ECRIT                                                          T. Hardie
Internet-Draft                                            Qualcomm, Inc.
Intended status: Standards Track                               A. Newton
Expires: September 5, 2007                                     SunRocket February 11, 2008                                TranTech, Inc.
                                                          H. Schulzrinne
                                                     Columbia U. University
                                                           H. Tschofenig
                                                  Nokia Siemens Networks GmbH & Co KG
                                                           March 4,
                                                         August 10, 2007

            LoST: A Location-to-Service Translation Protocol
                      draft-ietf-ecrit-lost-05.txt
                      draft-ietf-ecrit-lost-06.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document describes an XML-based protocol for mapping service
   identifiers and geodetic or civic location information to service
   contact URIs.  In particular, it can be used to determine the
   location-appropriate PSAP for emergency services.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology and Requirements Notation  . . . . . . . . . . . .  6
   3.  Overview of Protocol Usage . . . . . . . . . . . . . . . . . .  7
   4.  LoST servers Servers and Their Resolution  . . . . . . . . . . . . . .  9
   5.  The <mapping> Element  . . . . . . . . . . . . . . . . . . . . 10
     5.1.  The Mapping Data Source:  'source', 'sourceId' and
           'lastUpdated' Attributes . . . . . . . . . . . . . . . . . 10
     5.2.  Mapping Validity:  The 'expires' Attribute . . . . . . . . . . . . 10
     5.3.  Describing the Service with the <displayName> Element  . . 11
     5.4.  The Mapped Service:  the <service> Element . . . . . . . . 11
     5.5.  Defining the Service Region with the <serviceBoundary>
           Element  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     5.6.  Service Boundaries by Reference: the
           <serviceBoundaryReference> Element . . . . . . . . . . . . 12
     5.7.  The Service Number Number:  the <serviceNumber> Element . . . . . . . . . . . . . . . . 13
     5.8.  Service URLs: the <uri> Element  . . . . . . . . . . . . . 13
   6.  Path of a Request: the <path> Element  . . . . . . . . . . . . . . 14
   7.  Identifying the Location Element Used for Mapping:
       <locationUsed> . . . . . . . . . . . . . . . . . . . . . . . . 15
   8.  Mapping a Location and Service to URLs: <findService>  . . . . 15
     7.1. 16
     8.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 15
     7.2. 16
     8.2.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . 15
       7.2.1. 16
       8.2.1.  Example Using Geodetic Coordinates . . . . . . . . . . 15
       7.2.2. 16
       8.2.2.  Civic Address Mapping Example  . . . . . . . . . . . . 16
     7.3. 17
     8.3.  Components of the <findService> Request  . . . . . . . . . 18
       7.3.1. 19
       8.3.1.  The <location> Element . . . . . . . . . . . . . . . . 18
       7.3.2. 19
       8.3.2.  Identifying the Service:  The <service> Element  . . . 19
       7.3.3. 20
       8.3.3.  Recursion and Iteration  . . . . . . . . . . . . . . . 19
       7.3.4. 20
       8.3.4.  Service Boundary . . . . . . . . . . . . . . . . . . . 19
       7.3.5. 20
       8.3.5.  Requesting Civic Location Validation . . . . . . . . . 19
     7.4. 20
     8.4.  Components of the Mapping Response
           <findServiceResponse>  . . . . . . . . . . . . . . . . . . 21
       7.4.1. 22
       8.4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . 21
       7.4.2. 22
       8.4.2.  Civic Address Validation:  the
               <locationValidation> Element . . . . . . . . . . . . . 22
   8. 23
   9.  Retrieving the Service Boundary via <getServiceBoundary> . . . 23
   9. 24
   10. List Services: <listServices>  . . . . . . . . . . . . . . . . 26
   10. 27
   11. List Services By Location: <listServicesByLocation>  . . . . . 27
   11. 28
   12. Location Profiles  . . . . . . . . . . . . . . . . . . . . . . 29
     11.1. 30
     12.1. Location Profile Usage . . . . . . . . . . . . . . . . . . 30
     11.2. 31
     12.2. Two Dimensional Geodetic Profile . . . . . . . . . . . . . 33
     11.3. 34
     12.3. Basic Civic Profile  . . . . . . . . . . . . . . . . . . . 34
   12. 35
   13. Errors, Warnings, and Redirects  . . . . . . . . . . . . . . . 35
     12.1. 37
     13.1. Errors . . . . . . . . . . . . . . . . . . . . . . . . . . 35
     12.2. 37
     13.2. Warnings . . . . . . . . . . . . . . . . . . . . . . . . . 36
     12.3. 39
     13.3. Redirects  . . . . . . . . . . . . . . . . . . . . . . . . 37
   13. 40
   14. LoST Transport . . . Transport: HTTP . . . . . . . . . . . . . . . . . . . . . 38
   14. 42
   15. Relax NG Schema  . . . . . . . . . . . . . . . . . . . . . . . 39
   15. 43
   16. Internationalization Considerations  . . . . . . . . . . . . . 46
   16. 50
   17. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 47
     16.1. 51
     17.1. U-NAPTR Registrations  . . . . . . . . . . . . . . . . . . 47
     16.2. 51
     17.2. Content-type registration for 'application/lost+xml' . . . 47
     16.3. 51
     17.3. LoST Relax NG Schema Registration  . . . . . . . . . . . . 49
     16.4. 53
     17.4. LoST Namespace Registration  . . . . . . . . . . . . . . . 49
     16.5. 53
     17.5. LoST Location Profile Registry . . . . . . . . . . . . . . 50
   17. 54
   18. Security Considerations  . . . . . . . . . . . . . . . . . . . 51
   18. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 52 55
   19. Open Issues  . . Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 54 56
   20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55 58
     20.1. Normative References . . . . . . . . . . . . . . . . . . . 55 58
     20.2. Informative References . . . . . . . . . . . . . . . . . . 56 59
   Appendix A.  Non-Normative RELAX NG Schema in XML Syntax . . . . . 57 60
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 70 74
   Intellectual Property and Copyright Statements . . . . . . . . . . 71 75

1.  Introduction

   Numerous techniques have been specified for

   Protocols such as NAPTR records and the discovery of Service Location Protocol
   (SLP) can be used to discover servers
   for offering a particular service, including NAPTR records, SVRLOC and similar
   protocols. service.
   However, there are for an important class of services where the appropriate specific
   service instance that is to be connected to depends both on the identity of the service and the
   geographic location of the entity that needs to reach it.  An example of this is emergency  Emergency
   telecommunications
   services, where services are an important example; here, the
   service instance is a Public Safety Answering Point (PSAP) that has
   jurisdiction over the location of the user making the call.  Here, the  The
   desired PSAP isn't necessarily the one that is topologically or even
   line-of-sight closest to the caller; rather, it is the one that
   serves the callers location based on
   geopolitical jurisdictional boundaries.  For this reason, the selected service
   instance is a function of location and the desired service.

   This document describes a protocol for mapping a service identifier
   (service URNs) [9] and location information compatible with PIDF-LO
   [6], namely revised civic location information [10] and a subset of
   the PIDF-LO profile [13] and consequently with the Geo-Shapes [12]
   defined for GML [12]) [11]) to one or more service URL. URLs.  Example service
   URL schemes include sip [14], xmpp [15], and tel [16].  While the
   initial focus is on providing mapping functions for emergency
   services, it is likely that the protocol is applicable to any other
   service URN. URNs.  For example, in the United States, the "2-1-1" and
   "3-1-1" service numbers follow a similar location-to-
   service location-to-service behavior
   as emergency services.

   This document names this protocol "LoST", for Location-to-Service
   Translation.  LoST Satisfies the requirements [18] for mapping
   protocols.  LoST provides a number of operations, centered around
   mapping locations and service URNs to service URLs and associated
   information.  LoST mapping queries can contain either civic or
   geodetic location information.  For civic addresses, LoST can
   indicate which parts of the civic address are known to be valid or
   invalid, thus providing address validation (see validation, as described in Section
   3.5 of [18]
   for a description of validation). [18].  LoST indicates errors in the location data to
   facilitate debugging and proper user feedback, but also provides
   best-effort answers.

   LoST queries can be resolved recursively or iteratively.  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").

   As defined in this document, LoST messages are carried in HTTP and
   HTTPS protocol exchanges, facilitating use of TLS for protecting the
   integrity and confidentiality of requests and responses.

   This document focuses on the description of the protocol between the
   mapping client and the mapping server.  Other functions, such as
   discovery of mapping servers, data replication and the overall
   mapping server architecture are described in a separate document
   [19].

   The query message carries location information and a service
   identifier encoded as a Uniform Resource Name (URN) (see [9]) from
   the LoST client to the LoST server.  The LoST server uses its
   database to map the input values to one or more Uniform Resource
   Identifiers (URI) and returns those URIs along with optional
   information, such as hints about the service boundary, in a response
   message to the LoST client.  If the server cannot resolve the query
   itself, it may in turn query another server or return the address of
   another LoST server, identified by a LoST server name.  In addition
   to the mapping function described in Section 7, 8, the protocol also
   allows to retrieve the service boundary (see Section 8) 9) and to list
   the services available for a particular location (see Section 10) 11) or
   supported by a particular server (see Section 9). 10).

2.  Terminology and 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 [1].

   This document uses the following terms:

   Mapping:  Mapping is a process that takes a location and a service
      identifier as inputs and returns one or more URIs.  Those URIs that can
      either point to a host providing that service or acting as an intermediary to
      establish communication with a host that in
      turn routes the request to the serving entity. final destination.  This definition
      is a generalization of the term "mapping" as used in [18], because
      of the potential for
      LoST to can be used for non-emergency services.

   LoST Client and Server:

      "LoST client" is the role played by an entity that client:  A host acts as a LoST client if it sends LoST query
      messages and receives LoST response messages.  "LoST server"
      is the role played by an entity that

   LoST server:  A host acts as a LoST server if it receives LoST query
      messages and sends LoST response messages.  In recursive
      operation, the same entity may play be both roles.  This document also uses the term
      "authoritative server" to designate an entity that acts in the a client and a server.

   Authoritative LoST server:  An authoritative server role acts only as a
      server and successfully resolves the input location and service
      identifier to a URI or set of URIs.

   Service Boundary: boundary:  A service boundary is circumscribes the boundary or set of boundaries of a
      geographic region, respectively set of geographic regions, region within
      which all locations will map to the same service URI or set of URIs for
      a given service.  A service boundary may consist of several non-
      contiguous geometric shapes.

   Validation:

      The term "validation" as used in this document is a concrete
      realization of describes the term behavior defined as "location
      validation" as defined in Section 3.5 of [18].

   Additional emergency service terminology can be found in [18].

3.  Overview of Protocol Usage

   The LoST protocol supports the following type of queries and
   responses:

   <findService> and <findServiceResponse>

      This message pattern allows to perform retrieve

      A LoST client retrieves contact URIs based on location information together with
      and a service identifier. identifier with this request and response.  The same
      query type may also ask for location validation and for service
      numbers, either integrated into combined with a mapping request or separately.
      The details can be found in Section 7 8 and Section 7.4. 8.4.

