JEP-0149: Time Periods

This JEP defines a method to specify time periods for states, events, and activities communicated in XMPP and XMPP extensions.


WARNING: This Informational JEP is Experimental. Publication as a Jabber Enhancement Proposal does not imply approval of this proposal by the Jabber Software Foundation. Implementation of the best practice or protocol profile described herein is encouraged in exploratory implementations, although production systems should not deploy implementations of this protocol until it advances to a status of Draft.


JEP Information

Status: Experimental
Type: Informational
Number: 0149
Version: 0.1
Last Updated: 2005-04-21
JIG: Standards JIG
Approving Body: Jabber Council
Dependencies: XMPP Core, JEP-0082
Supersedes: None
Superseded By: None
Short Name: N/A
Wiki Page: <http://wiki.jabber.org/index.php/Time Periods (JEP-0149)>

Author Information

Peter Saint-Andre

Email: stpeter@jabber.org
JID: stpeter@jabber.org

Legal Notice

This Jabber Enhancement Proposal is copyright 1999 - 2005 by the Jabber Software Foundation (JSF) and is in full conformance with the JSF's Intellectual Property Rights Policy <http://www.jabber.org/jsf/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Creative Commons Attribution License (<http://creativecommons.org/licenses/by/2.5/>).

Discussion Venue

The preferred venue for discussion of this document is the Standards-JIG discussion list: <http://mail.jabber.org/mailman/listinfo/standards-jig>.

Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the Jabber Software Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this JEP has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Conformance Terms

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.


Table of Contents

1. Introduction
2. Requirements
3. Protocol
4. Examples
4.1. Basic Presence
4.2. User Activity
4.3. User Mood
5. Implementation Notes
6. Security Considerations
7. IANA Considerations
8. Jabber Registrar Considerations
8.1. SHIM Headers
9. XML Schema
Notes
Revision History


1. Introduction

Certain events and states may last for only a limited period of time. For example, when a person changes his availability to "dnd" and his status to "In a Meeting", the person (or his calendaring application) may know that the meeting is expected to last for 90 minutes; because those who subscribe to the person's presence may find it helpful to know how long the person will be in the meeting, it might be desirable to include that time period information in the presence stanza sent when the person's availability changes. Similar considerations apply to other states, events, and activities, such as "extended presence" (see Extended Presence Protocol Suite [1]).

This JEP defines a straightforward XMPP extension for encapsulating information about time periods, using new headers that adhere to the format specified in Stanza Headers and Internet Metadata (SHIM) [2].

2. Requirements

This JEP addresses the following requirements:

  1. Provide the ability to specify time periods for states, events, and activities communicated via XMPP and XMPP extensions.
  2. Conform to Jabber Date and Time Profiles [3].

3. Protocol

In order to specify the time period for a state, event, or activity, the generating entity SHOULD include both "Start" and "Stop" SHIM headers that specify the dateTimes at which the time period starts and stops. The following rules apply:

  1. All start and stop dates MUST conform to the dateTime profile specified in JEP-0082.
  2. All dateTime information MUST be expressed in UTC (i.e., with no timezone offsets).
  3. Start and stop times SHOULD be understood by the recipient as estimates or approximations.
  4. If both a start time and a stop time are specified, the stop time MUST be later than the start time.

These SHIM headers MAY be included wherever appropriate; however, it is expected that they will be included mainly to further specify basic presence states (see RFC 3921 [4]) and various "extended presence" states, events, and activities (see, for example, User Mood [5] and User Activity [6]).

There is no requirement that the start time needs to be the time when the stanza is generated; for example, the start time may be retroactive to a dateTime in the past or may be an estimated dateTime in the future.

4. Examples

4.1 Basic Presence

In order to specify that a basic presence state will last for a specific time period, the entity that generates the presence stanza SHOULD include the desired SHIM headers.

Example 1. Basic Presence With Time Period

<presence>
  <show>dnd</show>
  <status>In a Meeting</status>
  <headers xmlns='http://jabber.org/protocol/shim'>
    <header name='Stop'>2005-03-17T11:30:00Z</header>
  </headers>
</presence>
    

4.2 User Activity

An XMPP extension for user activity is specified in JEP-0108. It may be desirable to include time period information when publishing one's activity.

