XEP-0080: User Location

NOTICE: The protocol defined herein is a Draft Standard of the XMPP Standards Foundation. Implementations are encouraged and the protocol is appropriate for deployment in production systems, but some changes to the protocol are possible before it becomes a Final Standard.

Table of Contents

1. Introduction

This document defines a format for capturing data about an entity's geographical location (geoloc). The format defined herein can describe most earthbound geographical locations, especially locations that may change fairly frequently. Potential uses for this approach include:

• Publishing location information to a set of subscribers.
• Querying another entity for its location.
• Sending location information to another entity.
• Attaching location information to presence.

Geographical location is captured in terms of Global Positioning System (GPS) coordinates as well as civil location (city, street, building, etc.).

2. Requirements

The format defined herein was designed to address the following requirements:

• It shall be possible to encapsulate location in terms of Global Positioning System (GPS) coordinates as well as civil location (city, street, building, etc.).
• The GPS encoding mechanism shall have a single set of units, so that receivers do not need to use heuristics to determine an entity's position.
• It shall be possible to specify the known amount of error in the GPS coordinates.
• It shall be possible to include a natural-language description of the location.

3. Data Format

Information about the entity's location is provided by the entity and propagated on the network by the entity's associated application (usually a client). The information is structured by means of a <geoloc/> element that is qualified by the 'http://jabber.org/protocol/geoloc' namespace; the location information itself is provided as the XML character data of the following child elements:

NOTE: The datatypes specified above are defined in XML Schema Part 2 [4].

4. Recommended Transport

Location information about human users SHOULD be communicated and transported by means of Publish-Subscribe (XEP-0060) [5] or the subset thereof specified in Personal Eventing Protocol (XEP-0163) [6] (the examples below assume that the user's XMPP server supports PEP, thus the publish request lacks a 'to' address and the notification message has a 'from' address of the user's bare JID).

Although the XMPP publish-subscribe extension is the preferred means for transporting location information about human users, applications that do not involve human users (e.g., device tracking) MAY use other transport methods; however, because location information is not pure presence information and can change independently of network availability, it SHOULD NOT be provided as an extension to <presence/>.

<iq type='set' from='portia@merchantofvenice.lit/pda' id='publish1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='http://jabber.org/protocol/geoloc'>
      <item>
        <geoloc xmlns='http://jabber.org/protocol/geoloc' xml:lang='en'>
          <accuracy>20</accuracy>
          <country>Italy</country>
          <lat>45.44</lat>
          <locality>Venice</locality>
          <lon>12.33</lon>
        </geoloc>
      </item>
    </publish>
  </pubsub>
</iq>
    

<message from='portia@merchantofvenice.lit' 
         to='bassanio@merchantofvenice.lit'>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='http://jabber.org/protocol/geoloc'>
      <item id='d81a52b8-0f9c-11dc-9bc8-001143d5d5db'>
        <geoloc xmlns='http://jabber.org/protocol/geoloc' xml:lang='en'>
          <accuracy>20</accuracy>
          <country>Italy</country>
          <lat>45.44</lat>
          <locality>Venice</locality>
          <lon>12.33</lon>
        </geoloc>
      </item>
    </items>
  </event>
</message>
    

<iq from='portia@merchantofvenice.lit/pda' 
    id='publish2'
    type='set'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='http://jabber.org/protocol/geoloc'>
      <item>
        <geoloc xmlns='http://jabber.org/protocol/geoloc'/>
      </item>
    </publish>
  </pubsub>
</iq>
    

<message from='portia@merchantofvenice.lit' 
         to='bassanio@merchantofvenice.lit'>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='http://jabber.org/protocol/geoloc'>
      <item id='d81a52b8-0f9c-11dc-9bc8-001143d5d5db'>
        <geoloc xmlns='http://jabber.org/protocol/geoloc'/>
      </item>
    </items>
  </event>
</message>
    

5. Implementation Notes

Avoid "Mars probe" issues: as specified in Table 1, the units for <lat/> and <lon/> MUST be decimal degrees (where South and West are negative, North and East are positive), the units for <alt/> MUST be meters above or below sea level, and the units for <accuracy/> MUST be meters. [7]

In applications where updates are sent whenever there is a certain distance change in location, those applications SHOULD account for time as well, to avoid rate-limiting when the user is (for example) on a jet plane. One possible way to do this would be to send updates at most once per minute of time (every time 60 seconds have elapsed).

Inferences SHOULD NOT be made about accuracy from the number of digits specified in the location or altitude.