   <getServiceBoundary> and <getServiceBoundaryResponse>

      This message pattern allows query for

      A LoST client obtains a service boundary.  The
      details can be found boundary with this request and
      response, as described in Section 8. 9.

   <listServices> and <listServicesResponse>

      This message pattern enables

      With this request and response, a LoST client to ask can find out which
      services a LoST server
      for the services it supports.  The details can be found supports, as described in Section 9. 10.

   <listServicesByLocation> and <listServicesByLocationResponse>

      This message pattern provides the

      A LoST client can determine with the this request and response which
      services
      that are available for a specific location region.  The details
      can be found in  Section 10. 11
      describes the details.

   LoST clients may initiate any of the above queries at any time.
   Among the common triggers are:

   1.  When the client initially starts up or attaches to a network. network;

   2.  When  when the client detects that its location has changed
       sufficiently that it is outside the bounds of the service region. region;

   3.  An incoming  when a SIP message arrives at a SIP proxy in a location-based routing
       scenario that requires a routing decision to be made. performing location-
       based call routing;

   4.  When  when cached mapping information has expired. expired;

   5.  When  when invoking a particular service.  At that time, a client may
       omit requests for service boundaries or other auxiliary
       information.

   A service-specific Best Current Practice (BCP) document, such as
   [20], governs whether a client is expected to invoke the mapping
   service just before needing the service or whether to rely on cached
   answers.  Cache entries expire at their expiration time (see
   Section 5.2), or they become invalid if the caller's device moves
   beyond the boundaries of the service region.

4.  LoST servers Servers and Their Resolution

   LoST servers are identified by U-NAPTR/DDDS [11] [8] application unique
   strings, in the form of a DNS name.  An example is 'lostserver.example.com'
   'lostserver.example.com'.

   Clients need to use the U-NAPTR [11] [8] specification described below to
   obtain a URI (indicating host and protocol) for the applicable LoST
   service.  In this document, only the HTTP and HTTPS URL schemes are
   defined.  Note that the HTTP URL can be any valid HTTP URL, including
   those containing path elements.

   The following two DNS entries show the U-NAPTR resolution for
   "example.com" to the HTTPS URL https://lostserv.example.com/secure or
   the HTTP URL http://lostserver.example.com, with the former being
   preferred.

       example.com.

       IN NAPTR 100  10   "u"    "LoST:https"
            "!.*!https://lostserver.example.com/secure!"  ""

       IN NAPTR 200  10   "u"    "LoST:http"
            "!.*!http://lostserver.example.com!"  ""

   Clients learn the LoST server's host name by means beyond the scope
   of this specification, such as SIP configuration and DHCP.

5.  The <mapping> Element

   The <mapping> element is the core data element in LoST, describing a
   service region and the associated service URLs.  Its attributes and
   elements are described in subsections below.

5.1.  The Mapping Data Source:  'source', 'sourceId' and 'lastUpdated'
      Attributes

   The 'source', the 'sourceId' and the 'lastUpdated' attributes
   uniquely identify a particular mapping record.  They are created by
   the authoritative source for a mapping and are never modified when a
   mapping is served from a cache.  All three attributes are REQUIRED
   for all <mapping> elements.  A receiver can replace a mapping with
   another one having the same 'source' and 'sourceId' and a more recent
   datum
   time in 'lastUpdated'.

   The 'source' attribute contains a LoST application unique string
   identifying the authoritative generator of the mapping.  See
   Section 4. mapping (Section 4).

   The 'sourceId' attribute identifies a particular mapping and contains
   an opaque token that MUST be unique among all different mappings
   maintained by the authoritative source for that particular service.
   For example, a Universally Unique Identifier (UUID) is a suitable
   format.

   The 'lastUpdated' attribute describes when a specific instance of
   mapping, identified by the combination of 'source' and 'sourceId',
   was last changed.  The contents of this attribute has the XML data
   type dateTime in its timezoned form, using canonical UTC
   representation with the letter 'Z' as the timezone indicator.

5.2.  Mapping Validity:  The 'expires' Attribute

   The 'expires' attribute contains the absolute time at which the
   mapping becomes invalid.  The contents of this attribute is a
   timezoned XML type dateTime, in canonical representation.  See
   Section 3 regarding how this value is to be utilized with a cache.
   The 'expires' attribute is REQUIRED to be included in the <mapping>
   element.

   Optionally, this attribute may contain the values of 'NO-CACHE' and
   'NO-EXPIRATION' instead of a dateTime value.  The value 'NO-CACHE' is
   an indication that the mapping should not be cached.  The value of
   'NO-EXPIRATION' is an indication that the mapping does not expire.

   On occasion, a server may be forced to return an expired mapping if
   it cannot reach the authoritative server or the server fails to
   return a usable answer.  Clients and servers MAY cache the mapping so
   that they have at least some information available.  Caching servers
   that have such stale information SHOULD re-attempt the query each
   time a client requests a mapping.  Since the expired mapping will be
   returned to the client as a non-error/non-warning response it is the
   responsibility of the client to check the 'expires' attribute
   associated with mapping data returned in a LoST response to detemine determine
   whether the mapping is fresh.

5.3.  Describing the Service with the <displayName> Element

   Zero or more <displayName> elements describe the service with a
   string that is suitable for display to human users, each annotated
   with the 'xml:lang' attribute that contains a language tag to aid in
   the rendering of text.

5.4.  The Mapped Service:  the <service> Element

   The mandatory <service> element identifies the service for which this
   mapping applies.  Two cases need to be distinguished when the LoST
   server sets the <service> element in the response message:

   1.  If the requested service, identified by the service URN [9] in
       the <service> element of the request, exists for the location
       indicated, then the LoST server puts copies the service URN from the
       request into the <service> element.

   2.  If, however, the requested service, identified by the service URN
       [9] in the <service> element in the request, does not exist for
       the location indicated, the server can either return an
       <serviceNotImplemented> (Section 12.1) 13.1) error or can provide an
       alternate service that approximates the desired service for that
       location.  In the latter case, the server MUST include a
       <service> element with the alternative service URN.  The choice
       of service URN is left to local policy, but the alternate service
       should be able to satisfy the original service request.

   The <service> element is optional but may also be required if the
   mapping is to be digitally signed.

5.5.  Defining the Service Region with the <serviceBoundary> Element

   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_.  The service region can be indicated by value or by
   reference (see Section 5.6).  If a client moves outside the service
   area and wishes to obtain current service data, it sends a new query
   with its current location.  The service region is described by value
   in one or more <serviceBoundary> elements, each formatted according
   to a different specific location profile, identified by the 'profile' atribute attribute
   (see Section 11). 12). serviceBoundary elements formatted according to
   different location profiles are alternative representations of the
   same area, not additive to one another; this allows a client
   understanding only one of the profile types to be sure it has a
   complete view of the serviceBoundary.  Within a serviceBoundary
   element there may, however, be multiple locations which _are_
   additive; this is necessary because some serviceBoundary areas could
   not be easily expressed with a single shape or civic location.  If
   included in a response, the <serviceBoundary> element MUST contain at
   least one service boundary that uses the same profile as the request.  The client only processes the first element
   that it can understand according to its list of supported location
   profiles.  Thus, elements with geospatial coordinates are alternative
   descriptions of the same service region, not additive geometries.

   A service boundary is requested by the client (using client, using the
   'serviceBoundary' attribute in the request with the value set to
   "value").

   A response MAY contain more than one <serviceBoundary> element with
   profile 'civic'.  Each <serviceBoundary> element describes a set of
   civic addresses that fall within the service boundary, namely all
   addresses that textually match the civic address elements provided,
   regardless of the value of other address elements.  A location falls
   within the mapping's service boundary if it matches any of the
   <serviceBoundary> elements.
   "value".

5.6.  Service Boundaries by Reference: the <serviceBoundaryReference>
      Element

   Since geodetic service boundaries may contain thousands of points and
   can thus be quite large, clients may opt wish to conserve bandwidth and
   request by
   requesting a reference to the service boundary instead of the value
   described in Section 5.5.  The identifier of the service boundary is
   returned as an attribute of the <serviceBoundaryReference> element,
   along with a LoST application unique string (see Section 4)
   identifying the server from where it can be retrieved.  The actual
   value of the service boundary is then retrieved with the
   getServiceBoundary (Section 8) 9) request.

   A reference to a service boundary is requested by the client (using
   the 'serviceBoundary' attribute in the request with the value set to
   "reference").  A LoST server may decide, based on local policy, to
   return the service boundary per value or to omit the
   <serviceBoundaryReference> element in the response.

   The identifier is a random token with at least 128 bits of entropy
   and can be assumed to be globally unique.  It uniquely references a
   particular boundary.  If the boundary changes, a new identifier MUST
   be chosen.  Because of these properties, a client receiving a mapping
   response can simply check if it already has a copy of the boundary
   with that identifier.  If so, it can skip checking with the server
   whether the boundary has been updated.  Since service boundaries are
   likely to remain unchanged for extended periods of time, possibly
   exceeding the normal lifetime of the service URL, this approach
   avoids unnecessarily refreshing the boundary information just because
   the the remainder of the mapping has become invalid.

5.7.  The Service Number Number:  the <serviceNumber> Element

   The service number is returned in the optional <serviceNumber>
   element.  It contains a string of digits, * and # that a user on a
   device with a 12-key dial pad could use to reach that particular
   service.

5.8.  Service URLs: the <uri> Element

   The response returns the service URLs in one or more <uri> elements.
   The URLs MUST be absolute URLs.  The ordering of the URLs has no
   particular significance.  Each URL scheme MUST only appear at most
   once, but it is permissible to include both secured and regular
   versions of a protocol, such as both 'http' and 'https' or 'sip' and
   'sips'.

6.  Path of a Request: the <path> Element

   To prevent loops and to allow tracing of request and response paths,
   all requests that allow recursion include a <path> element that
   contains one or more <via> elements, each possessing an attribute
   containing a LoST application unique string (see Section 4).  The
   order of <via> elements corresponds to the order of LoST servers,
   i.e., the first <via> element identifies the server that initially
   received the request from the client issuing the request.  The <via>
   element is inserted logically on receipt of the request, so that
   every server in a recursive query operation is included in the <path>
   element.

   The server that answers the request instead of forwarding it, such as
   the authoritative server, copies the <path> element verbatim into the
   response.  The <path> element is not modified in responses as the
   responses traverses the server chain back to the querying client.

   If a query is answered iteratively, the querier includes all servers
   that it has already contacted.

   When a cached mapping is returned then the <path> element cached
   together with the mapping is returned.

   The example in Figure 5 indicates that the answer was given to the
   client by the LoST server at esgw.ueber-110.de.example, which got the
   answer from the (authoritative) LoST server at
   polizei.muenchen.de.example.

