


Network Working Group                                           A. Forte
Internet-Draft                                                      AT&T
Intended status: Experimental                             H. Schulzrinne
Expires: March 10, 2012                              Columbia University
                                                       September 7, 2011


       Location-to-Service Translation (LoST) Protocol Extensions
                   draft-forte-lost-extensions-08.txt

Abstract

   An important class of location-based services answer the question
   "What instances of this service are closest to me?"  Examples include
   finding restaurants, gas stations, stores, automated teller machines,
   wireless access points (hot spots) or parking spaces.  Currently, the
   Location-to-Service Translation (LoST) protocol only supports mapping
   locations to a single service based on service regions.  This
   document describes an extension that allows queries of the type "N
   nearest", "within distance X" and "served by".

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 10, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements Notation  . . . . . . . . . . . . . . . . . . . .  3
   3.  Service Regions  . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  New <findService> Query Types: "N nearest", "within
       distance X" and "served by"  . . . . . . . . . . . . . . . . .  5
   5.  LoST Extensions  . . . . . . . . . . . . . . . . . . . . . . .  5
     5.1.  New Use of Shapes in Queries . . . . . . . . . . . . . . .  5
     5.2.  Queries Based on Service Regions . . . . . . . . . . . . .  8
     5.3.  Difference Between "within distance X" and "served by"
           Queries  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.4.  Limiting the Number of Returned Service URIs . . . . . . . 11
     5.5.  The <serviceLocation> Element in Responses . . . . . . . . 13
   6.  Emergency Services . . . . . . . . . . . . . . . . . . . . . . 16
   7.  Relax NG Schema  . . . . . . . . . . . . . . . . . . . . . . . 17
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
     9.1.  LoST Extensions Relax NG Schema Registration . . . . . . . 19
     9.2.  LoST Extensions Namespace Registration . . . . . . . . . . 20
   10. Non-Normative RELAX NG Schema in XML Syntax  . . . . . . . . . 20
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 23
   12. Normative References . . . . . . . . . . . . . . . . . . . . . 23
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24





















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1.  Introduction

   The Location-to-Service Translation (LoST) protocol [RFC5222] maps
   service identifiers (URNs) and civic or geospatial information to
   service URIs, based on service regions.  While motivated by mapping
   locations to the public safety answering point (PSAP) serving that
   location, the protocol has been designed to generalize to other
   location mapping services.

   However, the current LoST query model assumes that each service URI
   has a service region and that service regions do not overlap.  This
   fits the emergency services model, where the service region of a PSAP
   is given by jurisdictional boundaries, but does not work as well for
   other services that do not have clearly defined boundaries.  For
   example, any given location is likely served by a number of different
   restaurants, depending on how far the prospective customer is willing
   to travel.

   We extend LoST with three additional <findService> query types,
   giving the protocol the ability to find the N nearest instances of a
   particular service, all services within a given distance and all
   services whose service region includes the client's current location.


2.  Requirements Notation

   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 [RFC2119].


3.  Service Regions

   Generally speaking, service regions apply only to a subset of
   services.

   In Section 1 of [RFC5222] a service region is defined as follows:

   "To minimize round trips and to provide robustness against network
   failures, LoST supports caching of individual mappings and indicates
   the region for which the same answer would be returned ("service
   region")."

   and in Section 5.5 of [RFC5222]:

   "A response MAY indicate the region for which the service URL
   returned would be the same as in the actual query, the so-called
   service region."



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   For emergency services, service region and service area, as defined
   in [RFC5222], represent the same geographical area.  This is due to
   the fact that each PSAP serves its own area without overlapping with
   the service area of any other PSAP.  For as long as the client is
   located in the service area of a PSAP, the same PSAP is returned by
   the LoST server that is, the service region does not change.  A
   service region is the service area of a PSAP.

   For non-emergency services different points of service may have
   different overlapping service areas.  This means that one service
   region will probably include a large number of service areas.  Since
   for each query we can get a large number of service URIs, a service
   region as per definition above would be the region within which a
   user would get the same set of service URIs.  If one or more of the
   URIs in the set changes, the set of URIs changes that is, the service
   region changes.  Therefore, for non-emergency services a service
   region as defined in [RFC5222] would change very frequently, making
   the use of service regions as described in [RFC5222] not that useful.

