Network Working Group Tony Small, Microsoft Corporation
INTERNET-DRAFT Denis Hennessy, ISOCOR
Calendaring and Scheduling Working Group
Frank Dawson, Lotus
Expires six months from June 11, 1998
Calendar attributes for vCard and LDAP
draft-ietf-calsch-locating-00.txt
Status of this Memo
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Abstract
When scheduling a calendar entity, such as an event, it is a
prerequisite that an organizer has the calendar address of each
attendee that will be invited to the event. Additionally, access to an
attendee's current "busy time" provides an a priori indication of
whether the attendee will be free to participate in the event.
In order to meet these challenges, a calendar user agent (CUA) needs a
mechanism to locate (URI) individual user's calendar and free/busy
time.
This draft defines three mechanisms for obtaining a URI to a user's
calendar and free/busy time. These include:
- Manual transfer of the information;
- Personal data exchange using the vCard format; and
- Directory lookup using the LDAP protocol.
1. URIs
This draft defines four classes of URIs. URIs are more useful if it is
understood what the URIs point to. Here is a brief description:
INTERNET-DRAFT Locating A Calendar User June 1998
1.1. Free/Busy URI (FBURL)
The free/busy URI is defined to be a transport independent location
where a client can obtain information about when a user is busy. At the
present time, this URI only points to busy time data. Future revisions
of this specification may provide for the extended capability of
publishing free time data.
If a calendaring and scheduling client (i.e., CUA) were to retrieve
data from this location using FTP or HTTP, it would get back an
iCalendar object [10] containing one or more "VFREEBUSY" calendar
components. If a MIME transport is being used, the response will be
contained within a "text/calendar" MIME body part as specified in the
iCalendar specification [10]. For example:
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//hacksw/handcal//NONSGML v1.0//EN
METHOD:PUBLISH
BEGIN:VFREEBUSY
ATTENDEE:MAILTO:jane_doe@host1.com
DTSTART:19971013T050000Z
DTEND:19971124T050000Z
DTSTAMP:19970901T083000Z
FREEBUSY:19971015T133000Z/19971015T180000Z
FREEBUSY:19971015T190000Z/19971015T220000Z
FBURL:http://www.host.com/calendar/busy/jdoe.ifb
END:VFREEBUSY
END:VCALENDAR
The amount of busy time data pointed to by the FBURL will generally be
pre-determined; for example one month of free/busy inforation. As a
guideline, it is recommended that the previous six weeks of busy time
data be published at the location associated with the FBURL. If this
URI points to a file resource, it is recommended that the file
extension be "ifb" to distinguish it from an arbitrary iCalendar
object.
1.2 Calendar Address URI (CALADRURI)
The calendar address URI is defined to be a transport independent
communication end-point for a user. The organizer's calendaring and
scheduling client (ie. CUA) would use this URI to determine where to
send an event request when organizing a meeting with a particular
attendee.
If the user prefers to receive event requests via iMIP, then the user
would provide a "mailto" URI containing the user's e-mail address. [13]
For example:
"mailto:user@host1.com"
INTERNET-DRAFT Locating A Calendar User June 1998
The URI for an iRIP user is yet to be defined, but that is another
possible URI value in this property. [14]
1.3. Calendar Access URI (CAPURI)
The Calendar Access URI is defined to be a protocol independent
location from which a calendaring and scheduling client (i.e., CUA) can
communicate with a user's entire calendar.
The semantics for using this URI as an access protocol locator are yet
to be defined by the IETF CALSCH Working Group. This will be addressed
in the "Calendar Access Protocol" specification.
1.4 Calendar URI (CALURI)
The Calendar URI is defined to be a protocol independent location from
which a calendaring and scheduling client (ie. CUA) can retrieve an
entire copy of a user's calendar. Retrieving data from this URI
obtains a published "snapshot" of the user's calendar.
HTTP URI -- If the URI is an HTTP URI, then the content returned with a
GET should be a "text/calendar" MIME body part containing one or more
iCalendar object.
FTP URI -- If the URI is an FTP URI, then the resource pointed to
should be a file with an "ics" file extension containing one or more
iCalendar objects.
1.5. Default URIs
There are many cases where a user may have more than one calendar. In
these cases, a user may have multiple URIs, each URI pointing to a
calendar or free/busy data.
To make the case of multiple calendars simpler for clients, the concept
of the "default" calendar is introduced. A "default" calendar is one
that the user has designated as the calendar that other users should
look at when accessing the user's calendar, or retrieving the user's
free/busy time.
The default calendar may, in fact, include rolled-up information from
all the user's other calendars. The other calendars may only exist for
organizational purposes.
