Dynamic Feature Extensions to the Presence Information Data Format Location Object (PIDF-LO)
draft-singh-geopriv-pidf-lo-dynamic-04.txt

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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. The PIDF-LO specification made a subset of the functionality offered by the Geography Markup Language (GML) standard 3.0 mandatory to implement. This document defines child elements to the <location-info> element specified in RFC 4119 to carry temporal feature elements useful for tracking moving objects. It defines five elements, namely speed, bearing, acceleration elevation and directionOfObject.

Table of Contents

1.  Introduction
2.  Terminology
3.  XML Extensions
4.  XML Schema
5.  Example
6.  Security Considerations
7.  IANA Considerations
8.  Acknowledgements
9.  References
    9.1.  Normative References
    9.2.  Informative References
Appendix A.  Transferring Multiple Location Objects within SIP
§  Authors' Addresses
§  Intellectual Property and Copyright Statements

1.  Introduction

The Presence Information Data Format - Location Object (PIDF-LO) (see RFC 4119 [RFC4119] (Peterson, J., “A Presence-based GEOPRIV Location Object Format,” December 2005.)) provides geographical location of the presentity. This corresponds to a physical location at a given instance of time. The PIDF-LO specification made a subset of the functionality offered by the Geography Markup Language (GML) standard 3.0 mandatory to implement. With the extensions defined in [I‑D.ietf‑geopriv‑pdif‑lo‑profile] (Winterbottom, J., Thomson, M., and H. Tschofenig, “GEOPRIV PIDF-LO Usage Clarification, Considerations and Recommendations,” November 2008.) more guidelines to implementers are being provided with respect to a number of location shapes that have to be supported for usage within PIDF-LO. However, a number of applications benefit from having access to information about changes in location. Location change information is likely to be useful for logistics and public safety. For example, shipping companies or dispatch centers can use it to track whether vehicles are deviating from an established path or exceeding speed limits.

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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

3.  XML Extensions

This document defines a location vector by adding child elements to the <location-info> element described in RFC 4119 [RFC4119] (Peterson, J., “A Presence-based GEOPRIV Location Object Format,” December 2005.), to carry temporal feature elements. A receiver MAY ignore the temporal elements defined in this document if it does not understand this extension.

speed:

Speed is the rate of motion. (The terms speed and velocity are often used interchangeably, but speed is a scalar, having magnitude only, while velocity is a vector, having both magnitude and direction.)

This element contains a 'uom' (Units Of Measure) attribute, which is a reference to a reference system for the amount. The 'uom' attribute uses a URI to refer to a unit of measure definition. The GML document defines a set of convenience measure types and a further explaination is provided at the end of this section.

bearing:

Bearing is defined as the horizontal direction of one terrestrial point from another, expressed as the angular distance from a reference direction. It is usually measured from 000 degrees at the reference direction clockwise through 360 degrees.

The <bearing> element is of type gml:DirectionPropertyType and contains a gml:DirectionVector, gml:CompassPoint, DirectionKeyword, or a DirectionString element. This document profiles the usage of this GML element and mandates applications using this document to make use of the <DirectionVector> element only.

acceleration:

This element specifies the rate (usually rapid) at which something happens. The <acceleration> element also contains a 'uom' attribute.

directionOfObject:

The <directionOfObject> describes the instantaneous horizontal of the front of the object relative to true north and the vertical angle relative to the earth's spheroid. It uses the GML <directionVector> element.

GML permits a range of units of measure for the uom attribute. This document restricts this set to the #m/s (meters per second).

4.  XML Schema

This document does not define a new schema but instead re-uses a subset of the dynamicFeature.xsd schema available with GML 3.1.1, namely <speed>, <bearing>, <acceleration>, and <directionOfObject>.

These four elements are conveyed inside the <location-info> element defined by RFC 4119 [RFC4119] (Peterson, J., “A Presence-based GEOPRIV Location Object Format,” December 2005.).

5.  Example

The following example shows a PIDF-LO document indicating geospatial location information using the gml:Point structure. Following the <gml:location> element the additional fields releated to temporal characteristics are included.

