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ECRIT                                                           B. Rosen
Internet-Draft
Updates: 5222 (if approved)                                  R. Marshall
Intended status: Standards Track                               J. Martin
Expires: 5 September 2022                                    Comtech TCS
                                                            4 March 2022


     A LoST extension to return complete and similar location info
                  draft-ietf-ecrit-similar-location-19

Abstract

   This document describes an extension to the LoST protocol of RFC 5222
   that allows additional civic location information to be returned in a
   <findServiceResponse>.  This extension supports two use cases: First,
   when the input location is valid but lacks some Civic Address
   elements, the LoST server can provide a completed form.  Second, when
   the input location is invalid, the LoST server can identify one or
   more feasible ("similar") locations.  This extension is applicable
   when the location information in the <findService> request uses the
   Basic Civic profile as described in RFC 5222 or another profile whose
   definition provides instructions concerning its use with this
   extension.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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 5 September 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview of Returned Location Information . . . . . . . . . .   4
   4.  Returned Location Information . . . . . . . . . . . . . . . .   8
   5.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Complete Location returned for Valid Location . . . . . .  10
     5.2.  Similar Location returned for Invalid Location  . . . . .  12
   6.  XML Schema  . . . . . . . . . . . . . . . . . . . . . . . . .  14
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     8.1.  XML Schema Registration . . . . . . . . . . . . . . . . .  16
     8.2.  LoST-RLI Namespace Registration . . . . . . . . . . . . .  17
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   The LoST protocol [RFC5222] supports the validation of civic location
   information sent in a <findService> request, by providing a set of
   validation result status indicators in the response.  The current
   usefulness of the supported XML elements <valid>, <invalid>, and
   <unchecked> is limited.  They each provide an indication of validity
   for any one location element as a part of the whole civic address,
   but this is insufficient in providing either the complete set of
   civic address elements that the LoST server contains, or of providing
   alternate suggestions (hints) as to which civic address is intended
   for use.

   Whether the queried civic location is valid but missing information,
   or invalid due to missing or wrong information, this document
   provides a mechanism to return a complete set of civic address
   elements.






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   This enhancement to the validation feature within LoST is required by
   systems that rely on accurate location for processing.  Use of this
   enhancement increases the likelihood that incorrect or incomplete
   civic location will be updated.  One such use case is that of
   location-based emergency calling.  The use of this protocol extension
   facilitates the timely correction of errors, and allows LoST clients
   to be more easily provisioned with complete address information.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The following terms are defined in this document:

   Location:  The term Location is in general used to refer to either a
      civic location or a geodetic location.  In the context of this
      document, location is restricted to civic locations.

   Geodetic Location:  a geographic coordinate set of values that
      describes a point within a defined geographic datum.  For example,
      a referenced latitude/longitude coordinate pair (2D), or latitude,
      longitude, and altitude (3D).  Note: geodetic location is defined
      here for context, but is not used elsewhere within this document.

   Civic Location:  A set of Civic Address Elements as defined in
      [RFC5139] that are used in conjunction with each other, and in
      accordance with a known ruleset to designate a specific place
      within a country.

   Civic Address:  The term Civic Address is used interchangeably with
      the term Civic Location within this document.

   Civic Address Element:  The term Civic Address Element is used within
      this document to indicate any individual XML element used within
      the <civicAddress> type defined in [RFC5139], including elements
      used at the extension point therein such as those defined in
      [RFC6848] and elsewhere.  This term also includes the reference to
      such elements by qualified name as defined within the
      <locationValidation> element in [RFC5222].

   Invalid Location:  A Civic Location that, when included in a LoST
      query with 'validateLocation' set, will receive a response having
      one or more Civic Address Elements in the <invalid> list.  Note
      that it is also possible that the location information submitted



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      is so inaccurate that location validation cannot be performed, and
      the LoST server may return a <notFound> or <locationInvalid>
      error.  In this document, the term Invalid Location only refers to
      a case where the LoST server returns one or more elements in the
      <invalid> list; the error conditions are not considered.