   Generally speaking, we can divide location-based services into two
   main categories.

   Services based on:

   o  how far they are from the user (e.g., ATM machines, takeout)

   o  whether or not their service area includes the client's current
      location (e.g., pizza delivery, NG9-1-1)

   For services included in the first category service areas and
   therefore service regions are not relevant while they are important
   for services included in the second category.  This distinction
   becomes obvious if we consider the difference between takeout (first
   category) and delivery (second category), for example.  In the case
   of takeout, the user wants to go to a particular restaurant and buy
   dinner regardless of his location falling in the restaurant service
   area or not.  For delivery, the user cares about the restaurant
   service area as the restaurant will deliver food to him only if the
   user's location falls within the restaurant service area.

   There is a clear distinction between services that require service
   areas and services that do not.  The LoST extensions defined in this
   document take this into account by using the service classification
   mentioned above.







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4.  New <findService> Query Types: "N nearest", "within distance X" and
    "served by"

   We introduce three new types of <findService> queries that is, "N
   nearest", "within distance X" and "served by".  The first query
   returns the N points of interest closest to the client's physical
   location, the second query discovers all those points of interest
   located within a given distance from the client's physical location,
   the third query returns all those points of interest whose service
   area includes the client's current location.


5.  LoST Extensions

   For queries "within distance X", the LoST client needs to specify to
   the server the range within which instances of a particular service
   should be searched.  In order to do this, we make use of various
   shapes [RFC5491] in LoST queries.

   For queries "served by", the LoST client needs to let the server know
   that it MUST return only those services whose service area includes
   the client's current location.  In order to do this we introduce the
   <region> element in <findService> queries.  Service region boundaries
   MAY be returned in a LoST <findServiceResponse> as described in
   [RFC5222].

   For queries "N nearest", the LoST client needs to let the server know
   N, that is, the maximum number of service URIs to be returned in a
   response.  In order to specify this, we introduce the <limit> element
   in <findService> queries.

   Also, we introduce a new element in LoST responses, namely
   <serviceLocation>.  This new element is used by the server to
   indicate to the client the physical location of points of interest.
   In doing so, the client can compute the distance and other metrics
   between its current location and the points of interest.

   The new elements <region>, <limit> and <serviceLocation> are defined
   in the "lost-ext" namespace.  This new namespace is defined in
   Section 6.

5.1.  New Use of Shapes in Queries

   In [RFC5491] different shapes are defined in order to represent a
   point and an area of uncertainty within which the user might be
   situated.  While this remains true for "served by" queries, for
   "within distance X" queries such shapes can be interpreted as the
   area within which we want to find a service.  In particular, I want



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   to search for points of service within that area because my location
   is within that area with a certain probability.  We can think of the
   area of uncertainty in a shape as the probability that a user might
   be within that area and so we want to look for services within that
   area.  All we are doing with a "within distance X" query is to
   manually set the uncertainty level in user location to a value of X.

   For example, Figure 1 shows a "within distance X" <findService>
   geodetic query using the circular shape.  With the query shown in
   Figure 1, we are asking the LoST server to send us a list of service
   URIs for pizza places within 200 meters from our approximate position
   specified in <gml:pos>.

   Aside from the circular shape, other shapes are also useful.  In
   particular, there are situations in which it is useful to query for
   services in a certain direction of movement rather than in an exact
   physical location.  For example, if a user is driving North from New
   York City to Boston, it would be useful for this user to be able to
   query for services North of where he currently is that is, not at his
   current physical location nor at his final destination.

   In order to do this, we use shapes such as an ellipse.  The ellipse
   has a major and a minor dimension thus allowing for defining a
   "privileged" direction by having the major dimension in the direction
   of movement.  In the present context the circular shape allows a
   device to search for services in any direction surrounding its
   physical location while shapes such as the ellipse allow the device
   to search for services in a more specific direction.  Figure 2 shows
   a "within distance X" <findService> geodetic query using the
   elliptical shape.  The ellipse shape is defined in Section 5.2.4 of
   [RFC5491].




