7.  Mapping a Location and Service to URLs: <findService>

7.1.  Overview

   The <findService> query constitutes  Identifying the core Location Element Used for Mapping: <locationUsed>

   Several of the LoST
   functionality, mapping civic requests can provide one or geodetic locations to URLs and more <location> elements,
   among which the server gets to choose.  It is useful for the client
   to be able to determine which one was actually used in producing the
   result.  For that purpose, the <location> tag MUST contain an 'id'
   attribute that uniquely identifies the <location> element.  The
   format of the identifier is left to the client; it could, for
   example, use a hash of the location information.  The server returns
   the identifier for the <location> element it used in the
   <locationUsed> tag.

8.  Mapping a Location and Service to URLs: <findService>

8.1.  Overview

   The <findService> query constitutes the core of the LoST
   functionality, mapping civic or geodetic locations to URLs and
   associated data.  After giving an example, we enumerate the elements
   of the query and response.

7.2.

8.2.  Examples

7.2.1.

8.2.1.  Example Using Geodetic Coordinates

   The following is an example of mapping a service to a location using
   geodetic coordinates, for the service associated with the police
   (urn:service:sos.police).

   <?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>

                 Figure 2: A <findService> geodetic query

   Given the query above, a server would respond with a service, and
   information related to that service.  In the example below, the
   server has mapped the location given by the client for a police
   service to the New York City Police Deparment, Department, instructing the
   client that it may contact them via the URIs "sip:nypd@example.com"
   and "xmpp:nypd@example.com".  The server has also given the client a
   geodetic, two-dimensional boundary for this service.  The mapping was
   last updated on November 1, 2006 and expires on January 1, 2007.  If
   the client's location changes beyond the given service boundary or
   the expiration time has been reached, it may want to requery for this
   information, depending on the usage environment of LoST.

   <?xml version="1.0" encoding="UTF-8"?>
   <findServiceResponse xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/gml">
     <mapping
       expires="2007-01-01T01:44:33Z"
       lastUpdated="2006-11-01T01:00:00Z"
       source="authoritative.example"
       sourceId="7e3f40b098c711dbb6060800200c9a66" version="1">
       sourceId="7e3f40b098c711dbb6060800200c9a66">
       <displayName xml:lang="en">
         New York City Police Department
       </displayName>
       <service>urn:service:sos.police</service>
       <serviceBoundary profile="geodetic-2d">
         <p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
           <p2:exterior>
             <p2:LinearRing>
               <p2:pos>37.775 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4194</p2:pos>
             </p2:LinearRing>
           </p2:exterior>
         </p2:Polygon>
       </serviceBoundary>
       <uri>sip:nypd@example.com</uri>
       <uri>xmpp:nypd@example.com</uri>
       <serviceNumber>911</serviceNumber>
     </mapping>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
       <via source="authoritative.example"/>
     </path>
     <locationUsed id="6020688f1ce1896d"/>
   </findServiceResponse>

             Figure 3: A <findServiceResponse> geodetic answer

7.2.2.

8.2.2.  Civic Address Mapping Example

   The following is an example of mapping below shows how to map a service to a location much like
   the example in Section 7.2.1, 8.2.1, but using civic address location
   information.  In this example, the client requests the service
   associated with police (urn:service:sos.police) along with a specific
   civic address (house number 6 on a street named Otto-Hahn-Ring in
   Munich, Germany).

   <?xml version="1.0" encoding="UTF-8"?>
   <findService xmlns="urn:ietf:params:xml:ns:lost1"
     recursive="true" serviceBoundary="value">
     <location id="627b8bf819d0bad4d" profile="civic">
       <civicAddress
         xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
         <country>Germany</country>
         <A1>Bavaria</A1>
         <A3>Munich</A3>
         <A6>Otto-Hahn-Ring</A6>
         <HNO>6</HNO>
         <PC>81675</PC>
       </civicAddress>
     </location>
     <service>urn:service:sos.police</service>
   </findService>

               Figure 4: A <findService> civic address query

   Given the query above, a server would respond with a service, and
   information related to that service.  In the example below, the
   server has mapped the location given by the client for a police
   service to the Muenchen Polizei-Abteilung, instructing the client
   that it may contact them via the URIs sip:munich-police@example.com
   and xmpp:munich-police@example.com.  The server has also given the
   client a civic address boundary (the city of Munich) for this
   service.  The mapping was last updated on November 1, 2006 by the
   authoritative source "polizei.muenchen.de.example" and expires on
   January 1, 2007.  This instructs the client to requery for the
   information if its location changes beyond the given service boundary
   (i.e., beyond the city of Munich) or after January 1, 2007.

   <?xml version="1.0" encoding="UTF-8"?>
   <findServiceResponse xmlns="urn:ietf:params:xml:ns:lost1">
     <mapping
       expires="2007-01-01T01:44:33Z"
       lastUpdated="2006-11-01T01:00:00Z"
       source="esgw.ueber-110.de.example"
       sourceId="e8b05a41d8d1415b80f2cdbb96ccf109" version="1" >
       sourceId="e8b05a41d8d1415b80f2cdbb96ccf109">
       <displayName xml:lang="de">
         Muenchen Polizei-Abteilung
       </displayName>
       <service>urn:service:sos.police</service>
       <serviceBoundary
         profile="urn:ietf:params:lost:location-profile:basic-civic">
         <civicAddress
           xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
           <country>Germany</country>
           <A1>Bavaria</A1>
           <A3>Munich</A3>
           <PC>81675</PC>
         </civicAddress>
       </serviceBoundary>
       <uri>sip:munich-police@example.com</uri>
       <uri>xmpp:munich-police@example.com</uri>
       <serviceNumber>110</serviceNumber>
     </mapping>
     <path>
       <via source="esgw.ueber-110.de.example"/>
       <via source="polizei.muenchen.de.example"/>
     </path>
     <locationUsed id="627b8bf819d0bad4d"/>
   </findServiceResponse>

          Figure 5: A <findServiceResponse> civic address answer

7.3.

8.3.  Components of the <findService> Request

   The <findService> request includes attributes that govern whether the
   request is handled iteratively or recursively, whether location
   validation is performed and which elements may be contained in the
   response.

7.3.1.

8.3.1.  The <location> Element

   The <findService> query communicates location information using one
   or more <location> elements, which MUST conform to a location profile
   (see Section 11). 12).  There MUST NOT be more than one location element
   for each distinct location profile.  The order of location objects elements
   is significant; the server uses the first location object element where it
   understands the location profile.

7.3.2.

8.3.2.  Identifying the Service:  The <service> Element

   The type of service desired is specified by the <service> element.
   It contains service URNs from the registry established in [9].

7.3.3.

8.3.3.  Recursion and Iteration

   LoST can operate in either recursive or iterative mode, on a request-
   by-request basis.  In recursive mode, the LoST server initiates
   queries on behalf of the requester and returns the result to the
   requester.

   In iterative mode, the server contacted returns a redirection
   response indicating the next server to be queried. queried if the server
   contacted cannot provide an answer itself.

   For the queries defined in this document, only LoST <findService> and
   <listServicesByLocation> queries can be recursive, as indicated by
   the 'recursive' attribute.  A value of "true" indicates a recursive
   query, with the default being "false" when the attribute is omitted.
   Regardless of the attribute, a server MAY always answer a query by
   providing a LoST application unique string (see Section 4), i.e.,
   indirection, however, it MUST NOT recurse if the attribute is
   "false".

7.3.4.

8.3.4.  Service Boundary

   LoST <mapping> elements can describe the service boundary either by
   value or by reference.  Returning a service boundary reference is
   generally more space-efficient for geospatial (polygon) boundaries
   and if the boundaries change rarely, but does incur an additional
   <getServiceBoundary> request.  The querier can express a preference
   for one or the other modality with the 'serviceBoundary' attribute in
   the <findService> request, but the server makes the final decision as
   to whether to return a reference or a value.

7.3.5.

8.3.5.  Requesting Civic Location Validation

   Civic address validation is requested by setting the optional
   attribute 'validateLocation' to true.  If the attribute is omitted,
   it is assumed to be false.  The response is described in
   Section 7.4.2. 8.4.2.  The example in Figure 6 demonstrates address
   validation, omitting
   validation.  If the standard response elements. server chooses a geodetic location among the
   locations provided in a request, the attribute is ignored.

   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     recursive="true"
     validateLocation="true"
     serviceBoundary="value">
     <location id="627b8bf819d0bad4d" profile="civic">
       <civicAddress
         xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
         <country>DE</country>
         <A1>Bavaria</A1>
         <A3>Munich</A3>
         <A6>Otto-Hahn-Ring</A6>
         <HNO>6</HNO>
         <PC>81675</PC>
       </civicAddress>
     </location>
     <service>urn:service:sos.police</service>
   </findService>

      Figure 6: A <findService> query with address validation request
   <?xml version="1.0" encoding="UTF-8"?>
   <findServiceResponse xmlns="urn:ietf:params:xml:ns:lost1">
     <mapping
       expires="2007-01-01T01:44:33Z"
       lastUpdated="2006-11-01T01:00:00Z"
       source="authoritative.example"
       sourceId="4db898df52b84edfa9b6445ea8a0328e"
       version="1" >
       sourceId="4db898df52b84edfa9b6445ea8a0328e">
       <displayName xml:lang="de">
         Muenchen Polizei-Abteilung
       </displayName>
       <service>urn:service:sos.police</service>
       <serviceBoundary profile="civic">
         <civicAddress
           xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
           <country>Germany</country>
           <A1>Bavaria</A1>
           <A3>Munich</A3>
           <PC>81675</PC>
         </civicAddress>
       </serviceBoundary>
       <uri>sip:munich-police@example.com</uri>
       <uri>xmpp:munich-police@example.com</uri>
       <serviceNumber>110</serviceNumber>
     </mapping>
     <locationValidation>
       <valid>country A1 A3 A6</valid>
       <invalid>PC</invalid>
       <unchecked>HNO</unchecked>
     </locationValidation>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
       <via source="authoritative.example"/>
     </path>
     <locationUsed id="627b8bf819d0bad4d"/>
   </findServiceResponse>

     Figure 7: A <findServiceResponse> message with address validation
                                information

7.4.

8.4.  Components of the Mapping Response <findServiceResponse>

7.4.1.

8.4.1.  Overview

   Mapping responses consist of the <mapping> element (Section 5)
   describing the mapping itself, possibly followed by warnings
   (Section 12.2), 13.2), location validation information (Section 7.4.2), 8.4.2), and
   an indication of the path (Section 6) the response has taken.

7.4.2.

8.4.2.  Civic Address Validation:  the <locationValidation> Element

   A server can indicate in its response which civic address elements it
   has recognized as valid, which ones it has ignored and which ones it
   has checked and found to be invalid.  The server SHOULD include this
   information if the 'validateLocation' attribute in the request was
   true but local policy at the server may allow this information to be
   omitted.  Each element contains a list of tokens separated by white
   space, enumerating the civic location lables labels used in child elements
   of the <civicAddress> element.  The <valid> element enumerates those
   civic address elements that have been recognized as valid by the LoST
   server and that have been used to determine the mapping.  The
   <unchecked> elements enumerates the civic address elements that the
   server did not check and that were not used in determining the
   response.  The <invalid> element enumerate civic address elements
   that the server attempted to check, but that did not match the other
   civic address elements found in the <valid> list.  Civic location
   tokens that are neither listed in the <valid>, the <invalid> and the
   <unchecked> element belong to the class of unchecked tokens.

