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Versions: (draft-hardie-ecrit-lost) 00 01 02 03 04 05 06 07 08 09 10 RFC 5222

ECRIT                                                          T. Hardie
Internet-Draft                                            Qualcomm, Inc.
Intended status: Standards Track                               A. Newton
Expires: August 15, 2007                                       SunRocket
                                                          H. Schulzrinne
                                                             Columbia U.
                                                           H. Tschofenig
                                           Siemens Networks GmbH & Co KG
                                                       February 11, 2007


            LoST: A Location-to-Service Translation Protocol
                      draft-ietf-ecrit-lost-04.txt

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   This Internet-Draft will expire on August 15, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).









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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 and Their Resolution  . . . . . . . . . . . . . .  8
   5.  The <mapping> Element  . . . . . . . . . . . . . . . . . . . .  9
     5.1.  Data source and version: The 'source', 'sourceId' and
           'version' Attributes . . . . . . . . . . . . . . . . . . .  9
     5.2.  Time of Last Update: The 'lastUpdated' Attribute . . . . .  9
     5.3.  Validity: The 'expires' Attribute  . . . . . . . . . . . .  9
     5.4.  Describing the Service with the <displayName> Element  . . 10
     5.5.  The Mapped Service:  the <service> Element . . . . . . . . 10
     5.6.  Defining the Service Region with the <serviceBoundary>
           Element  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.7.  Service Boundaries by Reference: the
           <serviceBoundaryReference> Element . . . . . . . . . . . . 11
     5.8.  The Service Number Element . . . . . . . . . . . . . . . . 11
     5.9.  Service URLs: the <uri> Element  . . . . . . . . . . . . . 12
   6.  Path of Request:  <path> Element . . . . . . . . . . . . . . . 13
   7.  Mapping a Location and Service to URLs: <findService>  . . . . 14
     7.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 14
     7.2.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . 14
       7.2.1.  Example Using Geodetic Coordinates . . . . . . . . . . 14
       7.2.2.  Civic Address Mapping Example  . . . . . . . . . . . . 15
     7.3.  Components of the <findService> Request  . . . . . . . . . 17
       7.3.1.  The <location> Element . . . . . . . . . . . . . . . . 17
       7.3.2.  Identifying the Service:  The <service> Element  . . . 18
       7.3.3.  Recursion  . . . . . . . . . . . . . . . . . . . . . . 18
       7.3.4.  Service Boundary . . . . . . . . . . . . . . . . . . . 18
       7.3.5.  Requesting Civic Location Validation . . . . . . . . . 18
     7.4.  Components of the Mapping Response
           <findServiceResponse>  . . . . . . . . . . . . . . . . . . 20
       7.4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . 20
       7.4.2.  Civic Address Validation:  the
               <locationValidation> Element . . . . . . . . . . . . . 21
   8.  Retrieving the Service Boundary via <getServiceBoundary> . . . 22
   9.  List Services: <listServices>  . . . . . . . . . . . . . . . . 25
   10. List Services By Location: <listServicesByLocation>  . . . . . 26
   11. Location Profiles  . . . . . . . . . . . . . . . . . . . . . . 28