2. Distribution
These four URIs provide valuable pointers to calendaring and scheduling
data that other users need in order to know when to schedule meetings,
INTERNET-DRAFT Locating A Calendar User June 1998
etc. There are several possibilities on how users can communicate
these URIs to other users. The following section outlines how these
URIs can be distributed to other users.
2.1. Manual Transfer
The simplest way to obtain these URIs is for a user to communicate the
URIs using some out-of-band mechanism such as verbally, or in an e-mail
message, or by printing these URIs on a paper business card.
When using this mechanism, the user obtains these URIs using an out-of-
band mechanism and then enters these URIs into their calendaring
software manually.
2.2. Personal Data Exchange Using A vCard
A more sophisticated way to obtain these URIs is for users to publish
vCards containing these URIs. The vCard object can be transferred
between one another. Since many e-mail clients allow a user to
automatically include a vCard with every message that the user sends,
this provides a simple, transparent way for a user to distribute their
calendaring and scheduling URIs.
On the receiving end, an e-mail client that provides an integrated
vCard database can provide a way to lookup calendaring URIs for users
whose vCards are stored locally.
2.2.1. vCard Schema Extensions
Since the vCard [8] specification doesn't specify how to encode
calendaring URIs in a vCard, this section is provided as an extension
to vCard which specifies how to encode calendaring URIs within a vCard.
Inside a vCard object, four new properties are defined: "CALURI",
_CAPURI_, _CALADRURI_, and "FBURL", as defined above.
Any vCard can have one or more of these properties, each representing a
calendar or free/busy time that is associated with the user.
One of these properties can be designated as the "default" by adding
the "PREF" parameter.
Here is a simple example of a vCard containing a "FBURL" and a
"CALURI".
BEGIN:VCARD
VERSION:3.0
FN:Alec Dun
N:Dun;Alec
INTERNET-DRAFT Locating A Calendar User June 1998
ORG:Microsoft Corporation
ADR;WORK;POSTAL;PARCEL:;;One Microsoft Way;
Redmond;WA;98052-6399;USA
TEL;WORK;MSG:+1-206-936-4544
TEL;WORK;FAX:+1-206-936-7329
EMAIL;INTERNET:user@host1.com
CALADRURI;PREF:mailto:user@host1.com
CALURI;PREF:http://cal.host1.com/user/cal.ics
FBURL;PREF:http://cal.host1.com/user/fb.ifb
CALURI:http://cal.company.com/projectA/pjtA.ics
FBURL:http://cal.company.com/projectA/pjtAfb.ifb
END:VCARD
2.2.1.1 FBURL Property IANA Registration
To: ietf-mime-directory@imc.org
Subject: Registration of FBURL type for text/directory MIME type
vCard profile.
Type name: FBURL
Type purpose: To specify the URI for a user's busy time in a vCard
object.
Type encoding: 8bit
Type value: A single URI value.
Type special notes: Where multiple FBURL properties are specified,
the default FBURL property is indicated with the PREF
parameter. The FTP or HTTP type of URI points to an iCalendar
object associated with a snapshot of the last six weeks of the
user's busy time data. If the iCalendar object is represented
as a file or document, it's file type should be "ifb".
Intended usage: Refer to section 1.1.
Type examples:
FBURL;PREF:http://www.host1.com/busy/janedoe
FBURL:FTP://ftp.host.com/busy/project-a.ifb
2.2.1.2 CALADRURI Property IANA Registration
To: ietf-mime-directory@imc.org
Subject: Registration of CALADRURI type for application/directory
MIME type vCard profile.
Type name: CALADRURI
Type purpose: To specify the location to which an event request
should be sent for the user.
Type encoding: 8bit
Type value: A single URI value.
Type special notes: Where multiple CALADRURI properties are
specified, the default CALADRURI property is indicated with the
PREF parameter.
Intended usage: Refer to section 1.2.
INTERNET-DRAFT Locating A Calendar User June 1998
Type examples:
CALADRURI;PREF:mailto:janedoe@host.com
2.2.1.3 CAPURI Property IANA Registration
To: ietf-mime-directory@imc.org
Subject: Registration of CAPURI type for application/directory MIME
type vCard profile.
Type name: CAPURI
Type purpose: To specify a protocol independent location from which
a calendaring and scheduling client (i.e., CUA) can communicate
with a user's entire calendar.
Type encoding: 8bit
Type value: A single URI value.
Type special notes: Where multiple CAPURI properties are specified,
the default CAPURI property is indicated with the PREF
parameter.
Intended usage: Refer to section 1.3.
2.2.1.4 CALURI Property IANA Registration
To: ietf-mime-directory@imc.org
Subject: Registration of CALURI type for text/directory MIME type
vCard profile.