   Note that the same address can yield different responses if parts of
   the civic address contradict each other.  For example, if the postal
   code does not match the city, local server policy determines whether
   the postal code or the city is considered valid.  The mapping
   naturally corresponds to the valid elements.

   The example (Figure 6) shown in Figure 6 and in Figure 7 indicates that the
   tokens 'country', 'A1', 'A3', and 'A6' have been validated by the
   LoST server.  The server considered the postal code 81675 in the <PC>
   element as not valid for this location.

8.  The 'HNO' token belongs to
   the class of unchecked location tokens.

9.  Retrieving the Service Boundary via <getServiceBoundary>

   As discussed in Section 5.5, the <findServiceResponse> can return a
   globally unique identifier in the 'serviceBoundary' attribute that
   can be used to retrieve the service boundary, rather than returning
   the boundary by value.  This is shown in the example in Figure 8. 8 and
   Figure 9.  The client can then retrieve the boundary using the
   <getServiceBoundary> request and obtains the boundary in the
   <getServiceBoundaryResponse>, illustrated in the example in
   Figure 10.  The client issues the request to the server identified in
   the 'server' attribute of the <serviceBoundaryReference> element.
   These requests are always directed to the authoritative server and do
   not recurse.

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

    Figure 8: <findService> request and response with service boundary
                                 reference
   <?xml version="1.0" encoding="UTF-8"?>
   <findServiceResponse xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/gml">
     <mapping
       expires="2007-01-01T01:44:33Z"
       lastUpdated="2006-11-01T01:00:00Z"
       source="authoritative.example"
       sourceId="7e3f40b098c711dbb6060800200c9a66"
       version="1">
       sourceId="7e3f40b098c711dbb6060800200c9a66">
       <displayName xml:lang="en">
         New York City Police Department
       </displayName>
       <service>urn:service:sos.police</service>
       <serviceBoundaryReference
         source="authoritative.example"
         key="7214148E0433AFE2FA2D48003D31172E" />
       <uri>sip:nypd@example.com</uri>
       <uri>xmpp:nypd@example.com</uri>
       <serviceNumber>911</serviceNumber>
     </mapping>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
       <via source="authoritative.example"/>
     </path>
     <locationUsed id="6020688f1ce1896d"/>
   </findServiceResponse>

       Figure 9: <findServiceResponse> message with service boundary
                                 reference

   <?xml version="1.0" encoding="UTF-8"?>
   <getServiceBoundary xmlns="urn:ietf:params:xml:ns:lost1"
       key="7214148E0433AFE2FA2D48003D31172E"/>

    Figure 10: Requesting a service boundary with <getServiceBoundary>

   The <getServiceBoundary> request may also be used to retrieve service
   boundaries that are expressed as civic addresses, as illustrated in
   Figure 11.

   <?xml version="1.0" encoding="UTF-8"?>
   <getServiceBoundaryResponse
     xmlns="urn:ietf:params:xml:ns:lost1">
     <serviceBoundary profile="civic">
     <civicAddress
       xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
         <country>US</country>
         <A1>New York</A1>
         <A3>New York</A3>
       </civicAddress>
     </serviceBoundary>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
       <via source="authoritative.example"/>
     </path>
   </getServiceBoundaryResponse>

            Figure 11: Civic Address Service Boundary Response

9.

10.  List Services: <listServices>

   A LoST client can ask a LoST server for the list of services that it
   understands, primarily for diagnostic purposes.  The query does not
   contain location information, as it simply provides an indication of
   which services the server can look up, not whether a particular
   service is offered for a particular area.  Typically, only top-level
   services are included in the answer, implying support for all sub-
   services.  Since the query is answered by the queried server, there
   is no notion of recursion or indirection and no path indication.  The
   <listServicesByLocation
   <listServicesByLocation> (Section 10) 11) query below can be used to find
   out whether a particular service is offered for a specific location.
   An example request and response are shown in Figure 12.

   <?xml version="1.0" encoding="UTF-8"?>
   <listServices
     xmlns="urn:ietf:params:xml:ns:lost1">
     <service>urn:service:sos</service>
   </listServices>

                Figure 12: Example of <ListServices> query

   <?xml version="1.0" encoding="UTF-8"?>
   <listServicesResponse
    xmlns="urn:ietf:params:xml:ns:lost1">
    <serviceList>
     urn:service:sos.ambulance
     urn:service:sos.animal-control
     urn:service:sos.fire
     urn:service:sos.gas
     urn:service:sos.mountain
     urn:service:sos.marine
     urn:service:sos.physician
     urn:service:sos.poison
     urn:service:sos.police
     urn:service:sos.suicide
    </serviceList>
   </listServicesResponse>

                Figure 13: Example of <ListServiceResponse>

10.

11.  List Services By Location: <listServicesByLocation>

   A LoST client can ask a LoST server for the list of services it knows
   about for a particular area.  The <listServicesByLocation> query
   contains one or more <location> elements, each from a different
   location profile (Section 11), 12), and may contain the <service> element.
   As for <findService>, the server selects the first location element
   that has a profile the server understands and it can operate either
   recursively or iteratively; < via> <via> elements track the progress of the
   request.  By its nature, the  The query can only indicate indicates the services that a particular the server can determine,
   enumerate from within the forest structure of which it is a part.
   Because LoST does not presume a single, overarching organization of
   all possible services
   that might potential service types, there may be offered.  Unlike <ListServices>, the answer describes
   the services available at within a specific location, not just those
   understood by the server.
   geographic area which could be described by other LoST servers
   connected to other forest structures.  As an example, the emergency
   services forest for a region may be distinct from the forests that
   locate commercial services within the same region

   If the query contains the <service> element, the LoST server returns
   only immediate child services of the queried service that are
   available for the provided location.  If the <service> element is
   absent, the LoST service returns all top-level services available for
   the provided location that it knows about.

   A server responds to this query with a
   <listServicesByLocationResponse> response.  This response MAY contain
   <via> elements (see Section 6) and MUST contain a <serviceList>
   element, consisting of a whitespace-separated list of service URNs.
   The query and response are illustrated in Figure 14 and in Figure 15,
   respectively.

   <?xml version="1.0" encoding="UTF-8"?>
   <listServicesByLocation
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/gml"
     recursive="true">
     <location id="3e19dfb3b9828c3" profile="geodetic-2d">
       <p2:Point srsName="urn:ogc:def:crs:EPSG::4326">
         <p2:pos>-34.407 150.883</p2:pos>
       </p2:Point>
     </location>
     <service>urn:service:sos</service>
   </listServicesByLocation>

           Figure 14: Example of <ListServicesbyLocation> query
   <?xml version="1.0" encoding="UTF-8"?>
   <listServicesByLocationResponse
    xmlns="urn:ietf:params:xml:ns:lost1">
    <serviceList>
     urn:service:sos.ambulance
     urn:service:sos.animal-control
     urn:service:sos.fire
     urn:service:sos.gas
     urn:service:sos.mountain
     urn:service:sos.marine
     urn:service:sos.physician
     urn:service:sos.poison
     urn:service:sos.police
     urn:service:sos.suicide
    </serviceList>
    <path>
     <via source="authoritative.example"/>
     <via source="resolver.example"/>
     <via source="authoritative.example"/>
    </path>
    <locationUsed id="3e19dfb3b9828c3"/>
   </listServicesByLocationResponse>

               Figure 15: Example of <ListServices> response

11.

12.  Location Profiles

   LoST uses location information in <location> elements in requests and
   <serviceBoundary> elements in responses.  Such location information
   may be expressed in a variety of ways.  This variety can cause
   interoperability problems where a request or response contains
   location information in a format not understood by the server or the
   client, respectively.  To achieve interoperability, this document
   defines two mandatory-to-implement baseline location profiles to
   define the manner in which location information is transmitted.  It
   is possible to standardize other profiles in the future.  The two three
   baseline profiles are:

   geodetic-2d:

      a simple profile for two-dimensional geodetic location information, as
      described in Section 11.2; 12.2;

   civic:

      a profile consisting of civic address location information, as
      described in Section 11.3. 12.3.

   Requests and responses containing <location> or <serviceBoundary>
   elements MUST contain location information in exactly one of the two
   baseline profiles, in addition to zero or more additional profiles.
   The ordering of location information indicates a preference on the
   part of the sender.

   Standards action is required for defining new profiles.  A location
   profile MUST define:

   1.  The token identifying it in the LoST location profile registry;

   2.  The formal definition of the XML to be used in requests, i.e., an
       enumeration and definition of the XML child elements of the
       <location> element;

   3.  The formal definition of the XML to be used in responses, i.e.,
       an enumeration and definition of the XML child elements of the
       <serviceBoundary> element;

   4.  The declaration of whether geodetic-2d or civic is to be used as
       the baseline profile.  It is necessary to explicitly declare the
       baseline profile as future profiles may be combinations of
       geodetic and civic location information.

11.1.

12.1.  Location Profile Usage

   A location profile is identified by a token in an IANA-maintained
   registry (Section 16.5). 17.5).  Clients send location information compliant
   with a location profile, and servers respond with location
   information compliant with that same location profile.

   When a LoST client sends a <findService> request that provides
   location information, it includes one or more <location> elements.  A
   <location> element carries a mandatory an optional 'profile' attribute that
   indicates the location format of the child elements.  A client may
   obtain location information that does not conform to a profile it
   recognizes or it may not have the capability to map XML to profiles.
   In that case, a client MAY omit the profile attribute and the server
   should interpret the XML location data to the best of its ability,
   returning a "locationProfileUnrecognized" error if it is unable to do
   so.

   The concept of location profiles are described in Section 11. 12.  With
   the ability to specify more than one <location> element the client is
   able to convey location information for multiple location profiles in
   the same request.

   When a LoST server sends a response that contains location
   information, it uses the <serviceBoundary> elements much like the
   client uses the <location> elements.  Each <serviceBoundary> element
   contains location information conformant conforming to the location profile
   specified in the 'profile' attribute.  When  A response MAY contain
   multiple <location>
   elements are included then it enables mappings or boundaries for the server different <location>
   elements, subject to send location
   information compliant with multiple location profiles. the restrictions below.

   Using the location profiles defined in this document, the following
   rules insure basic interoperatiblity ensure interoperability between clients and servers:

   1.  A client MUST be capable of understanding the response for the
       baseline profiles it used in the request.

   2.  If a client sends location information conformant to any location
       profile other than geodetic-2d or civic, the ones described in this document, it MUST
       also send, in the same request, location information conformant
       to one of the baseline profiles.  Otherwise, the server might not
       be able to understand the request.

   3.  A client SHOULD MUST NOT send multiple <location> profiles of objects that are
       derived from different baseline profiles.  Or said another way,  In other words, a
       client
       should MUST only send location profiles from objects according to the same
       baseline profile in the same query. a query, but it MAY contain a location
       element following a baseline profile in addition to some other
       profile.

   4.  If a client has both location information primarily of geodetic
       nature and location information primarily of a civic nature, it should
       MUST send separate requests containing each type of location
       information.