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   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:ext="urn:ietf:params:xml:ns:lost-ext"
     xmlns:gml="http://www.opengis.net/gml"
     xmlns:gs="http://www.opengis.net/pidflo/1.0"
     serviceBoundary="value"
     recursive="true">
     <ext:region>false</ext:region>
     <location id="6020688f1ce1896d" profile="geodetic-2d">
       <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326">
         <gml:pos>37.775 -122.422</gml:pos>
         <gs:radius uom="urn:ogc:def:uom:EPSG::9001">
            200
         </gs:radius>
       </gs:Circle>
     </location>
     <service>urn:service:food.pizza</service>
   </findService>


   Figure 1: A 'within distance X' <findService> geodetic query using
   the circular shape (a hypothetical service URN of
   "urn:service:food.pizza" is used)



























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   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:ext="urn:ietf:params:xml:ns:lost-ext"
     xmlns:gml="http://www.opengis.net/gml"
     xmlns:gs="http://www.opengis.net/pidflo/1.0"
     serviceBoundary="value"
     recursive="true">
     <ext:region>false</ext:region>
     <location id="6020688f1ce1896d" profile="geodetic-2d">
       <gs:Ellipse srsName="urn:ogc:def:crs:EPSG::4326">
         <gml:pos>42.5463 -73.2512</gml:pos>
         <gs:semiMajorAxis uom="urn:ogc:def:uom:EPSG::9001">
           1235
         </gs:semiMajorAxis>
         <gs:semiMinorAxis uom="urn:ogc:def:uom:EPSG::9001">
           660
         </gs:semiMinorAxis>
         <gs:orientation uom="urn:ogc:def:uom:EPSG::9102">
           41.2
         </gs:orientation>
       </gs:Ellipse>
     </location>
     <service>urn:service:food.pizza</service>
   </findService>


   Figure 2: A 'within distance X' <findService> geodetic query using
   the elliptical shape (a hypothetical service URN of
   "urn:service:food.pizza" is used)

5.2.  Queries Based on Service Regions

   As mentioned in Section 1, we can divide location-based services into
   two main categories.

   Services based on:

   o  how far they are from the user

   o  whether or not their service area includes the user's current
      location

   A "within distance X" query addresses services included in the first
   category while a "served by" query addresses services included in the
   second category.





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                            __________________________
                            \    *****                \
            ,===============***====,    ***            \
           /              **  \   /         **          \
          /   POI 1     **     \ /            **         \
         /      o      **       X              **         \
        /             **       / \  USER        **         \
       /              **      /   \  0           **         \
      /               **     /     \      POI 3  **          \
     /                 **   /       \       o    **           \
    /          ,--------**-/---------\----------**--,          \
   `=====================**           \________**___|___________\
               |           **                **     |
               |   o         ***          ***       |
               |  POI 2           *****             |
               `------------------------------------'



   Figure 3: LoST client location (circle) overlapping three service
   areas of three different points of interest (POI 1, POI 2, POI 3)

   When querying LoST regarding a specific service, we need to specify
   if such service belongs to either the first or the second category.
   This is necessary since depending on the category the service belongs
   to, the LoST server has to follow a different metric in selecting the
   results to include in the response.

   For example, Figure 3 shows three points of interest with their
   service areas.  The user location that is, the LoST client location,
   is represented by a circular shape (e.g., GPS).  If POI 1, POI 2 and
   POI 3 belong to the first category of service ("within distance X"
   query), their service area is irrelevant, what it matters is how far
   they are from the user.  For such services the shape representing the
   user location represents the distance within which the user wants to
   search for services (see Section 5.1).  In the example shown in
   Figure 3 the LoST server returns only POI 3 as POI 3 is the only
   point of interest falling within the user location represented by the
   circle that is, the area within which the user wants to search for
   services.  On the other hand, if the three points of service belong
   to the second category ("served by" query) then what it matters is
   their service area.  In this second scenario, since the circle
   representing the user location overlaps with all three service areas,
   it means that all three POIs can serve the location of the user and
   the LoST server has to return all three POIs that is, POI 1, POI 2
   and POI 3.

   In order for the client to specify which of the two categories the



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   service belongs to, we introduce the <region> element.  This new
   element is of type boolean.  When its value is false, the LoST server
   MUST perform a search based on the distance between the user and the
   points of service ("within distance X" query).  When its value is
   either true or the <region> element is missing (see Section 5.3), it
   means that the requested service belongs to the second category and a
   search based on service areas MUST be performed by the LoST server
   ("served by" query).  When present, the <region> element MUST be
   conveyed inside the <findService> element defined in [RFC5222].