   Valid Location:  A Civic Location that, when included in a LoST query
      with 'validateLocation' set, will receive a response having all
      Civic Address Elements in the <valid> or <unchecked> lists.

   Incomplete Location:  "A Civic Location that the LoST server
      considers valid but which omits one or more Civic Address Elements
      that the LoST server considers necessary or helpful.

   Complete Location:  A Civic Location that was considered by the LoST
      server to be an Incomplete Location but that with the addition of
      one or more Civic Address Elements is considered complete by the
      LoST server.

   Similar Location:  A suggested civic location that is similar to an
      Invalid Location which was used in a LoST query, but which has one
      or more elements added, modified, or removed such that the
      suggested location is a Valid Location.  Similar Location may be
      returned when the input location is invalid.

   Returned Location Information:  A set of civic locations returned in
      a LoST response.

3.  Overview of Returned Location Information

   This document describes an extension to LoST [RFC5222] that allows
   additional location information to be returned in the
   <locationValidation> element of a <findServiceResponse>.  This
   extension has two different use cases: First, when the input location
   is incomplete but the LoST server can identify the intended unique
   address, and second, when the input location is invalid and the LoST
   server can identify one or more likely intended locations.  This
   extension is applicable when the location information in the
   <findService> request is in the Basic Civic profile as described in
   [RFC5222] or in another profile whose definition provides
   instructions concerning its use with this extension.  As of this
   document's publication, no such additional location profiles have
   been defined, so this document describes the returned location
   extension using the Basic Civic profile.  In addition, the following
   restriction is imposed: A server MUST NOT include Returned Location
   Information using a location profile that differs from the profile of
   the location used to answer the query and, by extension, MUST NOT
   include Returned Location Information using a location profile that



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   was not used by the client in the request.

   When a LoST server is asked to validate a civic location, its goal is
   to take the set of Civic Address Elements provided as the location
   information in the LoST request, and find a unique location in its
   database that matches the information in the request.  Uniqueness
   might not require values for all possible elements in the Civic
   Address that the database might hold.  Further, the input location
   information might not represent the form of location the users of the
   LoST service prefer to have.  As an example, there are LoST Civic
   Address Elements that could be used to define a postal location,
   suitable for delivery of mail as well as a municipal location
   suitable for responding to an emergency call.  While the LoST server
   might be able to determine the location from the postal elements
   provided, the emergency services would prefer that the municipal
   location be used for any subsequent emergency call.  Since validation
   is often performed well in advance of an end user placing an
   emergency call, if the LoST server could return the preferred form of
   location (or more properly in this example, the municipal elements in
   addition to the postal elements), those elements could be stored in a
   client application such as a Location Information Server (LIS) and
   used in a later emergency call.

   In addition, this document describes the reuse of the same mechanism,
   but for a different purpose: to supply similar location information
   in the case where a LoST server response includes one or more Civic
   Address Elements marked as invalid, indicating an Invalid Location
   used in the query.  In this case, the response contains one or more
   suggested alternative Valid Locations.

   In a LoST <findServiceResponse> indicating a Valid Location
   (Section 2) i.e., containing the <locationValidation> element with no
   elements listed as invalid, the LoST server can use this extension to
   include additional location information in a <locationValidation>
   element.  As an example, a query contains <HNO> (house number), <RD>
   (road name) <A3> (city), <A1> (state/province) but not <POD> (Post-
   Directional).  In this example, there is no street with just the
   street name, all streets have a post-directional.  However, the LoST
   server is able to uniquely locate the intended address and thus
   consider the queried location Valid, as there is only one street with
   the street name and house number in the city that it could be.  As
   the queried location is missing the post-directional element, a more
   strict entity might consider it Invalid (e.g., during a subsequent
   query) or worse, the lack of a Post-Directional element might cause
   confusion and delay an emergency response.  The server can use this
   extension to supply the missing post-directional element <POD> in a
   <completeLocation> element within the <locationValidation> element.




