Dynamic Extensions to the Presence Information Data Format Location Object (PIDF-LO)
RFC 5962

Internet Engineering Task Force (IETF)                    H. Schulzrinne
Request for Comments: 5962                                      V. Singh
Category: Standards Track                            Columbia University
ISSN: 2070-1721                                            H. Tschofenig
                                                  Nokia Siemens Networks
                                                              M. Thomson
                                                      Andrew Corporation
                                                          September 2010

       Dynamic Extensions to the Presence Information Data Format
                       Location Object (PIDF-LO)

Abstract

   The Geopriv Location Object introduced by the Presence Information
   Data Format - Location Object (PIDF-LO), RFC 4119, defines a basic
   XML format for carrying geographical information of a presentity.
   This document defines PIDF-LO extensions to convey information about
   moving objects.  Elements are defined that enable expression of
   spatial orientation, speed, and heading of the presentity.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5962.

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Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Dynamic Elements ................................................3
      3.1. Angular Measures and Coordinate Reference Systems ..........5
   4. Dynamic Feature XML Schema ......................................6
   5. Security Considerations .........................................7
   6. IANA Considerations .............................................7
      6.1. Dynamic Feature Extensions Namespace Registration ..........7
      6.2. Dynamic Feature Extensions Schema Registration .............8
   7. Acknowledgements ................................................8
   8. References ......................................................9
      8.1. Normative References .......................................9
      8.2. Informative References .....................................9
   Appendix A.  Earth Centered, Earth Fixed Direction Vectors ........10

1.  Introduction

   The Presence Information Data Format - Location Object (PIDF-LO) (see
   RFC 4119 [RFC4119]) provides geographical location of a presentity.
   This corresponds to a physical location at a given instance of time.
   RFC 5491 [RFC5491] extends PIDF-LO and provides additional guidelines
   to implementers.

   This document extends PIDF-LO to convey spatial orientation, speed,
   and heading of a presentity.  The addition of rate-of-change
   information to the PIDF-LO enables a range of use cases.  These use
   cases either use dynamic information directly or use that information

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   for smoother tracking of a position over time.  For example, an
   application that continuously tracks a presentity could use velocity
   information to extrapolate positions in between times that location
   information is measured.  A shipping company could directly use speed
   to monitor delivery truck speed to ensure speed limits are observed.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in RFC 2119
   [RFC2119].

   This document uses the term "presentity", as defined in RFC 2778
   [RFC2778], to refer to the device subject to location determination.
   The similarity to presence concepts and the abstract location privacy
   architecture, as described in RFC 4079 [RFC4079], led to re-use of
   the Presence Information Data Format (PIDF) (see RFC 3863 [RFC3863]),
   and its enhancement for location information (see RFC 4119
   [RFC4119]).  Note that this document does not differentiate between
   human and non-human objects, and hence both are in scope.

3.  Dynamic Elements

   This document defines a new element, <Dynamic>, for the conveyance of
   dynamic information.

   Dynamic information MAY be included without any other location
   information being present.  When dynamic information is associated
   with information about the instantaneous position of the presentity,
   the <Dynamic> element MUST be included in the same <location-info>
   element as the corresponding geodetic (or civic) location
   information.

   Dynamic information can be safely ignored by a recipient that does
   not support this specification.  The <Dynamic> element contains the
   following components:

   orientation:

      The <orientation> element describes the spatial orientation of the
      presentity -- the direction that the object is pointing.  For a
      device, this orientation might depend on the type of device.  See
      Section 3.1 for details.

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   speed:

      Speed is the time rate of change in position of a presentity
      without regard for direction: the scalar component of velocity.
      The value for the <speed> element is a measure that is defined in
      meters per second.

   heading:

      Heading is the directional component of velocity.  See Section 3.1
      for details.

   Each element can be omitted if no information is available.  In the
   following example, the presentity is approximately oriented to the
   North at a slightly elevated angle.  The presentity is travelling
   24 meters per second to the West:

   <?xml version="1.0" encoding="UTF-8"?>
   <presence
       xmlns="urn:ietf:params:xml:ns:pidf"
       xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
       xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
       xmlns:dyn="urn:ietf:params:xml:ns:pidf:geopriv10:dynamic"
       xmlns:gml="http://www.opengis.net/gml"
       entity="pres:alice@example.com">
       <dm:device id="abc123">
           <gp:geopriv>
               <gp:location-info>
                   <dyn:Dynamic>
                       <dyn:orientation>-3 12</dyn:orientation>
                       <dyn:speed>24</dyn:speed>
                       <dyn:heading>278</dyn:heading>
                   </dyn:Dynamic>
               </gp:location-info>
               <gp:usage-rules/>
               <method>gps</method>
           </gp:geopriv>
           <timestamp>2009-06-22T20:57:29Z</timestamp>
           <dm:deviceID>mac:1234567890ab</dm:deviceID>
       </dm:device>
   </presence>

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   Another example shows a PIDF-LO document of the presentity
   alice@example.com on a bike travelling 12 meters per second.  Her
   position is indicated as a circle.  The values for speed may be used
   by a receiver to adjust the uncertainty over time.