   For a search based on service regions the LoST server MUST return
   only those services whose service area includes the client's current
   location.  Service region boundaries MAY be returned in a LoST
   <findServiceResponse> as described in [RFC5222].

   <?xml version="1.0" encoding="UTF-8"?>
    <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:ext="urn:ietf:params:xml:ns:lost-ext"
     xmlns:gml="http://www.opengis.net/gml"
     xmlns:gs="http://www.opengis.net/pidflo/1.0"
     serviceBoundary="value" recursive="true">
     <ext:region>true</ext:region>
     <location id="6020688f1ce1896d" profile="geodetic-2d">
       <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326">
         <gml:pos>37.775 -122.422</gml:pos>
         <gs:radius uom="urn:ogc:def:uom:EPSG::9001">
            200
         </gs:radius>
       </gs:Circle>
     </location>
    <service>urn:service:food.pizza</service>
   </findService>

   Figure 4 A 'served by' <findService> geodetic query with the new
   <region> element (a hypothetical service URN of
   "urn:service:food.pizza" is used)

5.3.  Difference Between "within distance X" and "served by" Queries

   Figures 1 and 4 show an example of a "within distance X" query and a
   "served by" query, respectively.  The two types of queries although
   very similar have three important differences.

   o  A "served by" query can support all the shapes a "within distance
      X" query can support plus the point shape.  The point shape does
      not make sense for a "within distance X" query and SHOULD NOT be
      used for such query as it would be equivalent to a within-zero-



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      meters search.

   o  In a "within distance X" query we manually set to X the
      uncertainty level in user location and we search for services
      within such area.  In all other types of queries including a
      "served by" query, the level of uncertainty in user location
      cannot be changed by the user and search based on service areas is
      performed.

   o  In a "within distance X" query the value of the <region> element
      MUST be set to false.  A "served by" query SHALL have the value of
      the <region> element set to true.  If the <region> element is not
      present, its value MUST be assumed to be equal to true and the
      query will be a "served by" query.  This behavior is consistent
      with [RFC5222].

5.4.  Limiting the Number of Returned Service URIs

   Limiting the number of results is helpful, particularly for mobile
   devices with limited bandwidth.  For "N nearest" queries, the client
   needs to be able to tell the server to return no more than N service
   URIs.  In order to specify such limit we introduce a new element,
   namely <limit>.  This new element is OPTIONAL but when present, it
   MUST be conveyed inside the <findService> element defined in
   [RFC5222].

   Figures 5, 6 and 7 show a <findService> geodetic query where the
   client asks the server to return no more than 20 service URIs.  In
   particular, Figure 5 shows a 'N nearest' query, Figure 6 shows a
   query which is a combination of 'N nearest' and 'within distance X'
   while Figure 7 shows a query which is a combination of 'N nearest'
   and 'served by'.  When receiving such queries, the LoST server will
   return a list of no more than 20 points of interest.

   If the available points of interest are more than N, the server has
   to identify, among those, the N points of interest closest to the
   client's physical location and MUST return those in the response.

   When the <limit> element is not present in a <findService> query then
   all available points of interest for the requested type of service
   SHOULD be returned by the LoST server.  This behavior is consistent
   with [RFC5222].









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   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:ext="urn:ietf:params:xml:ns:lost-ext"
     xmlns:gml="http://www.opengis.net/gml"
     serviceBoundary="value" recursive="true">
     <ext:limit>20</ext:limit>
     <location id="6020688f1ce1896d" profile="geodetic-2d">
       <gml:Point id="point1" srsName="urn:ogc:def:crs:EPSG::4326">
         <gml:pos>40.7128 -74.0092</gml:pos>
       </gml:Point>
     </location>
   <service>urn:service:food.pizza</service>
   </findService>

   Figure 5: A 'N nearest' <findService> geodetic query with the new
   <limit> element (a hypothetical service URN of
   "urn:service:food.pizza" is used)


