XEP-0149: Time Periods

NOTICE: This Informational specification defines a best practice or protocol profile that has been approved by the XMPP Council and/or the XSF Board of Directors. Implementations are encouraged and the best practice or protocol profile is appropriate for deployment in production systems.

Table of Contents

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 various forms of "extended presence" (see Extended Presence Protocol Suite [1]).

This document 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 [2].

2. Requirements

This document addresses the following requirements:

1. Provide the ability to specify time periods for states, events, and activities communicated via Jabber/XMPP protocols.
2. Conform to XMPP 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 XEP-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

<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>
    

<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>
    

<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>
    

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 'from' and 'until' attributes specified in RFC 4480 [7], see also RFC 4481 [8]).

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 document requires no interaction with the Internet Assigned Numbers Authority (IANA) [9].

8. XMPP Registrar Considerations

<header>
  <name>Start</name>
  <desc>The dateTime at which a state, event, or activity starts</desc>
  <doc>XEP-0149</doc>
</header>

<header>
  <name>Stop</name>
  <desc>The dateTime at which a state, event, or activity stops</desc>
  <doc>XEP-0149</doc>
</header>
    

Appendices

Appendix A: Document Information

Series: XEP
Number: 0149
Publisher: XMPP Standards Foundation
Status: Active
Type: Informational
Version: 1.0
Last Updated: 2006-01-24
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0082
Supersedes: None
Superseded By: None
Short Name: N/A
Source Control: HTML  RSS
This document in other formats: XML  PDF

Appendix B: Author Information

Appendix C: Legal Notices

Appendix D: 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 XMPP Standards 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 document 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.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.

Errata can be sent to <editor@xmpp.org>.

Appendix F: Requirements Conformance

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

Appendix G: Notes

Appendix H: Revision History

Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/

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