   <?xml version="1.0" encoding="UTF-8"?>
   <presence
       xmlns="urn:ietf:params:xml:ns:pidf"
       xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
       xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
       xmlns:dyn="urn:ietf:params:xml:ns:pidf:geopriv10:dynamic"
       xmlns:gml="http://www.opengis.net/gml"
       xmlns:gs="http://www.opengis.net/pidflo/1.0"
       entity="pres:alice@example.com">
       <dm:device id="abc123">
           <gp:geopriv>
               <gp:location-info>
                   <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326">
                       <gml:pos>42.5463 -73.2512</gml:pos>
                       <gs:radius uom="urn:ogc:def:uom:EPSG::9001">
                           100
                       </gs:radius>
                   </gs:Circle>
                   <dyn:Dynamic>
                       <dyn:speed>12</dyn:speed>
                   </dyn:Dynamic>
               </gp:location-info>
               <gp:usage-rules/>
               <method>gps</method>
           </gp:geopriv>
           <timestamp>2009-06-22T20:57:29Z</timestamp>
           <dm:deviceID>mac:1234567890ab</dm:deviceID>
       </dm:device>
   </presence>

3.1.  Angular Measures and Coordinate Reference Systems

   [RFC5491] constrains the coordinate reference system (CRS) used in
   PIDF-LO to World Geodetic System 1984 (WGS 84), using either the two-
   dimensional (latitude, longitude) CRS identified by
   "urn:ogc:def:crs:EPSG::4326" or the three-dimensional (latitude,
   longitude, altitude) CRS identified by "urn:ogc:def:crs:EPSG::4979".
   Dynamic locations similarly assume that either of these coordinate
   reference systems will be used.

   The <orientation> and <heading> elements both describe a direction.
   The <orientation> element describes the "direction of facing"; the
   <heading> element describes the "direction of travel".  Both measures

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   contain one or two angular values that are expressed relative to the
   current position of the presentity (see Appendix A).  Angular
   measures are expressed in degrees, and values can be negative.  If
   two measures are present, the values MUST be separated by whitespace.

   The first measure specifies the horizontal direction from the current
   position of the presentity to a point that it is pointing towards
   (for <orientation>) or travelling towards (for <heading>).
   Horizontal angles are measured from Northing to Easting.  Horizontal
   angles start from zero when pointing to or travelling towards the
   North and increase towards the East.

   The second measure, if present, specifies the vertical component of
   this angle.  This angle is the elevation from the local horizontal
   plane.  If the second angle value is omitted, the vertical component
   is unknown.  If only one angle is present, <orientation> describes
   only the horizontal component.  For <heading>, the associated <speed>
   measure contains only the horizontal component of speed.

4.  Dynamic Feature XML Schema

   <?xml version="1.0"?>
   <xs:schema
       targetNamespace="urn:ietf:params:xml:ns:pidf:geopriv10:dynamic"
       xmlns:dyn="urn:ietf:params:xml:ns:pidf:geopriv10:dynamic"
       xmlns:xs="http://www.w3.org/2001/XMLSchema"
       elementFormDefault="qualified"
       attributeFormDefault="unqualified">

     <xs:element name="Dynamic" type="dyn:dynamicType"/>

     <xs:complexType name="dynamicType">
       <xs:complexContent>
         <xs:restriction base="xs:anyType">
           <xs:sequence>
             <xs:element name="orientation" minOccurs="0"
                         type="dyn:directionType"/>
             <xs:element name="speed" minOccurs="0"
                         type="xs:double"/>
             <xs:element name="heading" minOccurs="0"
                         type="dyn:directionType"/>
             <xs:any namespace="##other" processContents="lax"
                     minOccurs="0" maxOccurs="unbounded"/>
           </xs:sequence>
           <xs:anyAttribute namespace="##other" processContents="lax"/>
         </xs:restriction>
       </xs:complexContent>
     </xs:complexType>

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     <xs:simpleType name="directionType">
       <xs:restriction base="dyn:doubleListType">
         <xs:minLength value="1"/>
         <xs:maxLength value="2"/>
       </xs:restriction>
     </xs:simpleType>

     <xs:simpleType name="doubleListType">
       <xs:list itemType="xs:double"/>
     </xs:simpleType>

   </xs:schema>

5.  Security Considerations

   This document defines additional location elements carried by
   PIDF-LO.  These additional elements provide greater reason to observe
   the privacy and security considerations described in RFC 4119
   [RFC4119].  No further privacy or security measures are necessary.

   RFC 4119 points back to RFC 3694 [RFC3694] and RFC 3693 [RFC3693] to
   describe the threat model and the security requirements imposed on
   the GEOPRIV architecture for sharing location information as a result
   of the threat model.  It is important to note that these two
   documents often refer to threats related to the current location
   information of a presentity, while this document introduces dynamic
   information that may be used by attackers to anticipate the future
   location of a presentity.  While already a series of location
   snapshots is likely to offer information for guessing the future
   location of a presentity, it has to be said that including more
   information in a PIDF-LO does increase the severity of an information
   leak.  Those who deploy location-based services are in general
   strongly advised to provide their users with ways to control the
   distribution of location information to those who have been
   authorized to see it.