   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:ext="urn:ietf:params:xml:ns:lost-ext"
     xmlns:gml="http://www.opengis.net/gml"
     xmlns:gs="http://www.opengis.net/pidflo/1.0"
     serviceBoundary="value"
     recursive="true">
     <ext:region>false</ext:region>
     <ext:limit>20</ext:limit>
     <location id="6020688f1ce1896d" profile="geodetic-2d">
       <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326">
         <gml:pos>37.775 -122.422</gml:pos>
         <gs:radius uom="urn:ogc:def:uom:EPSG::9001">
            200
         </gs:radius>
       </gs:Circle>
     </location>
     <service>urn:service:food.pizza</service>
   </findService>


   Figure 6: A <findService> geodetic query with the new <limit> and
   <region> elements.  This query is a combination of 'N nearest' and
   'within distance X' queries (a hypothetical service URN of
   "urn:service:food.pizza" is used)





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   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:ext="urn:ietf:params:xml:ns:lost-ext"
     xmlns:gml="http://www.opengis.net/gml"
     xmlns:gs="http://www.opengis.net/pidflo/1.0"
     serviceBoundary="value"
     recursive="true">
     <ext:region>true</ext:region>
     <ext:limit>20</ext:limit>
     <location id="6020688f1ce1896d" profile="geodetic-2d">
       <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326">
         <gml:pos>37.775 -122.422</gml:pos>
         <gs:radius uom="urn:ogc:def:uom:EPSG::9001">
            100
         </gs:radius>
       </gs:Circle>
     </location>
     <service>urn:service:food.pizza</service>
   </findService>


   Figure 7: A <findService> geodetic query with the new <limit> and
   <region> elements.  This query is a combination of 'N nearest' and
   'served by' queries (a hypothetical service URN of
   "urn:service:food.pizza" is used)

5.5.  The <serviceLocation> Element in Responses

   It is important for the LoST client to know the location of a point
   of interest so that distance, route and other metrics can be
   computed.  We introduce a new element, namely <serviceLocation>.  The
   <serviceLocation> element contains the location of a point of
   service.  When it is used, it MUST be contained in a <mapping>
   element.  In responses such as <findServiceResponse> [RFC5222], a
   list of service URIs, each with its own <serviceLocation> element,
   SHOULD be returned.  The order of service URIs in the list is not
   relevant.

   The <serviceLocation> element has one single attribute, 'profile', in
   order to specify the profile used.  Both civic and geodetic profiles
   can be used.  The geodetic profiles SHOULD be used in order to
   compute distance, route and other metrics as at some point computing
   such metrics would require geocoding of the civic address in geodetic
   coordinates.  Because of this, the position specified in
   <serviceLocation> with a geodetic profile SHOULD be represented by
   using the <Point> element.  The <Point> element is described in
   Section 12.2 of [RFC5222] and in Section 5.2.1 of [RFC5491].  Figure



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   8 shows a <findServiceResponse> answer containing two location-to-
   service-URI mappings.

   [NOTE: The <locationUsed> element cannot be extended for this purpose
   as it is defined outside of the <mapping> element.  In particular, in
   a response the <locationUsed> element is always one, while the number
   of service URIs is typically more than one.]

   There are situations, however, in which it is helpful to include a
   civic address together with the geodetic coordinates of a point of
   service.  Usually, databases already contain the civic address of
   points of interest and for devices with limited capabilities it is
   not always possible to perform decoding of geocoordinates in order to
   determine the civic address.  Because of this, including also the
   civic address in a response can be useful.  In order to do this, we
   use a civic profile for the <serviceLocation> element and specify the
   POI civic address in a <civicAddress> element contained in the
   <serviceLocation> element.  The basic civic location profile is
   defined in Section 12.3 of [RFC5222].

   As per [RFC5139] it is RECOMMENDED to use multiple <serviceLocation>
   elements when multiple forms of service location are available and
   also, it is RECOMMENDED to provide a geodetic form whenever possible.
   When multiple <serviceLocation> elements are present for one POI, all
   of them MUST be contained in the same <mapping> element that is, the
   <mapping> element for that POI.  Figure 8 shows a
   <findServiceResponse> answer with both geodetic and civic locations.


