Internet Engineering Task Force (IETF) H. Schulzrinne

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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RFC 5962 Dynamic Extensions to PIDF-LO September 2010

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:[email protected]">
<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
[email protected] 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:[email protected]">
<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
([email protected]).

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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
([email protected])

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: [email protected]
URI: http://www.cs.columbia.edu/

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

EMail: [email protected]
URI: http://www.cs.columbia.edu/~vs2140

Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland

Phone: +358 (50) 4871445
EMail: [email protected]
URI: http://www.tschofenig.priv.at/

Martin Thomson
Andrew Corporation
Wollongong
NSW Australia

EMail: [email protected]

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