
       for the free/busy data for each calendar during the period and
       then determine conflicts itself, or the CUA could ask the CS
       which attendees have conflicts during the period. Either
       approach would satisfy this requirement.

     - The CUA to discover which calendar components need action.

       iCalendar entries which need action include scheduled components
       that have not yet been accepted or declined. The CUA needs to
       know this list in order to present the items to the user to
       resolve them.

4.5.4   Discovery

   CAP MUST specify:

     - How the CUA can query the calendar components which are
     supported on a named calendar.

     - How the CUA can query the names of all properties which exist on
     a given calendar, or the properties which exist on a given
     component.

     - How the CUA can query the names of component properties
     supported by a CS.


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     - How the CUA can query the time zones supported by the CS

4.5.5   Deferred Requirements for Search

   CAP is not required to specify:

     - How to roll up free/busy information for a number of calendars
     (perhaps sub-calendars) into a single free/busy component.

     - How to fetch all components marked for deletion in a certain
     range. This could include components somehow marked for deletion
     but not yet purged from the CS.

     - How the CUA can determine whether the CS supports multiple
     reads/writes in the same operation.

       This would include, for example, the ability to name a number of
       calendars to add a component to in a single operation

4.6     Security

   CAP MUST specify:

     - How the CUA authenticates itself to the CS (not the calendar).

       Authentication to the CS is required for all access to the CS.
       The CS MUST be able to uniquely identify each user for the
       purposes of authentication and authorization.

     - How anonymous access to calendars is specified (if allowed).

     - How the CUA authenticates to CS using SASL.

     - How the CUA and the CS negotiate encryption mechanism for a
     secure connection.

     - How calendars can be made secure from unwanted access and false
     entries.

     - How the CUA and CS can specify denial of service to another
     calendar user.

4.7     Designates and Delegation

   CAP MUST specify, subject to access control:

     - How a list of designates is created.

     - How the CS knows that a user is a valid designate, through
     authentication or some other mechanism.

     - How the CUA can delegate to another calendar user.



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4.8     Notification (deferred)

   There are no notification features that are required in CAP.
   Notification is deemed not to be a requirement, because:

     - A CUA can poll the CS for new/changed/deleted components,
     including new ITIP messages. This functionality is needed to
     support synchronization.

     - A CUA can handle alarms on components itself.

   The notification features that were considered but have been deferred
   include:

     - Notify the CUA when a change is made to a calendar.

     - Notify the CUA when an alarm triggers.

     - Notify the CUA when a calendar component NEEDS-ACTION.

     - Notify when a CUA attempts to access a calendar, delete, modify,
     or add a calendar component.

4.9     Access Control (deferred)

   The ability to get and set access control data on calendars and
   calendar components is useful, but beyond the scope of the initial
   CAP specification. A CS may apply access control entries to calendars
   and components, but CAP need not specify how these are to be set and
   retrieved. Access control entries could be set and retrieved by
   administrators on the CS through another protocol. Additionally, a CS
   can enforce the class of each component, by restricting access to
   "confidential" and "private" components, without any design in CAP to
   allow this.

   Access control requirements that were considered but have been
   deferred include:

     - CUA query the calendar access rights for the currently
     authenticated calendar user.

     - CUA grant/deny designate rights to a given calendar user.

     - CUA removes OR denies all rights to a given calendar for given
     calendar users.

     - CUA grants free/busy view rights on a given calendar to a
     calendar user.

     - CUA grants full access rights on a given calendar to a calendar
     user.

     - CS performs calendar access rights inheritance on sub-calendars.


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     - CUA grants/denies access rights to individual properties of
     individual components.

       For example, user A can see subject of event B, or user A can
       set time of event B.

     - CUA can set operation limits for user A on calendar B.

     For example:

     - (a) set time limit C on events for user D can schedule on my
     calendar,

     - (b) set limit number of events by user E, or

     - (c) grant limited access on a calendar such that a user F can
     only create events during specified hours.