      <?xml version="1.0" encoding="UTF-8"?>
      <findServiceResponse
        xmlns="urn:ietf:params:xml:ns:lost1"
        xmlns:ext="urn:ietf:params:xml:ns:lost-ext"
        xmlns:gml="http://www.opengis.net/gml">
        <mapping
          expires="2007-01-01T01:44:33Z"
          lastUpdated="2006-11-01T01:00:00Z"
          source="authoritative.example"
          sourceId="7e3f40b098c711dbb6060800200c9a66">
          <displayName xml:lang="it">
            Che bella pizza e all' anima da' pizza da Toto'
          </displayName>
          <service>urn:service:food.pizza</service>
          <uri>sip:chebella@example.com</uri>
          <uri>xmpp:chebella@example.com</uri>
          <serviceNumber>2129397040</serviceNumber>
          <ext:serviceLocation profile="geodetic-2d">
            <gml:Point id="point1" srsName="urn:ogc:def:crs:EPSG:4326">



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              <gml:pos>33.665 -112.432</gml:pos>
            </gml:Point>
          </ext:serviceLocation>
          <ext:serviceLocation profile="civic">
            <civicAddress
                xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
                <country>US</country>
                <A1>New York</A1>
                <A3>New York</A3>
                <A6>Broadway</A6>
                <HNO>321</HNO>
                <PC>10027</PC>
            </civicAddress>
          </ext:serviceLocation>
        </mapping>
        <mapping
          expires="2007-01-01T01:44:33Z"
          lastUpdated="2006-11-01T01:00:00Z"
          source="authoritative.example"
          sourceId="7e3f40b098c711dbb6060800200c9b356">
          <displayName xml:lang="en">
            King Mario's Pizza
          </displayName>
          <service>urn:service:food.pizza</service>
          <uri>sip:marios@example.com</uri>
          <uri>xmpp:marios@example.com</uri>
          <serviceNumber>2129397157</serviceNumber>
          <ext:serviceLocation profile="geodetic-2d">
            <gml:Point id="point1" srsName="urn:ogc:def:crs:EPSG:4326">
              <gml:pos>33.683 -112.412</gml:pos>
            </gml:Point>
          </ext:serviceLocation>
          <ext:serviceLocation profile="civic">
            <civicAddress
                xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
                <country>US</country>
                <A1>New York</A1>
                <A3>New York</A3>
                <A6>Amsterdam Avenue</A6>
                <HNO>123</HNO>
                <PC>10027</PC>
            </civicAddress>
          </ext:serviceLocation>
        </mapping>
        <path>
          <via source="resolver.example"/>
          <via source="authoritative.example"/>
        </path>



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        <locationUsed id="6020688f1ce1896d"/>
      </findServiceResponse>


   Figure 8: A <findServiceResponse> answer


6.  Emergency Services

   The LoST extensions defined in this document SHOULD NOT be used when
   routing emergency sessions as there may be LoST servers that do not
   support these extensions.

   Figure 9 shows a <findService> query for emergency services as
   defined in [RFC5222].  As we can see, in such query both the <region>
   element and the <limit> element are missing.  According to the LoST
   extensions defined in this document, when the <region> element is
   missing its value defaults to true and the query is a "served by"
   query (see Section 5.3).  When the <limit> element is missing it
   means that no limit is specified that is, the LoST server can return
   any number of results (see Section 5.4).  This behavior is consistent
   with [RFC5222] so that PSAPs are selected according to their service
   area and when user location overlaps multiple service areas, the LoST
   server MAY return multiple PSAPs.

   The LoST extensions defined in this document are consistent with the
   behavior defined in [RFC5222] and as such they do not modify LoST
   behavior for emergency services.


   <?xml version="1.0" encoding="UTF-8"?>
      <findService
        xmlns="urn:ietf:params:xml:ns:lost1"
        xmlns:p2="http://www.opengis.net/gml"
        serviceBoundary="value"
        recursive="true">

        <location id="6020688f1ce1896d" profile="geodetic-2d">
          <p2:Point id="point1" srsName="urn:ogc:def:crs:EPSG::4326">
             <p2:pos>37.775 -122.422</p2:pos>
          </p2:Point>
        </location>
        <service>urn:service:sos.police</service>

      </findService>






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   Figure 9: A <findService> geodetic query for emergency services

   Unlike emergency services, where information such as service
   boundaries of PSAPs and locations of fire stations does not change
   very often, if at all, non-emergency services have information that
   may become inaccurate quickly.  This is something implementers should
   take into account when designing applications for non-emergency
   location-based services.