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   In another example, the civic location in a request might lack <A2>
   (county) and <PC> (Postal Code) Civic Address Elements.  In this
   example, too, the LoST server is able to uniquely locate the intended
   address and consider the location <Valid>, but other entities
   involved in a subsequent emergency call might find it helpful to have
   the additional Civic Address Elements.  The LoST server can use this
   extension to supply the missing <A2> and <PC> Civic Address Elements.

   Since [RFC5222] does not have a way for this additional location
   information to be returned in the <findServiceResponse>, this
   document extends the LoST protocol so that it can include a
   <completeLocation> element within the <locationValidation> element of
   the <findServiceResponse> message, allowing for the representation of
   complete location information.

   An example showing complete location information supplied:

   Input address:

      6000 15th Avenue
      Leets, WA US

   Complete Location:

      6000 15th Avenue Northwest
      Leets, WA 98105 US

   The information provided in the request may be enough to identify a
   unique location in the LoST server, but that may not be the location
   intended by the end user.  The <completeLocation> information may
   alert the user to a mismatch between the provided location
   information and the unique location the server interpreted that
   information to identify.

   The other use case for this extension is when the <findService>
   request contains an Invalid Location.  When a LoST server returns a
   response to a <findService> request that contains a set of Civic
   Address Elements with one or more listed as invalid, this extension
   allows the server to include in the <locationValidation> element one
   or more locations that might be the intended location.











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   In the example cited above, policy at the LoST server might deem a
   missing <A3> element as being invalid, even if the location
   information in the request is sufficient to identify a unique
   address.  In this case, the missing element is listed in the
   <invalid> list, and a <similarLocation> element could be returned in
   the response showing a complete civic location that includes the
   missing <A3> element, just as in the above example the missing <A3>
   element is included in a <completeLocation> element.

   As another example of the use of <similarLocation>, consider the
   results based on a similar data set as used above, but where the
   <HNO>, <RD>, <STS>, <A1>, and <A3> Civic Address Elements are not
   sufficient to locate a unique address, resulting in an invalid
   location response.  Because the LoST server contains additional civic
   address elements which, had they been included in the query, would
   have resulted in a uniquely identifiable location, the server can
   include one or more <similarLocation> elements containing the
   supplied Civic Address Elements plus the omitted ones.  Since
   [RFC5222] does not have a way for this additional location
   information to be returned in the <findServiceResponse>, this
   document extends [RFC5222] so that the LoST <locationValidation>
   element of the <findServiceResponse> can include one or more
   <similarLocation> elements representing similar civic locations.

   To show this, suppose that a slightly modified version of the above
   address is sent within a Lost <findService> request:

   Input address:

      6000 15th Avenue North
      Leets, WA US

   This time we make the assumption that the address is deemed invalid
   by the LoST server because there is no such thing as "15th Avenue
   North" within the LoST server's data for the city of Leets.  However,
   we also happen to know for this example that there are two addresses
   within the address dataset that are "similar", when all parts of the
   address are taken as a whole.  These similar addresses that could be
   returned to the client are as follows:

   Similar address #1:

      6000 15th Avenue Northwest
      Leets, WA 98107 US

   Similar address #2:

      6000 15th Avenue Northeast



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      Leets, WA 98105 US

   This extension allows the LoST server to include the above similar
   addresses in the response to a <findService> request with
   'validateLocaton' set to true.  Section 5 shows examples of the LoST
   request and response XML message fragments for the above valid and
   invalid scenarios, returning the complete or similar addresses
   respectively.