Why the datum madness? See <http://www.xmpp.org/extensions/gps_datum.html> for an example.

An entity can provide a GPS path by publishing a series of items (i.e., multiple pubsub events) with appropriate values of the <timestamp/> element.

6. Mapping to Other Formats

There are many XML data formats for physical location or address information. It is beyond the scope of this document to provide a mapping from the extension defined herein to every such format. However, it would be valuable to provide a mapping from the XMPP format to the formats used in other presence or extended presence protocols. The two main protocols of interest are:

1. The Wireless Village (now "IMPS") specifications for mobile instant messaging; these specifications define a presence attribute for address information as encapsulated in the IMPS "Address" element [8].

2. The SIP-based SIMPLE specifications; in particular, the IETF's GEOPRIV Working Group has defined an extension to the IETF's Presence Information Data Format (PIDF) [9] for location information, as specified in RFC 4119 [10] (also known as "PIDF-LO").

The following table also maps the format defined herein to the vCard XML format specified in vcard-temp (XEP-0054) [11].

7. Internationalization Considerations

Because the character data contained in <geoloc/> child elements of type 'xs:string' is intended to be readable by humans, the <geoloc/> element SHOULD possess an 'xml:lang' attribute specifying the natural language of such character data.

8. Security Considerations

It is imperative to control access to location information, at least by default. Imagine that a stalker got unauthorized access to this information, with enough accuracy and timeliness to be able to find the target person. This scenario could lead to loss of life, so please take access control checks seriously. If an error is deliberately added to a location, the error SHOULD be the same for all receivers, to minimize the likelihood of triangulation. In the case of deliberate error, the <accuracy/> element SHOULD NOT be included.

9. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [17].

10. XMPP Registrar Considerations

11. XML Schema

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

<xs:schema 
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://jabber.org/protocol/geoloc' 
    xmlns='http://jabber.org/protocol/geoloc'
    elementFormDefault='qualified'>

  <xs:annotation>
    <xs:documentation>
      The protocol documented by this schema is defined in
      XEP-0080: http://www.xmpp.org/extensions/xep-0080.html
    </xs:documentation>
  </xs:annotation>

  <xs:element name='geoloc'>
    <xs:complexType>
      <xs:sequence minOccurs='0'>
        <xs:element name='accuracy' minOccurs='0' type='xs:decimal'/>
        <xs:element name='alt' minOccurs='0' type='xs:decimal'/>
        <xs:element name='area' minOccurs='0' type='xs:string'/>
        <xs:element name='bearing' minOccurs='0' type='xs:decimal'/>
        <xs:element name='building' minOccurs='0' type='xs:string'/>
        <xs:element name='country' minOccurs='0' type='xs:string'/>
        <xs:element name='countrycode' minOccurs='0' type='xs:string'/>
        <xs:element name='datum' minOccurs='0' type='xs:string'/>
        <xs:element name='description' minOccurs='0' type='xs:string'/>
        <xs:element name='error' minOccurs='0' type='xs:decimal'/>
        <xs:element name='floor' minOccurs='0' type='xs:string'/>
        <xs:element name='lat' minOccurs='0' type='xs:decimal'/>
        <xs:element name='locality' minOccurs='0' type='xs:string'/>
        <xs:element name='lon' minOccurs='0' type='xs:decimal'/>
        <xs:element name='postalcode' minOccurs='0' type='xs:string'/>
        <xs:element name='region' minOccurs='0' type='xs:string'/>
        <xs:element name='room' minOccurs='0' type='xs:string'/>
        <xs:element name='speed' minOccurs='0' type='xs:decimal'/>
        <xs:element name='street' minOccurs='0' type='xs:string'/>
        <xs:element name='text' minOccurs='0' type='xs:string'/>
        <xs:element name='timestamp' minOccurs='0' type='xs:dateTime'/>
        <xs:element name='uri' minOccurs='0' type='xs:anyURI'/>
      </xs:sequence>
      <xs:attribute ref='xml:lang' use='optional'/>
    </xs:complexType>
  </xs:element>

</xs:schema>
  

Appendices

Appendix A: Document Information

Series: XEP
Number: 0080
Publisher: XMPP Standards Foundation
Status: Draft
Type: Standards Track
Version: 1.7
Last Updated: 2009-09-15
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0163
Supersedes: None
Superseded By: None
Short Name: geoloc
Schema: <http://www.xmpp.org/schemas/geoloc.xsd>
Source Control: HTML
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 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

Appendix H: Revision History

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

END