Example 2. User Activity With Time Period

<iq type='set' 
    from='juliet@capulet.com/balcony' 
    to='pubsub.shakespeare.lit' 
    id='activity1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='generic/juliet-activity'>
      <item id='current'>
        <activity xmlns='http://jabber.org/protocol/activity'>
          <relaxing>
            <partying/>
          </relaxing>
          <text xml:lang='en'>My best friend&apos;s birthday!</text>
        </activity>
        <headers xmlns='http://jabber.org/protocol/shim'>
          <header name='Start'>2005-03-17T19:00:00Z</header>
          <header name='Stop'>2005-03-17T23:00:00Z</header>
        </headers>
      </item>
    </publish>
  </pubsub>
</iq>
    

4.3 User Mood

An XMPP extension for user mood is specified in JEP-0107. It may be desirable to include time period information when publishing one's mood.

Example 3. User Mood With Time Period

<iq type='set' 
    from='juliet@capulet.com/balcony' 
    to='pubsub.shakespeare.lit' 
    id='mood1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='generic/juliet-mood'>
      <item id='current'>
        <mood xmlns='http://jabber.org/protocol/mood'>
          <annoyed/>
          <text>She has been bothering me *all day*!</text>
        </mood>
        <headers xmlns='http://jabber.org/protocol/shim'>
          <header name='Start'>2005-03-17T07:00:00Z</header>
        </headers>
      </item>
    </publish>
  </pubsub>
</iq>
    

Note that the start time is (intended to be) retroactive.

5. Implementation Notes

For the sake of interoperability, it may be desirable for certain kinds of implementations (e.g., gateways) to transform XMPP start and stop times into the formats used by other protocols (e.g., the 'since' and 'until' attributes specified in draft-ietf-simple-rpid [7]).

6. Security Considerations

It is possible that inclusion of time periods for particular states, events, or activities may reveal information that would enable a recipient to launch an attack while the sender is unavailable or away (e.g., if the sender specifies that he will be on vacation for the next three weeks, a recipient might therefore learn that this is a good time to break into the sender's house). Therefore, senders of time period information should balance the desire to share helpful information against the need for appropriate control over security-critical availability information.

7. IANA Considerations

This JEP requires no interaction with the Internet Assigned Numbers Authority (IANA) [8].

8. Jabber Registrar Considerations

8.1 SHIM Headers

The Jabber Registrar [9] shall include the following entries in its registry of SHIM headers.

<header>
  <name>Start</name>
  <desc>The dateTime at which a state, event, or activity starts</desc>
  <doc>JEP-xxxx</doc>
</header>

<header>
  <name>Stop</name>
  <desc>The dateTime at which a state, event, or activity stops</desc>
  <doc>JEP-xxxx</doc>
</header>
    

9. XML Schema

Not applicable.


Notes

1. JEP-0119: Extended Presence Protocol Suite <http://www.jabber.org/jeps/jep-0119.html>.

2. JEP-0131: Stanza Headers and Internet Metadata (SHIM) <http://www.jabber.org/jeps/jep-0131.html>.

3. JEP-0082: Jabber Date and Time Profiles <http://www.jabber.org/jeps/jep-0082.html>.

4. RFC 3921: Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence <http://www.ietf.org/rfc/rfc3921.txt>.

5. JEP-0107: User Mood <http://www.jabber.org/jeps/jep-0107.html>.

6. JEP-0108: User Activity <http://www.jabber.org/jeps/jep-0108.html>.

7. draft-ietf-simple-rpid <http://www.ietf.org/internet-drafts/draft-ietf-simple-rpid-09.txt>. Work in progress.

8. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

9. The Jabber Registrar maintains a list of reserved Jabber protocol namespaces as well as registries of parameters used in the context of protocols approved by the Jabber Software Foundation. For further information, see <http://www.jabber.org/registrar/>.


Revision History

Version 0.1 (2005-04-21)

Initial JEP version. (psa)

Version 0.0.2 (2005-04-07)

Modified to use SHIM headers rather than a structured data format qualified by a dedicated namespace. (psa)

Version 0.0.1 (2005-03-17)

First draft. (psa)


END