4.  Returned Location Information

   A LoST server implementing this extension MAY include
   <completeLocation> or <similarLocation> elements within the
   <locationValidation> portion of the <findServiceResponse>.  The
   <completeLocation> and <similarLocation> elements are of type
   "locationInformation" as defined by the LoST schema in [RFC5222].
   These elements MAY contain location information either in the Basic
   Civic profile defined in [RFC5222] or in another profile whose
   definition provides instructions concerning its use with this
   extension; this MUST be the same profile as the location in the
   query.  When used with the Basic Civic profile, these elements
   contain a <civicAddress> element as defined in [RFC5139].

   If there is at least one Civic Address Element in the <invalid> list,
   the LoST server MAY include one or more <similarLocation> element in
   the response.  If there are too many possible locations, the server
   MAY return none, or it MAY return a subset considered most likely.
   How many to return is left to the implementation of the LoST server.
   The server is unable to know what the intended location information
   was supposed to be; it is guessing.  Therefore, the correct location
   may or may not be one of the <similarLocation> elements the server
   provides, and the client cannot assume that any one of them is the
   correct location.


















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   Where a LoST server contains additional location information relating
   to the Civic Address used in a <findService> request, the
   <findServiceResponse> message MAY include a <completeLocation>
   element containing additional location information along with the
   original validated Civic Address Elements; the additional Civic
   Address Elements may be deemed by local policy as necessary to form a
   Complete Location.  The <completeLocation> element MUST NOT be
   returned in response messages where any Civic Address Elements occur
   in the invalid list of the response, or where the set of Civic
   Address Elements in the request do not identify a unique location.
   The Complete Location MUST NOT contain any elements that would be
   marked as invalid, or cause an error, if a recipient of that location
   performs a subsequent <findService> request using the Complete
   Location.  However, if a subsequent request includes the Complete
   Location, the corresponding response MAY include elements in the
   unchecked list.

   Clients can control the return of additional location information by
   including the optional 'returnAdditionalLocation' attribute with
   possible values 'none', 'similar', 'complete' or 'any'.  The value
   'none' means to not return additional location information, 'similar'
   and 'complete' mean to only return the respective type of additional
   location information (if the server could send any) and 'any' means
   to include Similar and/or Complete Location (if the server could send
   any).  If the request includes this attribute, the server MUST NOT
   send location information contravening the client's request.
   Omitting this attribute in the request is equivalent to including it
   with the value 'none'.

   The server may determine that there are many possible Similar
   Locations and decide not to send them all.  The number of Similar
   Locations sent is entirely up to the server.  The server MAY include
   a 'similarLocationsOmitted' attribute which contains a non-zero
   integer indicating the minimum number of Similar Locations not
   included in the response.  There may be more than the indicated
   similar locations available in the data held by the server, but no
   mechanism to request more Similar Locations is provided.

   Clients MAY ignore the location information this extension defines.
   The information is optional to send, and optional to use.  In the
   case where the location information in the request was valid, this
   extension does not change the validity.  In the case where the
   location information in the request is invalid, but alternate
   location information is returned, the original location remains
   invalid, and the LoST server does not change the mapping response
   other than optionally including the information defined by this
   extension.




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   The <completeLocation> and <similarLocation> elements use the
   <locationInformation> element from [RFC5222] updated by
   [I-D.ietf-ecrit-lost-planned-changes], including the 'profile'
   attribute, which is useful if the request contains location
   information in a profile other than the 'civic' profile.  The
   'profile' attribute MUST be included in both the request and the
   response and MUST be the same profile in both.

5.  Examples

5.1.  Complete Location returned for Valid Location

   This example is based on the example request above; the LoST server
   considered the location in the query to be valid but missing some
   Civic Address elements, so in the Returned Location Information in
   the <findServiceResponse>, the server includes a <completeLocation>
   element supplying the omitted Civic Address elements <A2>, <PC>, and
   <PCN>.

