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Versions: (draft-winterbottom-geopriv-pdif-lo-profile) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 5491

Geopriv                                                  J. Winterbottom
Internet-Draft                                                M. Thomson
Expires: September 4, 2006                            Andrew Corporation
                                                           H. Tschofenig
                                                                 Siemens
                                                           March 3, 2006


GEOPRIV PIDF-LO Usage Clarification, Considerations and Recommendations
               draft-ietf-geopriv-pdif-lo-profile-03.txt

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The Presence Information Data Format Location Object (PIDF-LO)
   specification provides a flexible and versatile means to represent
   location information.  There are, however, circumstances that arise
   when information needs to be constrained in how it is represented so
   that the number of options that need to be implemented in order to
   make use of it are reduced.  There is growing interest in being able



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   to use location information contained in a PIDF-LO for routing
   applications.  To allow successfully interoperability between
   applications, location information needs to be normative and more
   tightly constrained than is currently specified in the PIDF-LO.  This
   document makes recommendations on how to constrain, represent and
   interpret locations in a PIDF-LO.  It further recommends a subset of
   GML that MUST be implemented by applications involved in location
   based routing.


Table of Contents

   1.  CHANGES SINCE LAST TIME  . . . . . . . . . . . . . . . . . . .  3
     1.1.  03 changes . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  01 changes . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Using Location Information . . . . . . . . . . . . . . . . . .  6
     4.1.  Single Civic Location Information  . . . . . . . . . . . .  7
     4.2.  Civic and Geospatial Location Information  . . . . . . . .  8
     4.3.  Manual/Automatic Configuration of Location Information . . 11
   5.  Geodetic Coordinate Representation . . . . . . . . . . . . . . 12
   6.  Geodetic Shape Representation  . . . . . . . . . . . . . . . . 13
   7.  Recommendations  . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 17
   11. Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 18
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     12.1. Normative references . . . . . . . . . . . . . . . . . . . 19
     12.2. Informative References . . . . . . . . . . . . . . . . . . 19
   Appendix A.  Creating a PIDF-LO from DHCP Geo Encoded Data . . . . 20
     A.1.  Latitude and Longitude . . . . . . . . . . . . . . . . . . 20
     A.2.  Altitude . . . . . . . . . . . . . . . . . . . . . . . . . 22
     A.3.  Generating the PIDF-LO . . . . . . . . . . . . . . . . . . 22
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27
   Intellectual Property and Copyright Statements . . . . . . . . . . 28














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1.  CHANGES SINCE LAST TIME

   [[This section is informational only and will be removed before the
   final version.]]

1.1.  03 changes

   Removed some shape defintions, ellipses, arcbands.

   Removed OMA shape definition comparisons.

   Modified examples to use new civicAddr draft data.

   Made extensive references to the GeoShape Draft.

1.2.  01 changes

   minor changes to the abstract.

   Minor changes to the introduction.

   Added and appendix to take implementers through how to create a
   PIDF-LO from data received using DHCP option 123 as defined in [2].

   Rectified examples to use position and pos rather than location and
   point.

   Corrected example 3 so that it does not violate SIP rules.

   Added addition geopriv elements to the status component of the figure
   in "Using Location Information" to more accurately reflect the
   cardinality issues.

   Revised text in section Geodetic Coordinate Representation.  Removed
   last example as this was addressed with the change to position and
   pos in previous examples.















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2.  Introduction

   The Presence Information Data Format Location Object (PIDF-LO) [3] is
   the IETF recommended way of encoding location information and
   associated privacy policies.  Location information in a PIDF-LO may
   be described in a geospatial manner based on a subset of GMLv3, or as
   civic location information [4].  A GML profile for expressing
   geodetic shapes in a PIDF-LO is described in [5].Uses for PIDF-LO are
   envisioned in the context of numerous location based applications.
   This document makes recommendations for formats and conventions to
   make interoperability less problematic.








































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3.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [1].