7.  Relax NG Schema

   This section provides the Relax NG schema of LoST extensions in the
   compact form.  The verbose form is included in Section 9.


   namespace a = "http://relaxng.org/ns/compatibility/annotations/1.0"
   default namespace ns1 = "urn:ietf:params:xml:ns:lost-ext"

   ##
   ##    Extensions to the Location-to-Service Translation (LoST)
   ##    Protocol

   ##
   ##    LoST Extensions define three new elements: limit, region and
   ##    serviceLocation.
   ##
   start =
     limit
     | region
     | serviceLocation

   ##
   ##    A limit to the number of returned results.
   ##
   div {
     limit=
       element limit {
         xsd:positiveInteger
       }
   }

   ##
   ##   A boolean variable to request a search
   ##   based on either service areas or distance.
   ##
   ##   NOTE: The W3C XML Schema has two different
   ##         lexical representations for boolean:



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   ##         '1' or 'true' vs. '0' or 'false'.
   ##
   div {
     region=
       element region {
         xsd:boolean
       }
   }

   ##
   ##    Location Information
   ##
   div {
     locationInformation =
       extensionPoint+,
       attribute profile { xsd:NMTOKEN }?
   }

   ##
   ##    Location Information about the returned point
   ##    of service.
   ##
   div {
     serviceLocation=
       element serviceLocation { locationInformation }+
   }

   ##
   ##    Patterns for inclusion of elements from schemas in
   ##    other namespaces.
   ##
   div {

     ##
     ##    Any element not in the LoST Extensions
     ##    namespace.
     ##
     notLostExt = element * - (ns1:* | ns1:*) { anyElement }

     ##
     ##    A wildcard pattern for including any element
     ##    from any other namespace.
     ##
     anyElement =
       (element * { anyElement }
        | attribute * { text }
        | text)*




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     ##
     ##    A point where future extensions
     ##    (elements from other namespaces)
     ##    can be added.
     ##
     extensionPoint = notLostExt*
   }



8.  Security Considerations

   The overall LoST architecture and framework are defined in [RFC5582].
   All LoST queries for both emergency and non-emergency services, if
   not cached, are sent from the LoST client to a first-hop LoST server.
   In [RFC5582] terminology, a LoST client is called Seeker and the
   first-hop LoST server is called Resolver (for more rigorous
   definitions please refer to [RFC5582]).  The Resolver will contact
   other LoST servers and eventually an authoritative LoST server will
   be found.  A response will then be sent back to the Seeker.

   When considering both emergency and non-emergency services there is
   the possibility of the Resolver getting overloaded by non-emergency
   services queries, thus being unable to process emergency-service
   queries.  Such a situation can be addressed in more than one way.

   The obvious way to address this problem is to properly dimension the
   LoST servers so to take into account also traffic for non-emergency
   services.  Given that the LoST server is an enhanced HTTP server,
   properly dimensioning a deployment of LoST servers should not be very
   difficult to accomplish.

   The same security considerations as in [RFC5222] apply.  In
   particular, in order to maintain integrity and confidentiality of
   requests and responses, Transport Layer Security (TLS) MUST be
   implemented and SHOULD be used as described in Sections 1, 14 and 18
   of [RFC5222].


9.  IANA Considerations

9.1.  LoST Extensions Relax NG Schema Registration

   URI: urn:ietf:params:xml:schema:lost-ext

   Registrant Contact: Andrea G. Forte, forte@att.com; Henning
   Schulzrinne, hgs@cs.columbia.edu




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   Relax NG Schema: The Relax NG schema to be registered is contained in
   Section 6.  Its first line is

   default namespace ns1 = "urn:ietf:params:xml:ns:lost-ext"

   and its last line is

   }

9.2.  LoST Extensions Namespace Registration

   URI: urn:ietf:params:xml:ns:lost-ext

   Registrant Contact: Andrea G. Forte, forte@att.com; Henning
   Schulzrinne, hgs@cs.columbia.edu

   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>
     <meta http-equiv="content-type"
           content="text/html;charset=iso-8859-1"/>
     <title>LoST Extensions Namespace</title>
   </head>
   <body>
     <h1>Namespace for LoST Extensions</h1>
     <h2>urn:ietf:params:xml:ns:lost-ext</h2>
   <p>See <a href="http://www.rfc-editor.org/rfc/rfcXXXX.txt">
      RFCXXXX</a>.</p>
   </body>
   </html>
   <!-- [[NOTE TO RFC-EDITOR: Please replace all instances of RFCXXXX
           with the number of the published document and remove this
           note.]] -->
   END