      <!-- =====Request=================================== -->


      <findService xmlns="urn:ietf:params:xml:ns:lost1"
        xmlns:rli="urn:ietf:params:xml:ns:lost-rli1"
        validateLocation="true" rli:returnAdditionalLocation="any">

        <location id="587cd3880" profile="civic">
          <civicAddress
            xmlns="urn:ietf:params:mxl:ns:pidf:geopriv10:civicAddr">

            <country>US</country>
            <A1>WA</A1>
            <A3>Leets</A3>
            <RD>15th</RD>
            <STS>Avenue</STS>
            <POD>Northwest</POD>
            <HNO>6000</HNO>

          </civicAddress>
        </location>

        <service>urn:service:sos</service>

      </findService>


      <!-- =====Response================================== -->




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      <findServiceResponse
        xmlns="urn:ietf:params:xml:ns:lost1"
        xmlns:rli="urn:ietf:params:xml:ns:lost-rli1"
        xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">

        <mapping
          expires="NO-CACHE"
          lastUpdated="2006-11-01T01:00:00Z"
          source="authoritative.example"
          sourceId="8799e346000098aa3e">

          <displayName xml:lang="en">Leets 911</displayName>
          <service>urn:service:sos</service>
          <uri>sip:leets-911@example.com</uri>
          <serviceNumber>911</serviceNumber>

        </mapping>

        <locationValidation>

          <valid>ca:country ca:A1 ca:A3 ca:RD ca:STS ca:POD ca:HNO
          </valid>
          <invalid></invalid>
          <unchecked></unchecked>

          <rli:completeLocation profile="civic"><!--completed address-->
            <ca:civicAddress>
              <ca:country>US</ca:country>
              <ca:A1>WA</ca:A1>
              <ca:A2>SHOWAK COUNTY</ca:A2>
              <ca:A3>LEETS</ca:A3>
              <ca:RD>15TH</ca:RD>
              <ca:STS>AVENUE</ca:STS>
              <ca:POD>NORTHWEST</ca:POD>
              <ca:HNO>6000</ca:HNO>
              <ca:PC>98106</ca:PC>
              <ca:PCN>LEETS</ca:PCN>
            </ca:civicAddress>

        </rli:completeLocation>

      </locationValidation>

        <path>
          <via source="authoritative.example"/>
        </path>

        <locationUsed id="587cd3880"/>



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      </findServiceResponse>


      <!-- =============================================== -->

5.2.  Similar Location returned for Invalid Location

   The following example shows two Similar Locations returned in a
   <findServiceResponse> message when the original input address is
   considered invalid, in this example because the LoST server needed
   the omitted POD data to match a unique address.

   <!-- =====Request=================================== -->


      <findService xmlns="urn:ietf:params:xml:ns:lost1"
        xmlns:rli="urn:ietf:params:xml:ns:lost-rli1"
        validateLocation="true"
        rli:returnAdditionalLocation="any">

        <location id="587cd3880" profile="civic">
           <civicAddress
            xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">

              <country>AU</country>
              <A1>QLD</A1>
              <A3>PIMPANA</A3>
              <RD>SHIRLEY</RD>
              <STS>STREET</STS>
              <HNO>98</HNO>
              <PC>4209</PC>
              <PCN>PIMPANA</PCN>

          </civicAddress>
        </location>

        <service>urn:service:sos</service>

      </findService>

      <!-- =====Response=================================== -->


      <findServiceResponse
        xmlns="urn:ietf:params:xml:ns:lost1"
        xmlns:rli="urn:ietf:params:xml:ns:lost-rli1"
        xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">




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        <mapping
          expires="NO-CACHE"
          lastUpdated="2006-11-01T01:00:00Z"
          source="authoritative.example"
          sourceId="8799e346000098aa3e">

          <displayName xml:lang="en">Australian 000</displayName>
          <service>urn:service:sos</service>
          <uri>sip:000@example.com</uri>
          <serviceNumber>000</serviceNumber>

        </mapping>

        <locationValidation similarLocationsOmitted="5">

          <valid>ca:country ca:A1 ca:A3 ca:STS ca:RD</valid>
          <invalid>ca:POD</invalid>
          <unchecked>ca:HNO ca:PC ca:PCN</unchecked>