6.  IANA Considerations

   This section registers a new XML namespace (as described in
   [RFC3688]) and a new XML schema.

6.1.  Dynamic Feature Extensions Namespace Registration

   URI: urn:ietf:params:xml:ns:pidf:geopriv10:dynamic

   Registrant Contact: IETF Geopriv Working Group, Hannes Tschofenig
      (hannes.tschofenig@gmx.net).

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   XML:

      BEGIN
      <?xml version="1.0"?>
      <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
        "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
      <html xmlns="http://www.w3.org/1999/xhtml">
      <head>
        <title>Dynamic Feature Extensions Namespace</title>
      </head>
      <body>
        <h1>Namespace for Dynamic Feature Extensions to PIDF-LO</h1>
        <h2>urn:ietf:params:xml:ns:pidf:geopriv10:dynamic</h2>
      <p>See <a href=
        "http://www.rfc-editor.org/rfc/rfc5962.txt"> RFC5962</a>.</p>
      </body>
      </html>
      END

6.2.  Dynamic Feature Extensions Schema Registration

   URI: urn:ietf:params:xml:schema:pidf:dynamic

   Registrant Contact: IETF Geopriv Working Group, Hannes Tschofenig
      (hannes.tschofenig@gmx.net)

   XML: The XML schema registered is contained in Section 4.  Its first
      line is

   <?xml version="1.0"?>

   and its last line is

   </xs:schema>

7.  Acknowledgements

   We would like to thank Klaus Darilion, Cullen Jennings, Rohan Mahy,
   Carl Reed, and Brian Rosen for their comments.  Furthermore, we would
   like to thank Alexey Melnikov, Adrian Farrel, Tim Polk, Dan Romascanu
   for his IESG review comments, Avshalom Houri for his GenArt review,
   Hilarie Orman for her SECDIR review, and Joel Jaeggli for his
   Operations Directorate review.

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8.  References

8.1.  Normative References

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3688]   Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
               January 2004.

   [RFC4119]   Peterson, J., "A Presence-based GEOPRIV Location Object
               Format", RFC 4119, December 2005.

8.2.  Informative References

   [RFC2778]   Day, M., Rosenberg, J., and H. Sugano, "A Model for
               Presence and Instant Messaging", RFC 2778, February 2000.

   [RFC3693]   Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
               J. Polk, "Geopriv Requirements", RFC 3693, February 2004.

   [RFC3694]   Danley, M., Mulligan, D., Morris, J., and J. Peterson,
               "Threat Analysis of the Geopriv Protocol", RFC 3694,
               February 2004.

   [RFC3863]   Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr,
               W., and J. Peterson, "Presence Information Data Format
               (PIDF)", RFC 3863, August 2004.

   [RFC4079]   Peterson, J., "A Presence Architecture for the
               Distribution of GEOPRIV Location Objects", RFC 4079,
               July 2005.

   [RFC5491]   Winterbottom, J., Thomson, M., and H. Tschofenig,
               "GEOPRIV Presence Information Data Format Location Object
               (PIDF-LO) Usage Clarification, Considerations, and
               Recommendations", RFC 5491, March 2009.

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Appendix A.  Earth Centered, Earth Fixed Direction Vectors

   The absolute orientation or heading of a presentity depends on its
   latitude and longitude.  The following vectors can be used to
   determine the absolute direction in the WGS 84 Earth Centered, Earth
   Fixed (X, Y, Z) coordinate space.

   The direction of North as a unit vector in Earth Centered, Earth
   Fixed (ECEF) coordinates is:

      North = [ -1 * sin(latitude) * cos(longitude),
                -1 * sin(latitude) * sin(longitude),
                cos(latitude) ]

   The direction of "up" (the upward normal of the horizontal plane) as
   a unit vector in ECEF coordinates is:

      Up = [ cos(latitude) * cos(longitude),
             cos(latitude) * sin(longitude),
             sin(latitude) ]

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Authors' Addresses

   Henning Schulzrinne
   Columbia University
   Department of Computer Science
   450 Computer Science Building
   New York, NY  10027
   US

   Phone: +1 212 939 7004
   EMail: hgs@cs.columbia.edu
   URI:   http://www.cs.columbia.edu/

   Vishal Singh
   Columbia University
   Department of Computer Science
   450 Computer Science Building
   New York, NY  10027
   US

   EMail: vs2140@cs.columbia.edu
   URI:   http://www.cs.columbia.edu/~vs2140

   Hannes Tschofenig
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  02600
   Finland

   Phone: +358 (50) 4871445
   EMail: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at/

   Martin Thomson
   Andrew Corporation
   Wollongong
   NSW Australia

   EMail: martin.thomson@andrew.com

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