   4.

   5.  There can only be one instance of each location profile in a
       query.

   5.

   6.  Servers MUST implement the geodetic-2d and civic profiles.

   6. all profiles described in this document.

   7.  A server uses the first-listed location profile that it
       understands and ignores the others.

   7.

   8.  If a server receives a request that only contains location
       information using profiles it does not understand, the server
       responds with a <locationProfileError> (Section 12.1).

   8. 13.1).

   9.  The <serviceBoundary> element MUST use the same location profile
       that was used to retrieve the answer and indicates which profile
       has been used with the 'profile' attribute.

   These rules enable the use of location profiles not yet specified,
   while ensuring baseline interoperability.  Take, for example, this
   scenario.  Client X has had its firmware upgraded to support the
   uber-complex-3D
   'not-yet-standardized-prism-profile' location profile.  Client X
   sends location information to Server Y, which does not understand the
   uber-complex-3D
   'not-yet-standardized-prism-profile' location profile.  If Client X
   also sends location information using the geodetic-2D baseline
   profile, then Server Y will still be able to understand the request
   and provide an understandable response, though with location
   information that might not be as precise or expressive as desired.
   This is possible because both Client X and Server Y understand the
   baseline profile.

   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/gml"
     xmlns:gml="http://www.opengis.net/gml"
     xmlns:gs="http://www.opengis.net/pidflo/1.0"
     recursive="true"
     serviceBoundary="value">
     <location profile="uber-complex-3d">
       <p2:Point id="point1" srsName="urn:ogc:def:crs:EPSG::4326">
          <p2:pos>37.775 -122.422</p2:pos>
       </p2:Point>
         <p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
           <p2:exterior>
             <p2:LinearRing>
               <p2:pos>37.775 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4194</p2:pos>
              </p2:LinearRing>
            </p2:exterior>
         </p2:Polygon>
       <p2:Point id="point1" srsName="urn:ogc:def:crs:EPSG::4326">
          <p2:pos>-122.422 37.775</p2:pos>
       </p2:Point> profile="not-yet-standardized-prism-profile">
       <gs:Prism srsName="urn:ogc:def:crs:EPSG::4979">
         <gs:base>
           <gml:Polygon>
             <gml:exterior>
               <gml:LinearRing>
                 <gml:posList>
                   42.556844 -73.248157 36.6
                   42.656844 -73.248157 36.6
                   42.656844 -73.348157 36.6
                   42.556844 -73.348157 36.6
                   42.556844 -73.248157 36.6
                 </gml:posList>
               </gml:LinearRing>
             </gml:exterior>
           </gml:Polygon>
         </gs:base>
         <gs:height uom="urn:ogc:def:uom:EPSG::9001">
           2.4
         </gs:height>
       </gs:Prism>
     </location>
     <location profile="geodetic-2d">
       <p2:Point
       <gml:Point id="point1" srsName="urn:ogc:def:crs:EPSG::4326">
          <p2:pos>37.775 -122.422</p2:pos>
       </p2:Point> srsName="urn:ogc:def:crs:EPSG:4326">
         <gml:pos>42.656844 -73.348157</gml:pos>
       </gml:Point>
     </location>
     <service>urn:service:sos.police</service>
   </findService>

    Figure 16: Example of a <findServices> query with baseline profile
                             interoperability
   <?xml version="1.0" encoding="UTF-8"?>
   <findServiceResponse
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/">
     <mapping
       expires="2007-01-01T01:44:33Z"
       lastUpdated="2006-11-01T01:00:00Z"
       source="authoritative.example"
       sourceId="cf19bbb038fb4ade95852795f045387d"
       version="1">
       sourceId="cf19bbb038fb4ade95852795f045387d">
       <displayName xml:lang="en">
         New York City Police Department
       </displayName>
       <service>urn:service:sos.police</service>
       <serviceBoundary profile="geodetic-2d">
         <p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
           <p2:exterior>
             <p2:LinearRing>
               <p2:pos>37.775 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4194</p2:pos>
             </p2:LinearRing>
           </p2:exterior>
         </p2:Polygon>
       </serviceBoundary>
       <uri>sip:nypd@example.com</uri>
     </mapping>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
       <via source="authoritative.example"/>
     </path>
     <locationUsed id="6020688f1ce1896d"/>
   </findServiceResponse>

    Figure 17: Example of a <findServiceResponse> message with baseline
                         profile interoperability

11.2.

12.2.  Two Dimensional Geodetic Profile

   The geodetic-2d "geodetic-2d" location profile is identified by geodetic-2d. "geodetic-2d".
   Clients and servers use this profile by placing a <Point> element, as the following
   location shapes into the <serviceBoundary> or into the <location>
   element (unless indicated otherwise):

   Point:

      The <Point> element is described in Section 7.2.1 5.2.1 of [13], within the <location> element. [13].
      Section
   7.2.1 5.2.1 of [13] describes shows also the specification of a <Point>
      with either a two dimensional position (latitude and longitude) or
      three dimensional position (latitude, longitude, and altitude).  A
      client MAY use the three dimensional position, and servers MAY
      interpret a three dimensional position as a two dimensional
      position by ignoring
   altitude.

   Servers use this profile by placing a <Polygon> element, as described
   in Section 7.2.2 of [13], within the altitude value.  A <Point> element is not
      placed into a <serviceBoundary> element.  This

   Polygon:

      The <Polygon> element is defined by the 'polygon' pattern in the LoST schema (see
   Section 14).

   With respect to the description described in Section 7.2.2 5.2.2 of [13] the [13].  The
      restriction to 16 points for a polygon contained in Section 7.2.2
      of [12] is not applicable to this document.  With this profile servers MUST use WGS 84 (latitude,
   longitude), i.e., the srsName set to 'urn:ogc:def:crs:EPSG::4326'
   where altitude information

   Circle:

      The <Circle> element is omitted. described in Section 5.2.3 of [13].

   Ellipse:

      The <Ellipse> element is described in Section 5.2.4 of [13].

   ArcBand:

      The orientation <ArcBand> element is described in Section 5.2.5 of [13].

   When clients place a <Polygon>, <Circle>, <Ellipse> or <ArcBand>
   element within the points <location> element then it indicates that the
   query is about any point contained in the polygon given area; it is upward normal left to
   the server to select an appropriate matching algorithm, such as described using
   computing the centroid.  A server MAY return multiple <mapping>
   elements if the polygon extends across multiple service areas.

   When geodetic location information of this location profile is placed
   in Section 7.2.2 the <serviceBoundary> element then the elements with geospatial
   coordinates are alternative descriptions of
   [13].

11.3. the same service region,
   not additive geometries.

12.3.  Basic Civic Profile

   The basic-civic location profile is identified by the token 'civic'.
   Clients use this profile by placing a <civicAddress> element, defined
   in [10], within the <location> element.

   Servers use this profile by placing a <civicAddress> element, defined
   in [10], within the <serviceBoundary> element.

12.

   A response MAY contain more than one <serviceBoundary> element with
   profile 'civic'.  Each <serviceBoundary> element describes a set of
   civic addresses that fall within the service boundary, namely all
   addresses that textually match the civic address elements provided,
   regardless of the value of other address elements.  A location falls
   within the mapping's service boundary if it matches any of the
   <serviceBoundary> elements.  Hence, a response may contain multiple
   <serviceBoundary> elements with civic and/or geodetic location
   profiles.

13.  Errors, Warnings, and Redirects

   When a LoST server cannot fulfill a request completely, it can return
   either an error or a warning, depending on the severity of the
   problem.  It returns an error element if no useful response can be
   returned for the query.  It returns a <warnings> element as part of
   another response element if it was able to respond in part, but the
   response may not be quite what the client had desired.  This document
   does not define warnings.  For both
   elements, the 'source' attribute names the server that originally
   generated the error or warning, such as the authoritative server.
   Unless otherwise noted, all elements below can be either an error or
   a warning, depending on whether a default response, such as a
   mapping, is included.

12.1.

13.1.  Errors

   LoST defines a pattern for errors, defined as <errors> elements in
   the Relax NG schema.  This pattern defines a 'message' attribute
   containing human readable text and an 'xml:lang' attribute denoting
   the language of the human readable text.  One or more such error
   elements are contained in the <errors> element.

   The following errors follow this basic pattern:

   badRequest

      The server could not parse or otherwise understand a request,
      e.g., because the XML was malformed.

   forbidden

      The server refused to send an answer.  This generally only occurs
      for recursive queries, namely if the client tried to contact the
      authoritative server and was refused.  (For HTTP as the underlying
      protocol, an HTTP 401 error would be returned.)

   internalError

      The server could not satisfy a request due to misconfiguration or
      other operational and non-protocol related reasons.

   locationProfileUnrecognized

      None of the profiles in the request were recognized by by the server
      (see Section 12).

   locationInvalid

      The geodetic or civic location in the request was invalid.  For
      example, the longitude or latitude values fall outside the
      acceptable ranges.

   SRSInvalid

      The spatial reference system (SRS) contained in the location
      element was not recognized or does not match the server
      (see Section 11). location profile.

   loop

      During a recursive query, the server was about to visit a server
      that was already in the server list in the <path> element,
      indicating a request loop.

   notFound

      The server could not find an answer to the query.

   serverError

      An answer was received from another LoST server, but it could not
      be parsed or otherwise understood.  This error occurs only for
      recursive queries.

   serverTimeout

      A time out occurred before an answer was received.

   serviceNotImplemented

      The requested service URN is not implemented and no substitution
      was available.

   An example is below:

   <?xml version="1.0" encoding="UTF-8"?>
   <errors xmlns="urn:ietf:params:xml:ns:lost1"
     source="resolver.example">
      <internalError message="Software bug." xml:lang="en"/>
   </errors>

                  Figure 18: Example of an error resonse

12.2.

13.2.  Warnings

   A response MAY contain zero or more warnings.  This pattern defines a
   'message' attribute containing human readable text and an 'xml:lang'
   attribute denoting the language of the human readable text.  One or
   more such warning elements are contained in the <warnings> element.
   To provide human readable text in an appropriate language the HTTP
   content negotiation capabilities (see Section 14) MAY be utilized by
   a server.

   This version of the specification defines the following warnings:

   locationValidationUnavailable

      The <locationValidationUnavailable> element MAY be returned when a
      server wishes to notify a client that it cannot fulfill a location
      validation request.  This warning allows a server to return
      mapping information while signalling this exception state.

   serviceSubstitution

      The <serviceSubstitution> element MAY be returned when a server
      was not able to fulfill a <findService> request for a given
      service URN.  For example, a <findService> request with the
      'urn:service:sos.police' service URN for a location in Uruguay may
      cause the LoST service to return a mapping for the
      'urn:service:sos' service URN since Uruguay does not define any make use of
      the sub-services police, fire and ambulance.  If this warning
   elements.

12.3. is
      returned then the <service> element in the response provides
      information about the service URN that refers to the mapping.

   defaultMappingReturned

      The <defaultMappingReturned> element MAY be returned when a server
      was not able to fulfill a <findService> request for a given
      location but is able to respond with a default URI.  For example,
      a nearby PSAP may be returned.