          <rli:similarLocation profile="civic"><!--similar location-->
            <ca:civicAddress>  <!-- similar address #1 -->
              <ca:country>AU</ca:country>
              <ca:A1>QLD</ca:A1>
              <ca:A3>PIMPANA</ca:A3>
              <ca:RD>SHIRLEY</ca:RD>
              <ca:STS>STREET</ca:STS>
              <ca:POD>NORTH</ca:POD>
              <ca:HNO>98</ca:HNO>
              <ca:PC>4209</ca:PC>
              <ca:PCN>PIMPANAS</ca:PCN>
            </ca:civicAddress>
          </rli:similarLocation>
          <rli:similarLocation profile="civic" >
            <ca:civicAddress>  <!-- similar address #2 -->
            <ca:country>AU</ca:country>
            <ca:A1>QLD</ca:A1>
            <ca:A3>PIMPANA</ca:A3>
            <ca:RD>SHIRLEY</ca:RD>
            <ca:STS>STREET</ca:STS>
            <ca:POD>SOUTH</ca:POD>
            <ca:HNO>98</ca:HNO>
            <ca:PC>4209</ca:PC>
            <ca:PCN>PIMPANAS</ca:PCN>

            </ca:civicAddress>
        </rli:similarLocation>

      </locationValidation>



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        <path>
          <via source="authoritative.example"/>
        </path>

        <locationUsed id="587cd3880"/>

      </findServiceResponse>


      <!-- =============================================== -->

6.  XML Schema

   This section provides the schema of the LoST extensions, based on the
   schema in [I-D.ietf-ecrit-lost-planned-changes]




































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   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
              xmlns:lost1="urn:ietf:params:xml:ns:lost1"
              xmlns="urn:ietf:params:xml:ns:lost-rli1"
              targetNamespace="urn:ietf:params:xml:ns:lost-rli1"
              elementFormDefault="qualified">
        <!-- Import base Lost -->
        <xs:import namespace="urn:ietf:params:xml:ns:lost1"/>
   <!-- extend findService by placing the following
       at the extensionPoint
       in the included commonRequestPattern: -->
         <xs:attribute name="returnAdditionalLocation" use="optional">
          <xs:simpleType>
             <xs:restriction base="xs:token">
               <xs:enumeration value="none"/>
               <xs:enumeration value="similar"/>
               <xs:enumeration value="complete"/>
               <xs:enumeration value="any"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>


         <!-- extend locationValidation by placing the following
                  at the extensionPoint -->
         <xs:group>
           <xs:choice minOccurs="0">
             <xs:element name="similarLocation"
                       type="lost1:locationInformation"
                       minOccurs="1" maxOccurs="unbounded" />
             <xs:element name="completeLocation"
                       type="lost1:locationInformation"/>
           </xs:choice>
         </xs:group>

         <!-- and also at the locationValidation extensionPoint -->
         <xs:attribute name="similarLocationsOmitted" use="optional">
           <xs:simpleType>
             <xs:restriction base="xs:integer">
                 <xs:minInclusive value="1"/>
                 </xs:restriction>
           </xs:simpleType>
         </xs:attribute>

   </xs:schema>






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7.  Security Considerations

   As this document defines extensions to [RFC5222], the Security
   Considerations of that document apply here.

   Whether the input to the LoST server is a Valid or Invalid Location,
   the LoST server ultimately determines what it considers to be a Valid
   Location.  Even in the case where the input location is valid, the
   requester still might not actually understand where that location is.
   For this kind of Valid Location use case, this extension will
   typically return more location information than what the requester
   started with, which might reveal to the requester additional
   information (additional CAtypes) about the location.  While this is
   very desirable in some scenarios such as supporting an emergency
   call, it might not be as desirable for other services.  Individual
   LoST server implementations should consider the risk of releasing
   more detail versus the value in doing so.  Generally, supplying more
   information (CAtypes) is not considered to be a significant problem
   because the requester has to already have enough information for the
   location to be considered valid, which in most cases is enough to
   uniquely locate the address.  Providing more CAtypes generally
   doesn't actually reveal anything more.  When Invalid Locations are
   submitted, this extension allows the LoST response to include
   locations that are similar to what was input, again resulting in more
   information provided in the response than was sent in the request.
   LoST server implementations should evaluate the particular use cases
   where this extension is supported, and weigh the risks around its
   use.  Many services available today via the Internet offer similar
   features, such as "did you mean" or address completion, so this
   capability is not introducing any fundamentally new security concern.