   In this document a "discrete location" is defined as a location that
   can be found based on the information used to describe it.  It is not
   necessarily a single point in space, but may be an area or volume
   depending on what is being defined and the required precision.









































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4.  Using Location Information

   The PIDF format provides for an unbounded number of tuples.  The
   geopriv element resides inside the status component of a tuple, hence
   a single PIDF document may contain an arbitrary number of location
   objects some or all of which may be contradictory or complementary.
   The actual location information is contained inside a <location-info>
   element, and there may be one or more actual locations described
   inside the <location-info> element.

   Graphically, the structure of the PIDF/PIDF-LO can be depicted as
   follows:


   PIDF document
      tuple 1
          status
               geopriv
                   location-info
                       civicAddress
                        location
                    usage-rules
               geopriv 2
               geopriv 3
               .
               .
               .

      tuple 2
      tuple 3



   All of these potential sources and storage places for location lead
   to confusion for the generators, conveyors and users of location
   information.  Practical experience within the United States National
   Emergency Number Association (NENA) in trying to solve these
   ambiguities led the following conventions being adopted:

   Rule #1: A geopriv element MUST describe a discrete location.


   Rule #2: Where a discrete location can be uniquely described in more
      than one way, each location description SHOULD reside in a
      separate tuple.






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   Rule #3: Providing more than one location in a single presence
      document (PIDF) MUST only be done if all objects describe the same
      location.


   Rule #4: Providing more than one location in a single <location-info>
      element SHOULD be avoided where possible.


   Rule #5: When providing more than one location in a single
      <location-info> element the locations MUST be provided by a common
      source.


   Rule #6: Providing more than one location in a single <location-info>
      element SHOULD only be done if they form a complex to describe the
      same location.  For example, a geodetic location describing a
      point, and a civic location indicating the floor in a building.


   Rule #7: Where a location complex is provided in a single
      <location-info> element, the macro locations MUST be provided
      first.  For example, a geodetic location describing an area, and a
      civic location indicating the floor MUST be represented with the
      area first followed by the civic location.


   Rule #8: Where a PIDF document contains more than one tuple
      containing a status element with a geopriv location element , the
      priority of tuples SHOULD be based on tuple position within the
      PIDF document.  That is to say, the tuple with the highest
      priority location occurs earliest in the PIDF document.  Initial
      priority SHOULD be determined by the originating UA, the final
      priority MAY be determined by a proxy along the way, or the UAS.


   Rule #9: Where multiple PIDF documents are contained within a single
      request, document selection SHOULD be based on document order.

   The following examples illustrate the application of these rules.

4.1.  Single Civic Location Information

   Jane is at a coffee shop on the ground floor of a large shopping
   mall.  Jane turns on her laptop and connects to the coffee-shop's
   WiFi hotspot, Jane obtains a complete civic address for her current
   location, for example using [6].  A Location Object is constructed
   consisting of a single PIDF document, with a single geopriv tuple,



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   and a single location residing in the <location-info> element.  This
   document is unambiguous, and should be interpreted correctly if sent
   of the network.

4.2.  Civic and Geospatial Location Information

   Mike is visiting his Seattle office and connects his laptop into the
   Ethernet port in a spare cube.  Mike's computer receives a location
   over DHCP as defined in [2].  In this case the location is a geodetic
   location, with the altitude represented as a building floor number.
   This is constructed by Mike's computer into the following PIDF
   document:







































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   <?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:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
      xmlns:gs="urn:ietf:params:xml:ns:pidf:geopriv10:geoShape"
      entity="pres:mike@seattle.example.com">
     <tuple id="sg89ab">
       <status>
         <gp:geopriv>
           <gp:location-info>
             <cl:civicAddress>
                <cl:FLR>2</cl:FLR>
             </cl:civicAddress>
           </gp:location-info>
           <gp:usage-rules/>
         </gp:geopriv>
       </status>
       <timestamp>2006-01-30T20:57:29Z</timestamp>
     </tuple>
     <tuple id="sg89ae">
       <status>
         <gp:geopriv>
           <gp:location-info>
             <Polygon srsName="urn:ogc:def::crs:EPSG::4326"
                      xmlns="http://www.opengis.net/gml">
               <exterior>
                 <LinearRing>
                   <pos>37.775 -122.4194</pos>
                   <pos>37.555 -122.4194</pos>
                   <pos>37.555 -122.4264</pos>
                   <pos>37.775 -122.4264</pos>
                   <pos>37.775 -122.4194</pos>
                 </LinearRing>
               </exterior>
             </Polygon>
           </gp:location-info>
           <gp:usage-rules/>
         </gp:geopriv>
       </status>
       <timestamp>2006-01-30T20:57:29Z</timestamp>
     </tuple>
   </presence>


