XEP-xxxx: User Time Zone

Abstract:This specification defines a payload format for communicating information about a user's time zone. The payload format is typically transported using the personal eventing protocol, a profile of XMPP publish-subscribe specified in XEP-0163.
Author:Lance Stout
Copyright:© 1999 - 2013 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status:ProtoXEP
Type:Standards Track
Version:0.1
Last Updated:2013-10-28

WARNING: This document has not yet been accepted for consideration or approved in any official manner by the XMPP Standards Foundation, and this document is not yet an XMPP Extension Protocol (XEP). If this document is accepted as a XEP by the XMPP Council, it will be published at <http://xmpp.org/extensions/> and announced on the <standards@xmpp.org> mailing list.


Table of Contents


1. Introduction
2. Protocol
    2.1. TZO Element
    2.2. Transport Mechanism
3. Security Considerations
4. IANA Considerations
5. XMPP Registrar Considerations
    5.1. Protocol Namespaces
    5.2. Protocol Versioning
6. XML Schema

Appendices
    A: Document Information
    B: Author Information
    C: Legal Notices
    D: Relation to XMPP
    E: Discussion Venue
    F: Requirements Conformance
    G: Notes
    H: Revision History


1. Introduction

Publish-Subscribe (XEP-0060) [1] and Personal Eventing Protocol (XEP-0163) [2] can be used to publish a wide variety of "extended presence" information about users. This document specifies an extended presence payload format that communicates information about a user's time zone. For example, this information may be of interest to a user's contacts for displaying notices advising against starting a chat at 4am in the user's local time.

Time zone information can also be obtained through Entity Time (XEP-0202) [3] by directly querying a full JID for a user. However, given that some clients are chiefly concerned with the time zone offset, and in the interest of reducing floods of IQ requests, we define a way to expose the time zone offset via PEP.

2. Protocol

2.1 TZO Element

The numeric time zone offset from UTC for the user is expressed as the textual content of the <tzo/> element qualified by the 'urn:xmpp:timezone:0' namespace. [4] The format MUST conform to the Time Zone Definition (TZD) specified in XMPP Date and Time Profiles (XEP-0082) [6].

2.2 Transport Mechanism

When a user wishes to share time zone information, its client may publish that fact to a PEP node whose NodeID is "urn:xmpp:timezone:0" (see Protocol Namespaces regarding issuance of one or more permanent namespaces). Because time zone information is not pure presence information and can change independently of the user's availability, it SHOULD NOT be provided as an extension to the <presence/> stanza type.

Example 1. User Publishes Time Zone Offset

<iq type='set' from='juliet@capulet.example/balcony' id='tzo1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:timezone:0'>
      <item>
        <tzo xmlns='urn:xmpp:timezone:0'>-07:00</tzo>
      </item>
    </publish>
  </pubsub>
</iq>
    

The time zone offset is then delivered to all subscribers:

Example 2. Time Zone Offset is Delivered to All Subscribers

<message from='juliet@capulet.example' to='romeo@montague.example'>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='urn:xmpp:timezone:0'>
      <item id='1feea9cceec2537e1b561e66d45bc566e276f22f'>
        <tzo xmlns='urn:xmpp:timezone:0'>-07:00</tzo>
      </item>
    </items>
  </event>
</message>
    

When the user wishes to stop broadcasting its time zone offset, the user's client SHOULD send an empty <tzo/> element with the same ItemID:

Example 3. User Publishes Stop Information

<iq type='set' from='juliet@capulet.example/balcony' id='tzo2'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:timezone:0'>
      <item id='1feea9cceec2537e1b561e66d45bc566e276f22f'>
        <tzo xmlns='urn:xmpp:timezone:0'/>
      </item>
    </publish>
  </pubsub>
</iq>
    

Example 4. Stop Information is Delivered to All Subscribers

<message from='juliet@capulet.example' to='romeo@montague.example'>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='urn:xmpp:timezone:0'>
      <item id='1feea9cceec2537e1b561e66d45bc566e276f22f'>
        <tzo xmlns='urn:xmpp:timezone:0'/>
      </item>
    </items>
  </event>
</message>
    

3. Security Considerations

Revealing an entity's numeric time zone offset may leak limited information about the entity's current location. If the entity's understanding of UTC is far off from actual UTC, revealing that discrepancy may make it possible for an attacker to send XML stanzas that appear to be in the past or future even though they are not; therefore an entity should use the Network Time Protocol (RFC 958 [7]) or a similar technology to stay synchronized with actual UTC.

4. IANA Considerations

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

5. XMPP Registrar Considerations

5.1 Protocol Namespaces

The XMPP Registrar [9] includes 'urn:xmpp:timezone:0' in its registry of protocol namespaces (see <http://xmpp.org/registrar/namespaces.html>).

5.2 Protocol Versioning

If the protocol defined in this specification undergoes a revision that is not fully backwards-compatible with an older version, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.

6. XML Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='urn:xmpp:timezone:0'
    xmlns='urn:xmpp:timezone:0'
    elementFormDefault='qualified'>

  <xs:annotation>
    <xs:documentation>
      The protocol documented by this schema is defined in
      XEP-xxxx: http://www.xmpp.org/extensions/xep-xxxx.html
    </xs:documentation>
  </xs:annotation>

  <xs:element name='tzo' type='xs:string'/>

</xs:schema>
  

Appendices


Appendix A: Document Information

Series: XEP
Number: xxxx
Publisher: XMPP Standards Foundation
Status: ProtoXEP
Type: Standards Track
Version: 0.1
Last Updated: 2013-10-28
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0082, XEP-0163
Supersedes: None
Superseded By: None
Short Name: NOT_YET_ASSIGNED
This document in other formats: XML  PDF


Appendix B: Author Information

Lance Stout

Email: lance@lance.im
JabberID: lance@lance.im


Appendix C: Legal Notices

Copyright

This XMPP Extension Protocol is copyright © 1999 - 2013 by the XMPP Standards Foundation (XSF).

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <http://xmpp.org/about-xmpp/xsf/xsf-ipr-policy/> or obtained by writing to XMPP Standards Foundation, 1899 Wynkoop Street, Suite 600, Denver, CO 80202 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) 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

1. XEP-0060: Publish-Subscribe <http://xmpp.org/extensions/xep-0060.html>.

2. XEP-0163: Personal Eventing Protocol <http://xmpp.org/extensions/xep-0163.html>.

3. XEP-0202: Entity Time <http://xmpp.org/extensions/xep-0202.html>.

4. While Entity Time (XEP-0202) [5] defines its own <tzo/> element, the schema allows for neither its reuse as a standalone element nor for the use of the <time/> element without a <utc/> element.

5. XEP-0202: Entity Time <http://xmpp.org/extensions/xep-0202.html>.

6. XEP-0082: XMPP Date and Time Profiles <http://xmpp.org/extensions/xep-0082.html>.

7. RFC 958: Network Time Protocol (NTP) <http://tools.ietf.org/html/rfc0958>.

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 XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://xmpp.org/registrar/>.


Appendix H: Revision History

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

Version 0.1 (2013-10-28)

Initial version.

(lance)

END