4.10    Resource Groups and Pools (deferred)

   A specification for how to handle resource groups and pools is not a
   requirement. These kinds of features will be addressed in a separate,
   later draft.

   A group has a list of members, all of whom should be included in any
   scheduled calendar component. For example, a group could contain a
   particular conference room and a particular projector, both of which
   should be scheduled for a meeting. Or a group could contain a number
   of people working together, all of whom should be scheduled for group
   meetings. When a group is included as an attendee, the CS MUST
   schedule each of the members of the group.

   A pool has a list of members, all of which are identical for the
   purposes of scheduling, and only one of them should be scheduled.
   When a pool is included as an attendee, the CS MUST schedule the
   number of them that was requested. For example, a pool could contain
   a number of VCRs, any of which can be scheduled for meetings, when
   only one VCR is usually needed.

   Resource group and pool features that were considered but were
   deferred include:

     - CUA can create a list of CSIDs which is a group or pool.

     - CUA can request to add a component to every calendar for every
     CSID in a group

     - CUA can send a single schedule request to the CS, where the
     attendee list includes a group. The CS then fans out the request.
     Fanning out might be achieved by forwarding the request to all
     members of a group, or by placing the request on the calendar of
     every member of the group. The members of the group may be on
     multiple CSs.


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     - CUA can schedule one CSID by scheduling one instance from a
     pool.

     - Each group/pool itself has properties.

     - Access restrictions can be set on a group/pool, to restrict who
     can get/set properties and who can schedule the group/pool.

4.11    CAP Non-requirements

   CAP is not required to be:

     - A client-to-client protocol.

     - A server-to-server protocol.

       For example, it would not specify how server-to-server updates
       of calendaring or scheduling operations are accomplished.

   The initial version of CAP is not required to specify:

     - How to do a full administration CUA, e.g., add user, delete
     user, move user, archive calendar, delete user, change
     user/calendar name.

     - Inheritance of calendar access rights, property values, etc.

5.      Open Issues

   Open issues include the following:

     - Whether CAP should specify how clients can request their
     connections to be kept open, and whether servers can drop
     connections at any time.

     - Whether calendars can also be referenced by their hierarchical
     name.

     - Is a particular optional feature (like fan-out, or calendar
     access rights) supported?

     - Determine what, if any, limitation the CS imposes on unbounded
     recurrence rules.

     - Whether CAP MUST support delayed operations and what that means,
     and how results are returned.

     - Whether all sub-calendars of a deleted calendar MUST be deleted.

     - Whether the ability to set a policy of turning down requests
     that exceed a maximum duration is a requirement.

     - Whether expansion of recurrences is required.


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     - Whether or not CAP operations support bounding the latency of
     responses to operations.

6.      Acknowledgments

   The following have provided input in the drafting of this memo:

   Lisa Lippert, Surendra Reddy, Richard Shusterman.

7.      Bibliography

   [ICAL] "Internet Calendaring and Scheduling Core Object Specification
   - iCalendar", RFC 2445, November 1998,
   http://www.ietf.org/rfc/rfc2445.txt.

   [ITIP] "iCalendar Transport-Independent Interoperability Protocol
   (iTIP) : Scheduling Events, Busy Time, To-dos and Journal Entries ",
   RFC 2446, November 1998, http://www.ietf.org/rfc/rfc2446.txt.

   [IMIP] "iCalendar Message-based Interoperability Protocol (iMIP), RFC
   2447, November 1998, http://www.ietf.org/rfc/rfc2447.txt.

   [IRIP] "iCalendar Message-based Interoperability Protocol (iRIP),
   Internet-Draft, November 1998, , ftp://ftp.ietf.org/internet-
   drafts/draft-ietf-calsch-irip-02.txt.

8.      Authors' Address

   The following address information is provided in a vCard v2.1,
   Electronic Business Card, format.