10.  Non-Normative RELAX NG Schema in XML Syntax


<?xml version="1.0" encoding="UTF-8"?>
   <grammar ns="urn:ietf:params:xml:ns:lost-ext"
           xmlns="http://relaxng.org/ns/structure/1.0"



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           xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
           datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">

           <start>
       <a:documentation>
         Extensions to the Location-to-Service Translation (LoST)
         Protocol.
         LoST Extensions define three new elements: limit, region and
         serviceLocation.
       </a:documentation>
       <choice>
         <ref name="limit"/>
         <ref name="region"/>
         <ref name="serviceLocation"/>
       </choice>
           </start>

     <div>
       <a:documentation>
         A limit to the number of returned results.
       </a:documentation>

       <define name="limit">
         <element name="limit">
           <data type="positiveInteger"/>
         </element>
       </define>
     </div>

    <div>
      <a:documentation>
        A boolean variable to request a search
        based on either service areas or distance.
      </a:documentation>

      <define name="region">
        <element name="region">
          <data type="boolean"/>
        </element>
      </define>
    </div>

     <div>
       <a:documentation>
         Location Information
       </a:documentation>

       <define name="locationInformation">



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         <oneOrMore>
           <ref name="extensionPoint"/>
         </oneOrMore>
         <optional>
           <attribute name="profile">
             <data type="NMTOKEN"/>
           </attribute>
         </optional>
       </define>
     </div>

     <div>
       <a:documentation>
         Location Information about the returned point of service.
       </a:documentation>

       <define name="serviceLocation">
         <element name="serviceLocation">
             <ref name="locationInformation"/>
         </element>
       </define>
     </div>

     <div>
       <a:documentation>
         Patterns for inclusion of elements from schemas in
         other namespaces.
       </a:documentation>

       <define name="notLostExt">
         <a:documentation>
           Any element not in the LoST Extensions namespace.
         </a:documentation>
         <element>
           <anyName>
             <except>
               <nsName ns="urn:ietf:params:xml:ns:lost-ext"/>
               <nsName/>
             </except>
           </anyName>
           <ref name="anyElement"/>
         </element>
       </define>

       <define name="anyElement">
         <a:documentation>
           A wildcard pattern for including any element
           from any other namespace.



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         </a:documentation>
         <zeroOrMore>
           <choice>
             <element>
               <anyName/>
               <ref name="anyElement"/>
             </element>
             <attribute>
               <anyName/>
             </attribute>
             <text/>
           </choice>
         </zeroOrMore>
       </define>

       <define name="extensionPoint">
         <a:documentation>
           A point where future extensions
           (elements from other namespaces)
           can be added.
         </a:documentation>
         <zeroOrMore>
           <ref name="notLostExt"/>
         </zeroOrMore>
       </define>
     </div>

  </grammar>



11.  Acknowledgments

   We would like to thank Shida Schubert for reviewing an early version
   of the LoST Extensions document.  Also, we would like to thank some
   of the members of the ECRIT working group.  In particular, we thank
   Martin Thomson, Richard L. Barnes and Robert Sparks for the overall
   feedback and for their comments on how non-emergency services may
   affect the provisioning of emergency services.


12.  Normative References

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

   [RFC5222]  Hardie, T., Newton, A., Schulzrinne, H., and H.
              Tschofenig, "LoST: A Location-to-Service Translation



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              Protocol", RFC 5222, August 2008.

   [RFC5139]  Thomson, M. and J. Winterbottom, "Revised Civic Location
              Format for Presence Information Data Format Location
              Object (PIDF-LO)", RFC 5139, February 2008.

   [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.

   [RFC5582]  Schulzrinne, H., "Location-to-URL Mapping Architecture and
              Framework", RFC 5582, September 2009.


Authors' Addresses

   Andrea G. Forte
   AT&T
   Security Research Center
   33 Thomas Street
   New York, NY  10007
   USA

   Email: forte@att.com


   Henning Schulzrinne
   Columbia University
   Department of Computer Science
   1214 Amsterdam Avenue, MC 0401
   New York, NY  10027
   USA

   Email: hgs@cs.columbia.edu
















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