Type name: CALURI
Type purpose: To specify the URI for a user's calendar in a vCard
object.
Type encoding: 8bit
Type valuetype: A single URI value.
Type special notes: Where multiple CALURI properties are specified,
the default CALURI property is indicated with the PREF
parameter. The property should contain a URI pointing to an
iCalendar object associated with a snapshot of the user's
calendar store. If the iCalendar object is represented as a
file or document, it's file type should be "ics".
Intended usage: Refer to section 1.4.
Type examples:
CALURI;PREF:http://cal.host1.com/calA
CALURI:ftp://ftp.host1.com/calA.ics
2.3. Directory Lookup Using The LDAP v3 Protocol
Another way to obtain these URIs is to look them up in a directory
using the LDAP protocol.
If an organizer knows an attendee's e-mail address, then using DNS,
the attendee's directory server can be found. The mechanism for this
is described in detail in [7]. From the directory server, the client
INTERNET-DRAFT Locating A Calendar User June 1998
can look up the URLs for a user's calendar. Here's a summary of how it
works. For more detail, please see the draft [7].
The client first parses the domain name out from the rfc822 mailbox
name. For the fictitious mailbox "janedoe@host1.com", the domain name
would be "host1.com".
Given the domain name, the client prepends "ldap.tcp" to the domain
name and formulating a host. Next the client retrieves the queries the
DNS server for the SRV record for "ldap.tcp.host1.com". The mechanism
for adding "ldap.tcp" onto the original domain name is described in
detail in [5]. The DNS server returns the IP address for the
associated server for 'ldap.tcp.host1.com'.
Once the IP address for the LDAP server has been obtained, the client
constructs a DN from which to search using the DNS name. In this case,
it would be "DC=host1,DC=COM". The mechanism to construct the DN is
described in detail in [6]. With the IP address and the DN, the client
issues a search request to the server where the attribute named "mail"
[4] "equalityMatch"es the user's email address. From the first
matching entry, client obtains the calendaring and scheduling URLs.
If a user's URIs can be found using directory lookup, they should, in
general, be considered "more up-to-date" than URIs in any vCards that
are stored locally.
2.3.1. LDAP Schema Extensions
In order to encode the calendaring URIs in the directory, the following
are defined:
one object class:
@ calEntry
and eight attributes:
@ calCalURI
@ calFBURL
@ calCAPURI
@ calCalAdrURI
@ calOtherCalURIs
@ calOtherFBURLs
@ calOtherCAPURIs
@ calOtherCalAdrURIs
The calCalURI contains the URI to a snapshot of the user's entire
default calendar. The calFBURL contains the URI to the user's default
busy time data. The calCAPURI represents contains a URI that can be
used to communicate with the user's calendar. The calCalAdrURI
INTERNET-DRAFT Locating A Calendar User June 1998
contains a URI that points to the location to which event requests
should be sent for that user.
The calOtherCalURIs is a multi-valued property containing URIs to
snapshots of other calendars that the user may have. The
calOtherFBURLs is a multi-valued property containing URIs to other
free/busy data that the user may have. The calOtherCAPURIs attribute
is a multi-valued property containing URIs to other calendars that the
user may have. The calOtherCalAdrURIs attribute is a multi-valued
property containing URIs to other locations that a user may want event
requests sent to.
There is no predetermined order to the values in either multi-valued
property.
2.3.2. Notation
The notation used in this document is the same as that used in [2].
2.3.3. Object Definitions
2.3.3.1. calEntry
The Calendar Entry is a class derived from _TOP_ [2], which contains
the four calendaring attributes.