   The constructed PIDF document contains two geopriv elements each in a
   separate PIDF tuple, the first being a civic address made up of only
   floor, the second containing the provided geodetic information.  If
   the location is required for routing purposes, which information is



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   used?  Applying rule #8, we will likely fail, or at a minimum need to
   fall back to the second tuple describing the geodetic location, a
   route described by floor only is not precise enough in the normal
   case to permit route selection.  If rule #6 and #7 are applied, then
   the revised PIDF-LO document creates a complex as shown below.


   <?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:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
      xmlns:gs="urn:ietf:params:xml:ns:pidf:geopriv10:geoShape"
      entity="pres:mike@seattle.example.com">
     <tuple id="sg89ab">
       <status>
         <gp:geopriv>
           <gp:location-info>
             <Polygon srsName="urn:ogc:def:crs:EPSG::4326"
                      xmlns="http://www.opengis.net/gml">
               <exterior>
                 <LinearRing>
                   <pos>37.775 -122.4194</pos>
                   <pos>37.555 -122.4194</pos>
                   <pos>37.555 -122.4264</pos>
                   <pos>37.775 -122.4264</pos>
                   <pos>37.775 -122.4194</pos>
                 </LinearRing>
               </exterior>
             </Polygon>
             <cl:civicAddress>
               <cl:FLR>2</cl:FLR>
             </cl:civicAddress>
           </gp:location-info>
           <gp:usage-rules/>
         </gp:geopriv>
       </status>
       <timestamp>2003-06-22T20:57:29Z</timestamp>
     </tuple>
   </presence>


   It is now clear that the main location of user is inside the
   rectangle bounded by the geodetic coordinates specfied.  Further that
   the user is on the second floor of the building located at these
   coordinates.






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4.3.  Manual/Automatic Configuration of Location Information

   Loraine has a predefined civic location stored in her laptop, since
   she normally lives in Sydney, the address in her address is for her
   Sydney-based apartment.  Loraine decides to visit sunny San
   Francisco, and when she gets there she plugs in her laptop and makes
   a call.  Loraine's laptop receives a new location from the visited
   network in San Francisco.  As ths system cannot be sure that the pre-
   existing and new location describe the same place, Loraine's computer
   generates a new PIDF-LO and will use this to represent Loraine's
   location.  If Loraine's computer were to add the new location to her
   existing PIDF location document (breaking rule #3), then the correct
   information may still be interpretted by location recipient providing
   Loraine's system applies rule #9.  In this case the resulting order
   of location information in the PIDF document should be San Francisco
   first, followed by Sydney.  Since the information is provided by
   different sources, rule #8 should also be applied and the information
   placed in different tuples with San Francisco first.

































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5.  Geodetic Coordinate Representation

   The geodetic examples provided in [3] are illustrated using the gml:
   location element which uses the gml:coordinates elements (inside the
   gml:Point element) and this representation has several drawbacks.
   Firstly, it has been deprecated in later versions of GML (3.1 and
   beyond) making it inadvisable to use for new applications.  Secondly,
   the format of the coordinates type is opaque and so can be difficult
   to parse and interpret to ensure consistent results, as the same
   geodetic location can be expressed in a variety of ways.  The PIDF-LO
   Geodetic Shapes specification [5] provides a specific GML profile for
   expressing commonly used shapes using simple GML representations.
   The shapes defined in [5] are the recommended shapes to ensure
   interoperability between location based applications.





