<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
  xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
  xmlns:gml="http://www.opengis.net/gml"
  entity="pres:geotarget@example.com">

  <device id="sg89ae">
      <gp:geopriv>
        <gp:location-info>
          <gml:location>
            <gml:Point srsName="urn:ogc:def:crs:EPSG::4326">
              <gml:pos>-34.407 150.883</gml:pos>
            </gml:Point>
          </gml:location>
          <gml:speed uom="#m/s">12</gml:speed>
          <gml:bearing>
            <gml:DirectionVector>
              <gml:vector> 270.0 -60.0</gml:vector>
            </gml:DirectionVector>
          </gml:bearing>
        </gp:location-info>
        <gp:usage-rules>
          <gp:retransmission-allowed>no</gp:retransmission-allowed>
          <gp:retention-expiry>2003-06-23T04:57:29Z
          </gp:retention-expiry>
        </gp:usage-rules>
      </gp:geopriv>
    <timestamp>2008-06-22T20:57:29Z</timestamp>
  </device>

</presence>

6.  Security Considerations

This document defines additional location elements carried by PIDF-LO (see [RFC4119] (Peterson, J., “A Presence-based GEOPRIV Location Object Format,” December 2005.)). The security considerations of RFC 4119 [RFC4119] (Peterson, J., “A Presence-based GEOPRIV Location Object Format,” December 2005.) are applicable to this document.

7.  IANA Considerations

This document does not require actions by IANA.

8.  Acknowledgements

We would like to thank Klaus Darilion, Cullen Jennings, Rohan Mahy, Carl Reed, Brian Rosen, and Martin Thomson for their comments.

9.  References

9.1. Normative References

9.2. Informative References

Appendix A.  Transferring Multiple Location Objects within SIP

To show the path of an object, it may be useful to deliver multiple location vector objects in one PIDF-LO document to reduce the number of notifications. The <timed-presence> element [RFC4481] (Schulzrinne, H., “Timed Presence Extensions to the Presence Information Data Format (PIDF) to Indicate Status Information for Past and Future Time Intervals,” July 2006.) can contain multiple location objects, with the structure shown in Figure 2 (Structure of Handling Multiple Location Objects) and an example in Figure 3 (Example showing multiple Location Vectors transmitted simultaneously.).

   <?xml version="1.0" encoding="UTF-8"?>
   <presence>

         <device>

               <gp:geopriv>
                ..........
               </gp:geopriv>

               <timestamp>.....</timestamp>

               <timed-status from="start-time" until="end-time">
                    <gp:geopriv>
                    ............
                    </gp:geopriv>

                    <gp:geopriv>
                    ...........
                    </gp:geopriv>

               </timed-status>
         </device>

         <tuple>
         .......
         </tuple>

         <person>
         .......
         </person>
   </presence>

The following example shows multiple PIDF-LO using <timed-status>.

<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
  xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
  xmlns:gml="urn:opengis:specification:gml:schema-xsd:feature:v3.0"
  entity="pres:geotarget@example.com">
  <device id="sg89ae">
         <gp:geopriv>
           <gp:location-info>
               <gml:location>
                  <gml:Point>
                     <gml:pos>140. -35.</gml:pos>
                  </gml:Point>
               </gml:location>
           <gml:speed uom="#m/s">12</gml:speed>
           </gp:location-info>
           <gp:usage-rules>
             <gp:retransmission-allowed>no</gp:retransmission-allowed>
             <gp:retention-expiry>2003-06-23T04:57:29Z
             </gp:retention-expiry>
           </gp:usage-rules>
         </gp:geopriv>
       <timestamp>2003-06-22T20:57:29Z</timestamp>

       <timed-statusfrom="2005-08-15T10:20:00.000-05:00"
          until="2005-08-22T19:30:00.000-05:00">>
          <gp:geopriv>
            <gp:location-info>
               <gml:location>
                  <gml:Point>
                     <gml:pos>110. -35.</gml:pos>
                  </gml:Point>
               </gml:location>
               <gml:speed uom="#m/s">10</gml:speed>
           </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>yes</gp:retransmission-allowed>
              <gp:retention-expiry>2003-06-23T04:55:29Z
              </gp:retention-expiry>
            </gp:usage-rules>
          </gp:geopriv>
          <gp:geopriv>
            <gp:location-info>
               <gml:location>
                  <gml:Point>
                     <gml:pos>114. -35.</gml:pos>
                  </gml:Point>
               </gml:location>
               <gml:speed uom="#m/s">18</gml:speed>
            </gp:location-info>
           <gp:usage-rules>
             <gp:retransmission-allowed>yes</gp:retransmission-allowed>
             <gp:retention-expiry>2003-06-23T04:53:29Z
             </gp:retention-expiry>
           </gp:usage-rules>
         </gp:geopriv>
       </timed-status>

     </device>
</presence>

Authors' Addresses

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