This document defines a method to specify the valid time periods for states, events, and activities communicated via Jabber/XMPP protocols.
NOTICE: This JEP is currently within Last Call or under consideration by the Jabber Council for advancement to the next stage in the JSF standards process. For further details, visit <http://www.jabber.org/council/queue.shtml>.
Status: Proposed
Type: Informational
Number: 0149
Version: 0.2
Last Updated: 2005-12-21
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Superseded By: None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)>
Email: stpeter@jabber.org
JID: stpeter@jabber.org
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/>).
The preferred venue for discussion of this document is the Standards-JIG discussion list: <http://mail.jabber.org/mailman/listinfo/standards-jig>.
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.
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.
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 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].
This JEP addresses the following requirements:
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:
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.
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>
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'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>
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.
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 draft-ietf-simple-rpid [7]).
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.
This JEP requires no interaction with the Internet Assigned Numbers Authority (IANA) [8].
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>
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-10.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/>.
END