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6.  Geodetic Shape Representation

   The cellular mobile world today makes extensive use of geodetic based
   location information for emergency and other location-based
   applications.  Generally these locations are expressed as a point
   (either in two or three dimensions) and an area or volume of
   uncertainty around the point.  In theory, the area or volume
   represents a coverage in which the user has a relatively high
   probability of being found, and the point is a convenient means of
   defining the centroid for the area or volume.  In practice, most
   systems use the point as an absolute value and ignore the
   uncertainty.  It is difficult to determine if systems have been
   implement in this manner for simplicity, and even more difficult to
   predict if uncertainty will play a more important role in the future.
   An important decision is whether an uncertainty area should be
   specified.

   [5] defines eight shape types most of which are easily translated in
   shapes definitions used in other applications and protocol, such as
   Open Mobile Alliance (OMA) Mobile Location Protocol (MLP).  For
   completeness the shape defined in [5] are listed below:

   o  Point (2d or 3d)

   o  Polygon (2d)

   o  Circle (2d)

   o  Ellipse (2d)

   o  Arc band (2d)

   o  Sphere (3d circle)

   o  Ellipsoid (3d)

   o  Prism (3d polygon)

   [5] also describes a standard set of coordinate reference systems
   (CRS), unit of measure and conventions relating to lines and
   distances that will be repeated here.










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7.  Recommendations

   As a summary this document gives a few recommendations on the usage
   of location information in PIDF-LO.  Nine rules specified in
   Section 4 give guidelines on the ambiguity of PIDF-LO with regard to
   the occurrence of multiple location information.  It is recommend
   that only the shape types and shape representations described in [5]
   be used to express geodetic locations for exchange between general
   applications.  By standardizing geodetic data representation
   interoperability issues are mitigated.

   If Geodetic information is to be provided via DHCP, then a minimum
   resolution of 20 bits SHOULD be specified for both the Latitude and
   Longitude fields to achieve sub 100 metre precision.  Where only two
   dimensional objects are required polygons SHOULD be used to express
   the enclosed area.  Where 3 dimensions are required a rectangular
   prism SHOULD be used.


































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8.  Security Considerations

   The primary security considerations relate to how location
   information is conveyed and used, which are outside the scope of this
   document.  This document is intended to serve only as a set of
   guidelines as to which elements MUST or SHOULD be implemented by
   systems wishing to perform location dependent routing.  The
   ramification of such recommendations is that they extend to devices
   and clients that wish to make use of such services.










































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9.  IANA Considerations

   This document does not introduce any IANA considerations.
















































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10.  Acknowledgments

   The authors would like to thank the GEOPRIV working group for their
   discussions in the context of PIDF-LO, in particular Carl Reed, Ron
   Lake, James Polk and Henning Schulzrinne.  Furthermore, we would like
   to thank Jon Peterson as the author of PIDF-LO and Nadine Abbott for
   her constructive comments in clarifying some aspects of the document.












































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11.  Open Issues

   Do we need to indicate which shapes are acceptable for emergency
   calling?  Ceratinly not all can be used today, for example the
   polygon and prism types will not work with NENA i2 as it is defined
   today due to restrictions over the VE2 interface [7].













































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12.  References

12.1.  Normative references

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", March 1997.

12.2.  Informative References

   [2]   Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
         Configuration Protocol Option for Coordinate-based Location
         Configuration Information", RFC 3825, July 2004.

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

   [4]   Thomson, M. and J. Winterbottom, "Revised Civic Location Format
         for PIDF-LO", draft-ietf-geopriv-revised-civic-lo-01 (work in
         progress), January 2006.

   [5]   Thomson, M., "draft-thomson-geopriv-geo-shape, Geodetic Shapes
         for the Representation of Uncertainty in PIDF-LO",
         January 2006.

   [6]   Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
         and DHCPv6) Option for Civic  Addresses Configuration
         Information", draft-ietf-geopriv-dhcp-civil-09 (work in
         progress), January 2006.

   [7]   "NENA Standard for the Implementation of the Wireless Emergency
         Service Protocol E2 Interface".