( 1.2.840.113556.1.5.87
NAME 'calEntry'
TOP
AUXILIARY
MAY (calCalURI calFBURL calOtherCalURIs calOtherFBURLs
calCAPURI calOtherCAPURLs)
)
2.3.4. Attribute Definitions
2.3.4.1. calCalURI
( 1.2.840.113556.1.4.478
NAME 'calCalURI'
EQUALITY caseIgnoreMatch
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
USAGE userApplications
)
2.3.4.2. calFBURL
INTERNET-DRAFT Locating A Calendar User June 1998
( 1.2.840.113556.1.4.479
NAME 'calFBURL'
EQUALITY caseIgnoreMatch
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
USAGE userApplications
)
2.3.4.3. calCAPURI
( 1.2.840.113556.1.4.480
NAME 'calCAPURI'
EQUALITY caseIgnoreMatch
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
USAGE userApplications
)
2.3.4.4. calCalAdrURI
( 1.2.840.113556.1.4.481
NAME 'calCalAdrURI'
EQUALITY caseIgnoreMatch
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
USAGE userApplications
)
2.3.4.5. calOtherCalURIs
( 1.2.840.113556.1.4.482
NAME 'calOtherCalURIs'
EQUALITY caseIgnoreMatch
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
MULTI-VALUE
USAGE userApplications
)
2.3.4.6. calOtherFBURLs
( 1.2.840.113556.1.4.483
NAME 'calOtherFBURLs'
EQUALITY caseIgnoreMatch
INTERNET-DRAFT Locating A Calendar User June 1998
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
MULTI-VALUE
USAGE userApplications
)
2.3.4.7. calOtherCAPURIs
( 1.2.840.113556.1.4.484
NAME 'calOtherCAPURIs'
EQUALITY caseIgnoreMatch
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
MULTI-VALUE
USAGE userApplications
)
2.3.4.8. calOtherCalAdrURIs
( 1.2.840.113556.1.4.485
NAME 'calOtherCalAdrURIs'
EQUALITY caseIgnoreMatch
SUBSTRING caseIgnoreMatch
SYNTAX 'Directory String'
MULTI-VALUE
USAGE userApplications
)
Authors' Addresses
BEGIN:VCARD
VERSION:2.1
N:Small;Tony
FN:Tony Small
ORG:Microsoft Corporation
ADR;WORK;POSTAL;PARCEL:;;One Microsoft Way;
Redmond;WA;98052-6399;USA
TEL;WORK;MSG:+1-425-703-2190
TEL;WORK;FAX:+1-206-936-7329
EMAIL;INTERNET:tonysm@Microsoft.com
CALADRURI:MAIL-TO:tonysm@Microsoft.com
END:VCARD
BEGIN:VCARD
VERSION:2.1
N:Hennessy;Denis
FN:Denis Hennessy
INTERNET-DRAFT Locating A Calendar User June 1998
ORG:ISOCOR
ADR;WORK;POSTAL;PARCEL:;;42-47 Lower Mount St;
Dublin 2;Ireland
TEL;WORK;MSG:+353-1-676-0366
TEL;WORK;FAX:+353-1-676-0856
EMAIL;INTERNET:denis.hennessy@isocor.com
CALADRURI:MAIL-TO:denis.hennessy@isocor.com
END:VCARD
BEGIN:VCARD
VERSION:2.1
N:Dawson;Frank
FN:Frank Dawson
ORG:Lotus Development Corporation
ADR;WORK;POSTAL;PARCEL:;;6544 Battleford Drive;
Raleigh;NC;27613-3502;USA
TEL;WORK;MSG:+1-919-676-9515
TEL;WORK;FAX:+1-919-676-9564
EMAIL;INTERNET;PREF:Frank_Dawson@Lotus.com
EMAIL;INTERNET:fdawson@earthlink.net
CALADRURI;PREF:MAIL-TO:Frank_Dawson@Lotus.com
CALADRURI:MAIL-TO:fdawson@earthlink.net
URI:http://home.earthlink.net/~fdawson
END:VCARD
Bibliography
[1] M. Wahl, T. Howes, S. Kille, 'Lightweight Directory Access
Protocol (v3)', RFC 2251, December 1997,
<URL:ftp://ds.internic.net/rfc/rfc2251.txt>
[2] M. Wahl, A. Coulbeck, T. Howes, S. Kille, 'Lightweight Directory
Access Protocol (v3): Attribute Syntax Definitions', RFC 2252,
December 1997, <URL:ftp://ds.internic.net/rfc/rfc2252.txt>
[3] M. Wahl, A Summary of the X.500(96) User Schema for use with
LDAPv3',
RFC 2256, December 1997,
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[4] The Directory: Selected Attribute Types. ITU-T Recommendation
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[5] The Directory: Selected Object Classes. ITU-T Recommendation
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INTERNET-DRAFT Locating A Calendar User June 1998
[7] P. Leach `Locating Native Internet LDAP Servers',
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March 1997
[8] F. Dawson, T. Howes, 'vCard MIME Directory Profile',
INTERNET-DRAFT <draft-ietf-asid-mime-vcard-03.txt>,
July 1997
[9] A. Gulbrandsen, P. Vixie, "A DNS RR for specifying the location
of services (DNS SRV)", RFC 2052,
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[10] F. Dawson, D. Stenerson 'Internet Calendaring and Scheduling
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05.txt
>
[11] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, USC/Information Sciences
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[12] Network Applications Consortium 'Lightweight Internet Person
Schema', April 1997, <URL:http://www.netapps.org>
[13] F. Dawson, S. Mansour `iCalendar Message-Based Interopability
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>
[14] A.
Courtemanche, S. Mansour, P. O'Leary `iCalendar Real-Time
Interopability Protocol (
iRIP)', November 1997, <URL:
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