   An example of a warning is shown below:

   <?xml version="1.0" encoding="UTF-8"?>
   <findServiceResponse xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/">
     <mapping
       expires="2007-01-01T01:44:33Z"
       lastUpdated="2006-11-01T01:00:00Z"
       source="authoritative.example"
       sourceId="fb8ed888433343b7b27865aeb38f3a99">
       <displayName xml:lang="en">
         New York City Police Department
       </displayName>
       <service>urn:service:sos.police</service>
       <serviceBoundary profile="geodetic-2d">
         <p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
           <p2:exterior>
             <p2:LinearRing>
               <p2:pos>37.775 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4194</p2:pos>
             </p2:LinearRing>
           </p2:exterior>
         </p2:Polygon>
       </serviceBoundary>
       <uri>sip:nypd@example.com</uri>
     </mapping>
     <warnings source="authoritative.example">
       <defaultMappingReturned
           message="Unable to determine PSAP for the given location;
               using default PSAP"
           xml:lang="en"/>
     </warnings>
     <path>
       <via source="resolver.example"/>
       <via source="authoritative.example"/>
     </path>
   </findServiceResponse>

                 Figure 19: Example of an warning resonse

13.3.  Redirects

   A LoST server can respond indicating that the querier should redirect
   the query to another server, using the <redirect> element.  The
   element includes a 'target' attribute indicating the LoST application
   unique string (see Section 4) that the client SHOULD be contacting
   next, as well as the 'source' attribute indicating the server that
   generated the redirect response and a 'message' attribute explaining
   the reason for the redirect response.  During a recursive query, a
   server receiving a <redirect> response can decide whether it wants to
   follow the redirection or simply return the response to its upstream
   querier.

   An example is below:

   <?xml version="1.0" encoding="UTF-8"?>
   <redirect xmlns="urn:ietf:params:xml:ns:lost1"
     target="eastpsap.example"
     source="westpsap.example"
     message="We have temporarily failed over." xml:lang="en"/>

                 Figure 19: 20: Example of a redirect resonse

13. response

14.  LoST Transport Transport: HTTP

   LoST needs an underlying protocol transport mechanisms to carry
   requests and responses.  This document defines the use of LoST over
   HTTP and LoST over HTTP-over-TLS; other mechanisms are left to future
   documents.  The available transport mechanisms are determined through
   the use of the LoST U-NAPTR application.  In protocols that support
   content type indication, LoST uses the media type application/
   lost+xml.

   When using HTTP [3] and HTTP-over-TLS [4], LoST requests use the HTTP
   POST method.  All  The HTTP request MUST use the Cache-Control response
   directive "no-cache" to HTTP-level "caching even by caches that have
   been configured to return stale responses to client requests."

   All LoST responses, including those indicating a LoST warning or
   error, are applicable. carried in 2xx responses, typically 200 (OK).  Other 2xx
   responses, in particular 203 (Non-authoritative information) may be
   returned by HTTP caches that disregard the caching instructions. 3xx,
   4xx and 5xx HTTP response codes indicates that the HTTP request
   itself failed or was redirected; these responses do not contain any
   LoST XML elements.

   The HTTP URL is derived from the LoST server name via U-NAPTR
   application, as discussed above

14. above.

15.  Relax NG Schema

   This section provides the Relax NG schema used by LoST protocol in
   the compact form.  The verbose form is included in Appendix A.

namespace a = "http://relaxng.org/ns/compatibility/annotations/1.0"
default namespace ns1 = "urn:ietf:params:xml:ns:lost1"

##
##       Location-to-Service Translation Protocol (LoST)
##
##       A LoST XML instance has three request types, each with
##       a cooresponding response type: find service, list services,
##       and get service boundary.
##
start =
  findService
  | listServices
  | listServicesByLocation
  | getServiceBoundary
  | findServiceResponse
  | listServicesResponse
  | listServicesByLocationResponse
  | getServiceBoundaryResponse
  | errors
  | redirect

##
##       The queries.
##
div {
  findService =
    element findService {
      element location { locationInformation }+,
      commonRequestPattern,
      attribute validateLocation {
        xsd:boolean >> a:defaultValue [ "false" ]
      }?,
      attribute serviceBoundary {
        ("reference" | "value") >> a:defaultValue [ "reference" ]
      }?,
      attribute recursive { xsd:boolean >> a:defaultValue [ "false" ] }?
    }
  listServices = element listServices { commonRequestPattern }
  listServicesByLocation =
    element listServicesByLocation {
      element location { locationInformation }*,
      commonRequestPattern,
      attribute recursive { xsd:boolean >> a:defaultValue [ "true" ] }?
    }
  getServiceBoundary =
    element getServiceBoundary { serviceBoundaryKey, extensionPoint }
}

##
##       The responses.
##
div {
  findServiceResponse =
    element findServiceResponse {
      mapping+, locationValidation?, commonResponsePattern
    }
  listServicesResponse =
    element listServicesResponse { serviceList, commonResponsePattern }
  listServicesByLocationResponse =
    element listServicesByLocationResponse {
      serviceList, commonResponsePattern
    }
  getServiceBoundaryResponse =
    element getServiceBoundaryResponse {
      serviceBoundary, commonResponsePattern
    }
}

##
##       A pattern common to some of the queries.
##
div {
  commonRequestPattern = service, path?, extensionPoint
}

##
##       A pattern common to responses.
##
div {
  commonResponsePattern = warnings*, path, extensionPoint
}

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

##
##       Service Boundary
##
div {
  serviceBoundary = element serviceBoundary { locationInformation }+
}

##
##       Service Boundary Reference
##
div {
  serviceBoundaryReference =
    element serviceBoundaryReference {
      source, serviceBoundaryKey, extensionPoint
    }
  serviceBoundaryKey = attribute key { xsd:token }
}

##
##       Path -
##       Contains a list of via elements -
##       places through which information flowed
##
div {
  path =
    element path {
      element via { source, extensionPoint }+
    }
}

##
##       Expires pattern
##
div {
  expires =
    attribute expires { xsd:dateTime | "NO-CACHE" | "NO-EXPIRATION" }
}

##
##       A QName list
##
div {
  qnameList = list { xsd:QName* }
}

##
##       A location-to-service mapping.
##
div {
  mapping =
    element mapping {
      element displayName {
        xsd:string,
        attribute xml:lang { xsd:language }
      }*,
      service,
      (serviceBoundary | serviceBoundaryReference)?,
      element uri { xsd:anyURI }*,
      element serviceNumber {
        xsd:string { pattern = "[0-9*#]+" }
      }?,
      extensionPoint,
      expires,
      attribute lastUpdated { xsd:dateTime },
      source,
      attribute sourceId { xsd:token },
      message
    }
}

##
##       Location validation
##
div {
  locationValidation =
    element locationValidation {
      element valid { qnameList }?,
      element invalid { qnameList }?,
      element unchecked { qnameList }?,
      extensionPoint
    }
}

##
##       Errors and Warnings Container.
##
div {
  errorContainer
  exceptionContainer =
    (badRequest?
     & internalError?
     & serviceSubstitution?
     & defaultMappingReturned?
     & forbidden?
     & notFound?
     & loop?
     & serviceNotImplemented?
     & serverTimeout?
     & serverError?
     & locationInvalid?
     & locationProfileUnrecognized?),
    extensionPoint,
    source
  errors = element errors { errorContainer exceptionContainer }
  warnings = element warnings { errorContainer exceptionContainer }
}

##
##       Basic Errors Exceptions
##
div {

  ##
  ##         Error         Exception pattern.
  ##
  basicError
  basicException = message, extensionPoint
  badRequest = element badRequest { basicError basicException }
  internalError = element internalError { basicError basicException }
  serviceSubstitution = element serviceSubstitution { basicError basicException }
  defaultMappingReturned =
    element defaultMappingReturned { basicException }
  forbidden = element forbidden { basicError basicException }
  notFound = element notFound { basicError basicException }
  loop = element loop { basicError basicException }
  serviceNotImplemented =
    element serviceNotImplemented { basicError basicException }
  serverTimeout = element serverTimeout { basicError basicException }
  serverError = element serverError { basicError basicException }
  locationInvalid = element locationInvalid { basicException }
  locationValidationUnavailable =
    element locationValidationUnavailable { basicException }
  locationProfileUnrecognized =
    element locationProfileUnrecognized {
      attribute unsupportedProfiles { xsd:NMTOKENS },
      basicError
      basicException
    }
}

##
##       Redirect.
##
div {
  ##
  ##         Redirect pattern
  ##
  redirect =
    element redirect {
      attribute target { appUniqueString },
      source,
      message,
      extensionPoint
    }
}

##
##       Some common patterns.
##
div {
  message =
    (attribute message { xsd:string },
     attribute xml:lang { xsd:language })?
  service = element service { xsd:anyURI }?
  appUniqueString =
    xsd:string { pattern = "([a-zA-Z0-9\-]+\.)+[a-zA-Z0-9]+" }
  source = attribute source { appUniqueString }
  serviceList =
    element serviceList {
      list { xsd:anyURI* }
    }
}

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

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

  ##
  ##         A wildcard pattern for including any element
  ##         from any other namespace.
  ##
  anyElement =
    (element * { anyElement }
     | attribute * { text }
     | text)*
  ##
  ##         A point where future extensions
  ##         (elements from other namespaces)
  ##         can be added.
  ##
  extensionPoint = notLost*
}

                         Figure 20: 21: RelaxNG schema

15.

16.  Internationalization Considerations

   This mechanism

   The LoST protocol is largely mostly meant for passing protocol information from one
   subsystem to another; machine-to-machine
   communications; as such, most of its elements are tokens not meant
   for direct human consumption.  If these tokens are presented to the
   end user, some localization may need to occur.  The content of the
   <displayName> element and the 'message' attributes may be displayed
   to the end user, and they are thus a complex types designed for this
   purpose.

   LoST exchanges information using XML.  All XML processors are
   required to understand UTF-8 and UTF-16 encodings, and therefore all
   LoST clients and servers MUST understand UTF-8 and UTF-16 encoded
   XML.  Additionally, LoST servers and clients MUST NOT encode XML with
   encodings other than UTF-8 or UTF-16.

16.

17.  IANA Considerations

16.1.

17.1.  U-NAPTR Registrations

   This document registers the following U-NAPTR application service
   tag:

   Application Service Tag:  LoST

   Defining Publication:  The specification contained within this
      document.

   This document registers the following U-NAPTR application protocol
   tags:

   o

      Application Protocol Tag:  http

      Defining Publication:  RFC 2616 [3]

   o

      Application Protocol Tag:  https

      Defining Publication:  RFC 2818 [4]

16.2.

17.2.  Content-type registration for 'application/lost+xml'

   This specification requests the registration of a new MIME type
   according to the procedures of RFC 4288 [7] and guidelines in RFC
   3023 [5].

   MIME media type name:  application

   MIME subtype name:  lost+xml

   Mandatory parameters:  none

   Optional parameters:  charset

      Indicates the character encoding of enclosed XML.