   [8]   Schulzrinne, H., "A Document Format for Expressing Privacy
         Preferences", draft-ietf-geopriv-common-policy-07 (work in
         progress), February 2006.

   [9]   "3GPP TS 23.032 V6.0.0 3rd Generation Partnership Project;
         Technical Specification Group Code Network; Universal
         Geographic Area Description (GAD)".

   [10]  "TR-45 J-STD-036-AD-2 Enhanced Wireless 9-1-1 Phase 2".










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Appendix A.  Creating a PIDF-LO from DHCP Geo Encoded Data

   RFC-3825 [2] describes a means by which an end-point may learns it
   location from information encoded into DHCP option 123.  The
   following section describes how and end-point can take this
   information and represent it in a well formed PIDF-LO describing this
   geodetic location.

   The location information described in RFC-3825 consists of a
   latitude, longitude, altitude and datum.

A.1.  Latitude and Longitude

   The latitude and longitude values are represented in degrees and
   decimal degrees.  Latitude values are positive if north of the
   equator, and negative if south of the equator.  Similarly
   longitudinal values are positive if east of the Greenwich meridian,
   and negative if west of the Greenwich meridian.

   The latitude and longitude values are each 34 bit long fields
   consisting of a 9 bit integer component and a 25 bit fraction
   component, with negative numbers being represented in 2s complement
   notation.  The latitude and longitude fields are each proceeded by a
   6 bit resolution field, the LaRes for latitude, and the LoRes for
   longitude.  The value in the LaRes field indicates the number of
   significant bits to interpret in the Latitude field, while the value
   in the LoRes field indicates the number of significant bits to
   interpret in the Longitude field.

   For example, if you are in Wollongong Australia which is located at
   34 Degrees 25 minutes South and 150 degrees 32 minutes East this
   would translate to -34.41667, 150.53333 in decimal degrees.  If these
   numbers are translated to their full 34 bit representations, then we
   arrive the following:

   Latitude = 111011101.1001010101010101000111010

   Longitude = 0100101101000100010001000010100001

   RFC-3825, uses the LaRes and LoRes values to specify a lower and
   upper boundary for location thereby specifying an area.  The size of
   the area specified is directly related to the value specified in the
   LaRes and LoRes fields.

   Using the previous example, if LaRes is set 7, then lower latitude
   boundary can be calculated as -256+128+64+16+8+4, which is -36
   degrees, the upper boundary then becomes -256+128+64+16+8+4+2+1 which
   is -35 degrees.  LoRes may be used similarly for Longitude.



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   So what level of precision is useful?  Well, certain types of
   applications and regulations call for different levels of precision,
   and the required precision may vary depending on how the location was
   determined.  For Cellular 911 calls in the United States, for
   example, if the network measures the location then the caller should
   be within 100 metres, while if the handset does the measurement then
   the location should be within 50 metres.  Since DHCP is a network
   based mechanism we will benchmark off 100 metres (approximately 330
   ft) which is still a large area.

   For simplicity we shall assume that we are defining a square, in
   which we are equally to appear anywhere.  The greatest distance
   through this square is across the diagonal, so we make this 100
   metres.


   +----------------------+
   |                    _/|
   |                  _/  |
   |                _/    |
   |              _/      |
   |            _/        |
   |       100_/ metres   |
   |        _/            |
   |      _/              |
   |    _/                |
   |  _/                  |
   |_/                    |
   +----------------------+


   The distance between the top and the bottom and the left and the
   right is the same, the area being a square, and this works out to be
   70.7 metres.  When expressed in decimal degrees, the third point
   after the decimal place represents about 100 metre precision, this
   equates to 10 binary places of fractional part.  A 70 metre distance
   is required, so 11 fractional binary digits are necessary resulting
   in a total of 20 bits of precision.

   With -34.4167, 150.5333 encoded with 20 bits of precision for the
   LaRes and LoRes, the corners of the enclosing square are:


   Point 1 (-34.4170, 150.5332)
   Point 2 (-34.4170, 150.5337)
   Point 3 (-34.4165, 150.5332)
   Point 4 (-34.4165, 150.5337)




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A.2.  Altitude

   The altitude elements define how the altitude is encoded and to what
   level of precision.  The units for altitude are either metres, or
   floors, with the actual measurement being encoded in a similar manner
   to those for latitude and longitude, but with 22 bit integer, and 8
   bit fractional components.