   BEGIN:VCARD
   VERSION:3.0
   FN:Andre Courtemanche
   N:Courtemanche;Andre
   ORG:CS&T
   ADR;TYPE=WORK,POSTAL,PARCEL:;;3333 Graham Boulevard;Montreal;QC;H3R
     3L5;Canada
   TEL;TYPE=WORK,MSG:+1-514-733-8500
   TEL;TYPE=WORK,FAX:+1-514-733-8788
   EMAIL;TYPE=INTERNET:andre@cst.ca
   END:VCARD

   BEGIN:VCARD
   VERSION:3.0
   FN:Frank Dawson
   N:Dawson;Frank
   ORG:Lotus Development Corporation
   ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive; Raleigh;
    NC;27613-3502;USA
   TEL;TYPE=WORK,MSG:+1-617-693-8728
   TEL;TYPE=WORK,FAX:+1-617-693-5552
   EMAIL;TYPE=INTERNET:Frank_Dawson@Lotus.com
   URL:http://home.earthlink.net/~fdawson

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   END:VCARD

   BEGIN:VCARD
   VERSION:3.0
   FN:Tony Small
   N:Small;Tony
   ORG:Microsoft Corporation
   ADR;TYPE=WORK,POSTAL,PARCEL:;;One Microsoft Way; Redmond;WA;
    98052-6399;USA
   TEL;TYPE=WORK,MSG:+1-206-703-2190
   TEL;TYPE=WORK,FAX:+1-206-936-7329
   EMAIL;TYPE=INTERNET:tonysm@Microsoft.com
   END:VCARD

   BEGIN:VCARD
   VERSION:3.0
   FN:Steve Mansour
   N:Mansour;Steve
   ORG:Netscape Communications Corporation
   ADR;TYPE=WORK,POSTAL,PARCEL:;;501 East Middlefield Road;Mountain
     View;CA;94043;USA
   TEL;TYPE=WORK,MSG:+1-650-937-2378
   TEL;TYPE=WORK,FAX:+1-650-937-2103
   EMAIL;TYPE=INTERNET:sman@netscape.com
   END:VCARD

   BEGIN:VCARD
   VERSION:3.0
   FN:Peter O'Leary
   N:O'Leary;Peter
   ORG:Amplitude Software Corp.
   ADR;TYPE=WORK,POSTAL,PARCEL:;;185 Berry St. Suite 4700; San
     Francisco;CA;94107;USA
   TEL;TYPE=WORK,MSG:+1-415-659-3511
   TEL;TYPE=WORK,FAX:+1-415-659-0006
   EMAIL;TYPE=INTERNET:poleary@amplitude.com
   END:VCARD

   BEGIN:VCARD
   VERSION:3.0
   FN:Doug Royer
   N:Royer;Doug
   ORG:Sun Microsystems
   ADR;TYPE=WORK,POSTAL,PARCEL:;;901 San Antonio Road, MS MPK17-105;
     Palo Alto;CA;94303;USA
   TEL;TYPE=WORK,MSG:+1-650-786-7599
   EMAIL;TYPE=INTERNET:doug.royer@sun.com
   END:VCARD

   This work is part of the Internet Engineering Task Force Calendaring
   and scheduling Working Group. The chairmen of that working group are:

   BEGIN:VCARD
   VERSION:3.0

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   FN:Anik Ganguly
   N:Ganguly;Anik
   ORG:Open Text, Inc.
   ADR;TYPE=WORK,POSTAL,PARCEL:;;38777 West Six Mile Road Suite 101;
    Livonia;MI;48152;USA
   TEL;TYPE=WORK,MSG:+1-734-542-5955
   EMAIL;TYPE=INTERNET:ganguly@acm.org
   END:VCARD

   BEGIN:VCARD
   VERSION:3.0
   FN:Robert Moskowitz
   N:Moskowitz;Robert
   EMAIL;TYPE=INTERNET:rgm-ietf@htt-consult.com
   END:VCARD

9.      Full Copyright Statement

   Copyright (C) The Internet Society (1998). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process MUST be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.













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