   Encoding considerations:  Uses XML, which can employ 8-bit
      characters, depending on the character encoding used.  See RFC
      3023 [5], Section 3.2.

   Security considerations:  This content type is designed to carry LoST
      protocol payloads.

   Interoperability considerations:  None

   Published specification:  RFCXXXX [NOTE TO IANA/RFC-EDITOR: Please
      replace XXXX with the RFC number of this specification.] this
      document

   Applications which use this media type:  Emergency and Location-based
      Systems

   Additional information:

      Magic Number:  None

      File Extension:  .lostxml

      Macintosh file type code:  'TEXT'

   Personal and email address for further information:  Hannes
      Tschofenig, Hannes.Tschofenig@siemens.com Hannes.Tschofenig@nsn.com

   Intended usage:  LIMITED USE

   Author:

      This specification is a work item of the IETF ECRIT working group,
      with mailing list address <ecrit@ietf.org>.

   Change controller:

      The IESG <iesg@ietf.org>

16.3.

17.3.  LoST Relax NG Schema Registration

   URI:  urn:ietf:params:xml:ns:lost1

   Registrant Contact:  IETF ECRIT Working Group, Hannes Tschofenig
      (Hannes.Tschofenig@siemens.com).
      (Hannes.Tschofenig@nsn.com).

   Relax NG Schema:  The Relax NG schema to be registered is contained
      in Section 14. 15.  Its first line is

   default namespace = "urn:ietf:params:xml:ns:lost1"

      and its last line is

   }

16.4.

17.4.  LoST Namespace Registration

   URI:  urn:ietf:params:xml:ns:lost1

   Registrant Contact:  IETF ECRIT Working Group, Hannes Tschofenig
      (Hannes.Tschofenig@siemens.com).
      (Hannes.Tschofenig@nsn.com).

   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 Namespace</title>
   </head>
   <body>
     <h1>Namespace for LoST</h1>
     <h2>urn:ietf:params:xml:ns:lost1</h2>
   <p>See <a href="[URL of published RFC]">RFCXXXX
       [NOTE TO IANA/RFC-EDITOR:
        Please replace XXXX with the RFC number of this
       specification.]</a>.</p>
   </body>
   </html>
   END

16.5.

17.5.  LoST Location Profile Registry

   This document seeks to create a registry of location profile names
   for the LoST protocol.  Profile names are XML tokens.  This registry
   will operate in accordance with RFC 2434 [2], Standards Action.

   geodetic-2d:

      Defined in Section 11.2 12.2.

   civic:

      Defined in Section 11.3

17. 12.3.

18.  Security Considerations

   There are multiple several threats to the overall system of which service
   mapping forms a part.  An attacker that can obtain service contact
   URIs can use those URIs to attempt to disrupt those services.  An
   attacker that can prevent the lookup of contact URIs can impair the
   reachability of such services.  An attacker that can eavesdrop on the
   communication requesting this lookup can surmise the existence of an
   emergency and possibly its nature, and may be able to use this to
   launch a physical attack on the caller.

   To avoid that an attacker can modify the query or its result, the use
   of channel security, such as TLS, is RECOMMENDED.

   Generally, authentication and authorization is not required for
   mapping queries.  If it is, authentication mechanism of the
   underlying transport mechanism, such as HTTP basic and digest
   authentication, MAY be used.  (Basic authentication SHOULD only be
   used in combination with TLS.)

   A more detailed description of threats and security requirements are
   provided in [17].

18.

19.  Acknowledgments

   We would like to the thank the following working group members for
   the detailed review of previous LoST document versions:

   o  Martin Thomson (Review July 2006)

   o  Jonathan Rosenberg (Review July 2006)

   o  Leslie Daigle (Review September 2006)

   o  Shida Schubert (Review November 2006)

   o  Martin Thomson (Review December 2006)

   o  Barbara Stark (Review January 2007)

   o  Patrik Faeltstroem (Review January 2007

   o  Shida Schubert (Review January 2007 as a designated expert
      reviewer)

   o  Jonathan Rosenberg (Review February 2007)

   o  Tom Taylor (Review February 2007)

   o  Theresa Reese (Review February 2007)

   o  Shida Schubert (Review February 2007)

   o  James Winterbottom (Review July 2007)

   We would also like to thank the following working group members for
   their input to selected design aspects of the LoST protocol:

   o  Leslie Daigle and Martin Thomson (DNS-based LoST discovery
      procedure)

   o  John Schnizlein (authoritive LoST answers)

   o  Rohan Mahy (display names)

   o  James Polk (error handling)

   o  Ron Watro and Richard Barnes (expiry of cached data)

   o  Stephen Edge, Keith Drage, Tom Taylor, Martin Thomson and James
      Winterbottom (Indication of PSAP Confidence Level)
   o  Martin Thomson (service boundary references)

   o  Martin Thomson (service URN in LoST response message)

   o  Cullen Jennings (service boundaries)

   o  Clive D.W. Feather, Martin Thomson (Validation Functionality)

   o  Roger Marshall (PSAP Preference in LoST response)

   o  James Winterbottom, Marc Linsner, Keith Drage, Tom-PT Taylor,
      Martin Thomson, John Schnizlein, Shida Schubert, Clive D.W.
      Feather, Richard Stastny, John Hearty, Roger Marshall, Jean-
      Francois Mule, Pierre Desjardins (Location Profiles)

   o  Michael Hammer, Patrik Faeltstroem, Stastny Richard, Thomson,
      Martin, Roger Marshall, Tom-PT Taylor, Spencer Dawkins, Drage,
      Keith (List Services functionality)

   o  Thomson, Martin, Michael Hammer (Mapping of Services)

   o  Shida Schubert, James Winterbottom, Keith Drage (default service
      URN)

   o  Otmar Lendl (LoST aggregation)

   o  Tom Taylor (Terminology)

   Klaus Darilion and Marc Linsner provided miscellaneous input to the
   design of the protocol.  Finally, we would like to thank Brian Rosen
   who participated in almost every discussion thread.

19.  Open Issues

   Please find

   Early implementation efforts lead to good feedback by two open issues at: http://www.ietf-ecrit.org:8080/lost/ source
   implementation groups.  We would like to thank the implementers for
   their work and for helping us to improve the quality of the
   specification:

   o  Wonsang Song

   o  Jong-Yul Kim

   o  Anna Makarowska

   o  Krzysztof Rzecki

   o  Blaszczyk Piotr

20.  References

20.1.  Normative References

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

   [2]   Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
         Considerations Section in RFCs", BCP 26, RFC 2434,
         October 1998.

   [3]   Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
         Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol --
         HTTP/1.1", RFC 2616, June 1999.

   [4]   Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [5]   Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types",
         RFC 3023, January 2001.

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

   [7]   Freed, N. and J. Klensin, "Media Type Specifications and
         Registration Procedures", BCP 13, RFC 4288, December 2005.

   [8]   Hansen, T., Hardie, T., and L. Masinter, "Guidelines   Daigle, L., "Domain-Based Application Service Location Using
         URIs and
         Registration Procedures for New URI Schemes", BCP 115, the Dynamic Delegation Discovery Service (DDDS)",
         RFC 4395, February 2006. 4848, April 2007.

   [9]   Schulzrinne, H., "A Uniform Resource Name (URN) for Services",
         draft-ietf-ecrit-service-urn-05
         draft-ietf-ecrit-service-urn-06 (work in progress),
         August 2006. March 2007.

   [10]  Thomson, M. and J. Winterbottom, "Revised Civic Location Format
         for PIDF-LO", draft-ietf-geopriv-revised-civic-lo-05 (work in
         progress), February 2007.

   [11]  Daigle, L., "Domain-based Application Service Location Using
         URIs and the Dynamic  Delegation Discovery Service (DDDS)",
         draft-daigle-unaptr-02 (work in progress), February 2007.

   [12]  Cox, S., Daisey, P., Lake, R., Portele, C., and A. Whiteside,
         "Geographic information - Geography Markup Language (GML)", OGC
         Standard OpenGIS 03-105r1, April 2004.

   [13]

   [12]  Reed, C. and M. Thomson, "GML 3.1.1 PIDF-LO Shape Application
         Schema for use by the Internet Engineering Task Force (IETF)",
         Candidate OpenGIS Implementation Specification , December 2006.

20.2.  Informative References

   [13]  Tschofenig, H., "GEOPRIV PIDF-LO Usage Clarification,
         Considerations and Recommendations",
         draft-ietf-geopriv-pdif-lo-profile-08 (work in progress),
         July 2007.

   [14]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [15]  Saint-Andre, P., Ed., "Extensible Messaging and Presence
         Protocol (XMPP): Instant Messaging and Presence", RFC 3921,
         October 2004.

   [16]  Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
         December 2004.

   [17]  Taylor, T., "Security Threats and Requirements for Emergency
         Call Marking and Mapping", draft-ietf-ecrit-security-threats-03 draft-ietf-ecrit-security-threats-04
         (work in progress), July 2006. April 2007.

   [18]  Schulzrinne, H. and R. Marshall, "Requirements for Emergency
         Context Resolution with Internet Technologies",
         draft-ietf-ecrit-requirements-12
         draft-ietf-ecrit-requirements-13 (work in progress),
         August 2006.
         March 2007.

   [19]  Schulzrinne, H., "Location-to-URL Mapping Architecture and
         Framework", draft-ietf-ecrit-mapping-arch-01 draft-ietf-ecrit-mapping-arch-02 (work in
         progress), December 2006. July 2007.

   [20]  Rosen, B. and J. Polk, "Best Current Practice for
         Communications Services in support of Emergency  Calling",
         draft-ietf-ecrit-phonebcp-00
         draft-ietf-ecrit-phonebcp-01 (work in progress), October 2006. March 2007.