A.3.  Generating the PIDF-LO

   If altitude is not required, or is expressed in floors then a
   geodetic location expressed by a polygon SHOULD be used, with points
   expressed in a counter-clockwise direction.  If the altitude is
   expressed in floors and is required, the altitude SHOULD be expressed
   as a civic floor number as part of the same location-info element.
   In the example above the GML for the location would be expressed as
   follows:


     <Polygon srsName="urn:ogc:def:crs:EPSG::4326"
              xmlns="http://www.opengis.net/gml">
       <exterior>
         <LinearRing>
            <pos>-34.4165 150.5332</pos>
            <pos>-34.4170 150.5532</pos>
            <pos>-34.4170 150.5537</pos>
            <pos>-34.4165 150.5337</pos>
            <pos>-34.4165 150.5332</pos>
         </LinearRing>
        </exterior>
      </Polygon>


   If a floor number of say 3 were included, then the location-info
   element would contain the above information and the following:


   <civicAddress
      xlmns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
      <FLR>2</FLR>
   </civicAddress>


   When altitude is expressed as an integer and fractional component, as
   with the latitude and longitude, it expresses a range which requires
   the prism form to be used.  Care must be taken to ensure that the
   points are defined in a counter-clowise direction to ensure that the
   upward normal points up.



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   Extending the previous example to include an altitude expressed in
   metres rather than floors.  AltRes is set to a value of 19, and the
   Altitude value is set to 34.  Using similar techniques as shown in
   the latitude and longitude section, a range of altitudes between 32
   metres and 40 metres is described.  The prism would therefore be
   defined as follows:



   <Prism  srsName="urn:ogc:def:crs:EPSG::4976"
           xmlns:gs="urn:ietf:params:xml:ns:pidf:geopriv10:geoShape"
           xmlns:gml="http://www.opengis.net/gml">
      <base>
         <gml:Polygon>
            <gml:exterior>
               <gml:LinearRing>
                  <gml:pos>-34.4165 150.5332 32</gml:pos>
                  <gml:pos>-34.4170 150.5532 32</gml:pos>
                  <gml:pos>-34.4170 150.5537 32</gml:pos>
                  <gml:pos>-34.4165 150.5337 32</gml:pos>
                  <gml:pos>-34.4165 150.5332 32</gml:pos>
               </gml:LinearRing>
            </gml:exterior>
         </gml:Polygon>
      </base>
      <height uom="urn:ogc:def:uom:EPSG::9001">
         8
      </height>
   </Prism>


   The Method value SHOULD be set to DHCP.  Note that this case, the
   DHCP is referring to the way in which location information was
   delivered to the IP-device, and not necessarily how the location was
   determined.

   The timestamp value SHOULD be set to the time that location was
   retrieved from the DHCP server.

   The client application MAY insert any usage rules that are pertinent
   to the user of the device and that comply with [8].  A guideline is
   that the any retention-expiry value SHOULD NOT exceed the current
   lease time.

   The Provided-By element SHOULD NOT be populated as this is not
   provided by the source of the location information.

   The 3 completed PIDF-LO representations are provided below, and



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   represent a location without altitude, a location with a civic
   altitude, and a location represented as a 3 dimensional rectangular
   prism.