   The similar location service could be misused to attempt to enumerate
   the entire database by running a high volume of invalid or partial
   queries.  The LoST server can limit the volume of similar locations
   it returns.  It can also authenticate queries and limit the service
   to known queriers

8.  IANA Considerations

8.1.  XML Schema Registration

   IANA is requested to register the following in the "schema" sub-
   registry of the IETF XML Registry per [RFC3688].








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      URI:  urn:ietf:params:xml:schema:lost-rli1

      Registrant Contact:  IETF ECRIT Working Group, Brian Rosen
         (br@brianrosen.net).

      XML Schema: The XML schema to be registered is contained
         in Section 6.

8.2.  LoST-RLI Namespace Registration

   IANA is requested to register the following in the "ns" sub-registry
   of the IETF XML registry per [RFC3553].

      URI:  urn:ietf:params:xml:ns:lost-rli1

      Registrant Contact:  IETF ECRIT Working Group, Brian Rosen
         (br@brianrosen.net).

      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 Returned Location Information Namespace</title>
   </head>
   <body>
     <h1>Namespace for LoST Returned Location Information extension</h1>
     <h2>urn:ietf:params:xml:ns:lost-rli1</h2>
   <p>See <a href="http://www.rfc-editor.org/rfc/rfc????.txt">
      RFC????</a>.</p>
   </body>
   </html>
   END

9.  References

9.1.  Normative References









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   [I-D.ietf-ecrit-lost-planned-changes]
              Rosen, B., "Validation of Locations Around a Planned
              Change", Work in Progress, Internet-Draft, draft-ietf-
              ecrit-lost-planned-changes-05, 11 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-ecrit-lost-
              planned-changes-05.txt>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3553]  Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
              IETF URN Sub-namespace for Registered Protocol
              Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
              2003, <https://www.rfc-editor.org/info/rfc3553>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC5139]  Thomson, M. and J. Winterbottom, "Revised Civic Location
              Format for Presence Information Data Format Location
              Object (PIDF-LO)", RFC 5139, DOI 10.17487/RFC5139,
              February 2008, <https://www.rfc-editor.org/info/rfc5139>.

   [RFC5222]  Hardie, T., Newton, A., Schulzrinne, H., and H.
              Tschofenig, "LoST: A Location-to-Service Translation
              Protocol", RFC 5222, DOI 10.17487/RFC5222, August 2008,
              <https://www.rfc-editor.org/info/rfc5222>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2.  Informative References

   [RFC6848]  Winterbottom, J., Thomson, M., Barnes, R., Rosen, B., and
              R. George, "Specifying Civic Address Extensions in the
              Presence Information Data Format Location Object (PIDF-
              LO)", RFC 6848, DOI 10.17487/RFC6848, January 2013,
              <https://www.rfc-editor.org/info/rfc6848>.

Authors' Addresses







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   Brian Rosen
   470 Conrad Dr
   Mars, PA 16046
   United States of America
   Email: br@brianrosen.net


   Roger Marshall
   Comtech TCS
   2401 Elliott Avenue
   2nd Floor
   Seattle, WA 98121
   United States of America
   Email: roger.marshall@comtechtel.com


   Jeff Martin
   Comtech TCS
   2401 Elliott Avenue
   2nd Floor
   Seattle, WA 98121
   United States of America
   Email: jeff.martin@comtechtel.com




























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