Appendix A.  Non-Normative RELAX NG Schema in XML Syntax

   <?xml version="1.0" encoding="UTF-8"?>
   <grammar ns="urn:ietf:params:xml:ns:lost1"
           xmlns="http://relaxng.org/ns/structure/1.0"
           xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
           datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">

           <start>
       <a:documentation>
         Location-to-Service Translation Protocol (LoST)

         A LoST XML instance has three request types, each with
         a cooresponding response type: find service, list services,
         and get service boundary.
       </a:documentation>
       <choice>
         <ref name="findService" />
         <ref name="listServices" />
         <ref name="listServicesByLocation" />
         <ref name="getServiceBoundary" />
         <ref name="findServiceResponse" />
         <ref name="listServicesResponse" />
         <ref name="listServicesByLocationResponse" />
         <ref name="getServiceBoundaryResponse" />
         <ref name="errors" />
         <ref name="redirect" />
       </choice>
           </start>

     <div>
       <a:documentation>
         The queries.
       </a:documentation>

       <define name="findService">
         <element name="findService">
           <oneOrMore>
             <element name="location">
               <ref name="locationInformation" />
             </element>
           </oneOrMore>
           <ref name="commonRequestPattern" />
           <optional>
             <attribute name="validateLocation">
               <data type="boolean" />
               <a:defaultValue>false</a:defaultValue>
             </attribute>
           </optional>
           <optional>
             <attribute name="serviceBoundary">
               <choice>
                 <value>reference</value>
                 <value>value</value>
               </choice>
               <a:defaultValue>reference</a:defaultValue>
             </attribute>
           </optional>
           <optional>
             <attribute name="recursive">
               <data type="boolean" />
                 <a:defaultValue>false</a:defaultValue>
             </attribute>
           </optional>
         </element>
       </define>

       <define name="listServices">
         <element name="listServices">
           <ref name="commonRequestPattern" />
         </element>
       </define>

       <define name="listServicesByLocation">
         <element name="listServicesByLocation">
           <zeroOrMore>
             <element name="location">
               <ref name="locationInformation" />
             </element>
           </zeroOrMore>
           <ref name="commonRequestPattern" />
           <optional>
             <attribute name="recursive">
               <data type="boolean" />
               <a:defaultValue>true</a:defaultValue>
             </attribute>
           </optional>
         </element>
       </define>

       <define name="getServiceBoundary">
         <element name="getServiceBoundary">
           <ref name="serviceBoundaryKey" />
           <ref name="extensionPoint" />
         </element>
       </define>

     </div>

     <div>
       <a:documentation>
         The responses.
       </a:documentation>

       <define name="findServiceResponse">
         <element name="findServiceResponse">
           <oneOrMore>
             <ref name="mapping" />
           </oneOrMore>
           <optional>
             <ref name="locationValidation" />
           </optional>
           <ref name="commonResponsePattern" />
         </element>
       </define>

       <define name="listServicesResponse">
         <element name="listServicesResponse">
           <ref name="serviceList" />
           <ref name="commonResponsePattern" />
         </element>
       </define>

       <define name="listServicesByLocationResponse">
         <element name="listServicesByLocationResponse">
           <ref name="serviceList" />
           <ref name="commonResponsePattern" />
         </element>
       </define>

       <define name="getServiceBoundaryResponse">
         <element name="getServiceBoundaryResponse">
           <ref name="serviceBoundary"/>
           <ref name="commonResponsePattern" />
         </element>
       </define>

     </div>

     <div>
       <a:documentation>
         A pattern common to some of the queries.
       </a:documentation>

       <define name="commonRequestPattern">
         <ref name="service" />
         <optional>
           <ref name="path" />
         </optional>
         <ref name="extensionPoint" />
       </define>
     </div>

     <div>
       <a:documentation>
         A pattern common to responses.
       </a:documentation>

       <define name="commonResponsePattern">
         <zeroOrMore>
           <ref name="warnings" />
         </zeroOrMore>
         <ref name="path" />
         <ref name="extensionPoint" />
       </define>
     </div>

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

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

     <div>
       <a:documentation>
         Service Boundary
       </a:documentation>
       <define name="serviceBoundary">
         <oneOrMore>
           <element name="serviceBoundary">
             <ref name="locationInformation" />
           </element>
         </oneOrMore>
       </define>
     </div>

     <div>
       <a:documentation>
         Service Boundary Reference
       </a:documentation>

       <define name="serviceBoundaryReference">

         <element name="serviceBoundaryReference">
           <ref name="source" />
           <ref name="serviceBoundaryKey" />
           <ref name="extensionPoint" />
         </element>
       </define>

       <define name="serviceBoundaryKey">
         <attribute name="key">
           <data type="token" />
         </attribute>
       </define>

     </div>

     <div>
       <a:documentation>
         Path -
         Contains a list of via elements -
         places through which information flowed
       </a:documentation>

       <define name="path">
         <element name="path">
           <oneOrMore>
             <element name="via">
               <ref name="source" />
               <ref name="extensionPoint" />
             </element>
           </oneOrMore>
         </element>
       </define>
     </div>

     <div>
       <a:documentation>
         Expires pattern
       </a:documentation>

       <define name="expires">
         <attribute name="expires">
           <choice>
             <data type="dateTime"/>
             <value>NO-CACHE</value>
             <value>NO-EXPIRATION</value>
           </choice>
         </attribute>
       </define>
     </div>

     <div>
       <a:documentation>
         A QName list
       </a:documentation>

       <define name="qnameList">
         <list>
           <zeroOrMore>
             <data type="QName"/>
           </zeroOrMore>
         </list>
       </define>
     </div>

     <div>
       <a:documentation>
         A location-to-service mapping.
       </a:documentation>

       <define name="mapping">
         <element name="mapping">
           <zeroOrMore>
             <element name="displayName">
               <data type="string"/>
               <attribute name="xml:lang">
                 <data type="language"/>
               </attribute>
             </element>
           </zeroOrMore>
           <ref name="service" />
           <optional>
             <choice>
               <ref name="serviceBoundary"/>
               <ref name="serviceBoundaryReference"/>
             </choice>
           </optional>
           <zeroOrMore>
             <element name="uri">
               <data type="anyURI"/>
             </element>
           </zeroOrMore>
           <optional>
             <element name="serviceNumber">
               <data type="string">
                 <param name="pattern">[0-9*#]+</param>
               </data>
             </element>
           </optional>
           <ref name="extensionPoint"/>
           <ref name="expires"/>
           <attribute name="lastUpdated">
             <data type="dateTime"/>
           </attribute>
           <ref name="source" />
           <attribute name="sourceId">
             <data type="token" />
           </attribute>
           <ref name="message"/>
         </element>
       </define>

     </div>

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

       <define name="locationValidation">
         <element name="locationValidation">
           <optional>
             <element name="valid">
               <ref name="qnameList" />
             </element>
           </optional>
           <optional>
             <element name="invalid">
               <ref name="qnameList" />
             </element>
           </optional>
           <optional>
             <element name="unchecked">
               <ref name="qnameList" />
             </element>
           </optional>
           <ref name="extensionPoint"/>
         </element>
       </define>
     </div>

     <div>
       <a:documentation>
         Errors and Warnings Container.
       </a:documentation>

       <define name="errorContainer"> name="exceptionContainer">
         <interleave>
           <optional>
             <ref name="badRequest" />
           </optional>
           <optional>
             <ref name="internalError" />
           </optional>
           <optional>
             <ref name="serviceSubstitution" />
           </optional>
           <optional>
             <ref name="forbidden" />
           </optional>
           <optional>
             <ref name="notFound" />
           </optional>
           <optional>
             <ref name="loop" />
           </optional>
           <optional>
             <ref name="serviceNotImplemented" />
           </optional>
           <optional>
             <ref name="serverTimeout" />
           </optional>
           <optional>
             <ref name="serverError" />
           </optional>
           <optional>
             <ref name="locationInvalid" />
           </optional>
           <optional>
             <ref name="locationProfileUnrecognized" />
           </optional>
         </interleave>
         <ref name="extensionPoint" />
         <ref name="source" />
       </define>

       <define name="errors">
         <element name="errors">
           <ref name="errorContainer" name="exceptionContainer" />
         </element>
       </define>

       <define name="warnings">
         <element name="warnings">
           <ref name="errorContainer" name="exceptionContainer" />
         </element>
       </define>

     </div>

     <div>
       <a:documentation>
         Basic Errors Exceptions
       </a:documentation>

       <define name="basicError"> name="basicException">
         <a:documentation>
           Error
           Exception pattern.
         </a:documentation>
         <ref name="message"/>
         <ref name="extensionPoint" />
       </define>

       <define name="badRequest">
         <element name="badRequest">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

       <define name="internalError">
         <element name="internalError">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>
       <define name="serviceSubstitution">
         <element name="serviceSubstitution">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

       <define name="forbidden">
         <element name="forbidden">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

       <define name="notFound">
         <element name="notFound">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

       <define name="loop">
         <element name="loop">
           <ref name="basicError" name="basicException" />
         </element>
       </define>

       <define name="serviceNotImplemented">
         <element name="serviceNotImplemented">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

       <define name="serverTimeout">
         <element name="serverTimeout">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

       <define name="serverError">
         <element name="serverError">
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

       <define name="locationInvalid">
         <element name="locationInvalid">
           <ref name="basicException"/>
         </element>
       </define>
       <define name="locationValidationUnavailable">
         <element name="locationValidationUnavailable">
           <ref name="basicException" />
         </element>
       </define>

       <define name="locationProfileUnrecognized">
         <element name="locationProfileUnrecognized">
           <attribute name="unsupportedProfiles">
             <data type="NMTOKENS" />
           </attribute>
           <ref name="basicError"/> name="basicException"/>
         </element>
       </define>

     </div>

     <div>
       <a:documentation>
         Redirect.
       </a:documentation>

       <define name="redirect">
         <a:documentation>
           Redirect pattern
         </a:documentation>
         <element name="redirect">
           <attribute name="target">
             <ref name="appUniqueString" />
           </attribute>
           <ref name="source" />
           <ref name="message" />
           <ref name="extensionPoint" />
         </element>
       </define>

     </div>

     <div>
       <a:documentation>
         Some common patterns.
       </a:documentation>

       <define name="message">
         <optional>
           <group>
             <attribute name="message">
               <data type="string"/>
             </attribute>
             <attribute name="xml:lang">
               <data type="language"/>
             </attribute>
           </group>
         </optional>
       </define>

       <define name="service">
         <optional>
           <element name="service">
             <data type="anyURI"/>
           </element>
         </optional>
       </define>

       <define name="appUniqueString">
         <data type="string">
           <param name="pattern">([a-zA-Z0-9\-]+\.)+[a-zA-Z0-9]+</param>
         </data>
       </define>

       <define name="source">
         <attribute name="source">
           <ref name="appUniqueString" />
         </attribute>
       </define>

       <define name="serviceList" >
         <element name="serviceList">
           <list>
             <zeroOrMore>
               <data type="anyURI" />
             </zeroOrMore>
           </list>
         </element>
       </define>

     </div>

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

       <define name="notLost">
         <a:documentation>
           Any element not in the LoST namespace.
         </a:documentation>
         <element>
           <anyName>
             <except>
               <nsName ns="urn:ietf:params:xml:ns:lost1"/>
               <nsName/>
             </except>
           </anyName>
           <ref name="anyElement"/>
         </element>
       </define>

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

     </div>

   </grammar>
                                 Figure 24 25

Authors' Addresses

   Ted Hardie
   Qualcomm, Inc.

   Email: hardie@qualcomm.com

   Andrew Newton
   SunRocket
   8045 Leesburg Pike,
   TranTech, Inc.
   4900 Seminary Road, Suite 300
   Vienna, 215
   Alexandria, VA  22182  22311
   US

   Phone: +1 703 636 0852 671 9873
   Email: andy@hxr.us

   Henning Schulzrinne
   Columbia University
   Department of Computer Science
   450 Computer Science Building
   New York, NY  10027
   US

   Phone: +1 212 939 7004
   Email: hgs+ecrit@cs.columbia.edu
   URI:   http://www.cs.columbia.edu

   Hannes Tschofenig
   Nokia Siemens Networks GmbH & Co KG
   Otto-Hahn-Ring 6
   Munich, Bavaria  81739
   Germany

   Phone: +49 89 636 40390
   Email: Hannes.Tschofenig@siemens.com Hannes.Tschofenig@nsn.com
   URI:   http://www.tschofenig.com

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