   <?xml version="1.0"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
             xmlns:pidf="urn:ietf:params:xml:ns:pidf"
             xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
             xmlns:gs="urn:ietf:params:xml:ns:pidf:geopriv10:geoShape"
             xmlns:gml="http://www.opengis.net/gml"
             entity="pres:user@example.com">
     <tuple id="a6fea09">
       <status>
         <gp:geopriv>
           <gp:location-info>
               <gml:Polygon srsName="urn:ogc:def:crs:EPSG::4326">
                  <gml:exterior>
                     <gml:LinearRing>
                        <gml:pos>-34.4165 150.5332</gml:pos>
                        <gml:pos>-34.4170 150.5532</gml:pos>
                        <gml:pos>-34.4170 150.5537</gml:pos>
                        <gml:pos>-34.4165 150.5337</gml:pos>
                        <gml:pos>-34.4165 150.5332</gml:pos>
                     </gml:LinearRing>
                  </gml:exterior>
               </gml:Polygon>
           </gp:location-info>
           <gp:usage-rules/>
                <gp:method>DHCP</gp:method>
         </gp:geopriv>
       </status>
       <timestamp>2005-07-05T14:49:53+10:00</timestamp>
     </tuple>
   </presence>
















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   <?xml version="1.0"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
             xmlns:pidf="urn:ietf:params:xml:ns:pidf"
             xmlns:cl=" urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
             xmlns:gs="urn:ietf:params:xml:ns:pidf:geopriv10:geoShape"
             xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
             xmlns:gml="http://www.opengis.net/gml"
             entity="pres:user@example.com">
     <tuple id="a6fea09">
       <status>
         <gp:geopriv>
           <gp:location-info>
              <gml:Polygon srsName="urn:ogc:def:crs:EPSG::4326">
                  <gml:exterior>
                     <gml:LinearRing>
                        <gml:pos>-34.4165 150.5332</gml:pos>
                        <gml:pos>-34.4170 150.5532</gml:pos>
                        <gml:pos>-34.4170 150.5537</gml:pos>
                        <gml:pos>-34.4165 150.5337</gml:pos>
                        <gml:pos>-34.4165 150.5332</gml:pos>
                     </gml:LinearRing>
                  </gml:exterior>
               </gml:Polygon>
             <cl:civilAddress>
               <cl:FLR>2</cl:FLR>
             </cl:civilAddress>
           </gp:location-info>
           <gp:usage-rules/>
                <gp:method>DHCP</gp:method>
         </gp:geopriv>
       </status>
       <timestamp>2005-07-05T14:49:53+10:00</timestamp>
     </tuple>
   </presence>

















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   <?xml version="1.0"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
             xmlns:pidf="urn:ietf:params:xml:ns:pidf"
             xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
             xmlns:gs="urn:ietf:params:xml:ns:pidf:geopriv10:geoShape"
             xmlns:gml="http://www.opengis.net/gml"
             entity="pres:user@example.com">
     <tuple id="a6fea09">
       <status>
         <gp:geopriv>
           <gp:location-info>
               <gs:Prism  srsName="urn:ogc:def:crs:EPSG::4976">
                  <gs:base>
                     <gml:Polygon>
                        <gml:exterior>
                           <gml:LinearRing>
                              <gml:pos>-34.4165 150.5332 32</gml:pos>
                              <gml:pos>-34.4170 150.5532 32</gml:pos>
                              <gml:pos>-34.4170 150.5537 32</gml:pos>
                              <gml:pos>-34.4165 150.5337 32</gml:pos>
                              <gml:pos>-34.4165 150.5332 32</gml:pos>
                           </gml:LinearRing>
                        </gml:exterior>
                     </gml:Polygon>
                  </gs:base>
                  <gs:height uom="urn:ogc:def:uom:EPSG::9001">
                     8
                  </gs:height>
               </gs:Prism>
           </gp:location-info>
           <gp:usage-rules/>
           <gp:method>DHCP</gp:method>
         </gp:geopriv>
       </status>
       <timestamp>2005-07-05T14:49:53+10:00</timestamp>
     </tuple>
   </presence>














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Authors' Addresses

   James Winterbottom
   Andrew Corporation
   Wollongong
   NSW Australia

   Email: james.winterbottom@andrew.com


   Martin Thomson
   Andrew Corporation
   Wollongong
   NSW Australia

   Email: martin.thomson@andrew.com


   Hannes Tschofenig
   Siemens
   Otto-Hahn-Ring 6
   Munich, Bavaria  81739
   Germany

   Email: Hannes.Tschofenig@siemens.com


























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