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     11.1. Location Profile Usage . . . . . . . . . . . . . . . . . . 29
     11.2. Two Dimensional Geodetic Profile . . . . . . . . . . . . . 32
     11.3. Basic Civic Profile  . . . . . . . . . . . . . . . . . . . 33
   12. Errors, Warnings, and Redirects  . . . . . . . . . . . . . . . 34
     12.1. Errors . . . . . . . . . . . . . . . . . . . . . . . . . . 34
     12.2. Warnings . . . . . . . . . . . . . . . . . . . . . . . . . 35
     12.3. Redirects  . . . . . . . . . . . . . . . . . . . . . . . . 36
   13. LoST Transport . . . . . . . . . . . . . . . . . . . . . . . . 37
   14. Relax NG Schema  . . . . . . . . . . . . . . . . . . . . . . . 38
   15. Internationalization Considerations  . . . . . . . . . . . . . 45
   16. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 46
     16.1. U-NAPTR Registrations  . . . . . . . . . . . . . . . . . . 46
     16.2. Content-type registration for 'application/lost+xml' . . . 46
     16.3. LoST Relax NG Schema Registration  . . . . . . . . . . . . 48
     16.4. LoST Namespace Registration  . . . . . . . . . . . . . . . 48
     16.5. LoST Location Profile Registry . . . . . . . . . . . . . . 49
   17. Security Considerations  . . . . . . . . . . . . . . . . . . . 50
   18. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 51
   19. Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 53
   20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
     20.1. Normative References . . . . . . . . . . . . . . . . . . . 54
     20.2. Informative References . . . . . . . . . . . . . . . . . . 55
   Appendix A.  Non-Normative RELAX NG Schema in XML Syntax . . . . . 56
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 70
   Intellectual Property and Copyright Statements . . . . . . . . . . 71


























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1.  Introduction

   This document describes a protocol for mapping a service identifier
   [10] and location information compatible with PIDF-LO [7], namely
   revised civic location information [11] and GML [13]) to one or more
   service URL.  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 service URN.  For example, in the United States,
   the "2-1-1" and "3-1-1" service numbers follow a similar 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 Section 3.5 of [18]
   for a description of validation).  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
   caches 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.  Later
   documents may describe how LoST messages could be carried over other
   transports.

   This document focuses on the description of the protocol between the
   mapping client and the mapping server.  The relationship between
   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 [10]) 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



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   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, the protocol also
   allows to retrieve the service boundary (see Section 8) and to list
   the services available for a particular location (see Section 10) or
   supported by a particular server (see Section 9).













































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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 furthermore uses the terminology defined in [18].












































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3.  Overview of Protocol Usage

   The client may perform the mapping at any time.  Among the common
   triggers for mapping requests are:

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

   2.  When the client detects that its location has changed
       sufficiently that it is outside the bounds of the service region
       returned in an earlier LoST query.

   3.  When cached mapping information has expired.

   4.  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 5.3), or they become invalid if the caller's device moves
   beyond the boundaries of the service region.




























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4.  LoST servers and Their Resolution

   A LoST server may be discovered using a U-NAPTR/DDDS [12] application
   unique string (AUS), in the form of a DNS name.

   An example is 'lostserver.example.com'

   Clients need to use the U-NAPTR [12] 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 the AUS
   "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 AUS by means beyond the scope of this
   specification, such as SIP configuration and DHCP.






















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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.  Data source and version: The 'source', 'sourceId' and 'version'
      Attributes

   The 'source', 'sourceId' and 'version' attributes uniquely identify a
   particular mapping record.  They are created by the authoritative
   source for a mapping and 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 higher version number.

   The 'source' attribute contains a LoST application unique string
   identifying the authoritative generator of the mapping.  See
   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 'version' attribute is a positive integer that is incremented for
   each change in the mapping.  The XML data type does not specify an
   upper bound for this attribute and thus, the value MUST NOT wrap
   around.  Thus, a higher version number refers to a more recent
   mapping.  A mapping maintains its sourceId value as long as it
   remains logically the same, e.g., represents the same service
   boundary or replaces an earlier service boundary.

5.2.  Time of Last Update: The 'lastUpdated' Attribute

   The 'lastUpdated' attribute describes when the mapping 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.  The attribute is
   REQUIRED.

5.3.  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.



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   The 'expires' attribute is REQUIRED to be included in the <mapping>
   element.

   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.

5.4.  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.

5.5.  The Mapped Service:  the <service> Element

   The <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 [10] in
       the <service> element of the request, exists for the location
       indicated, then the LoST server puts the service URN from the
       request into the <service> element.

   2.  If, however, the requested service, identified by the service URN
       [10] in the <service> element in the request, does not exist for
       the location indicated, the server can either return an
       <serviceNotImplemented> (Section 12.1) 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.

5.6.  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 5.7).  If a client moves outside the service
   area and wishes to obtain current service data, it sends a new query



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   with its current location.  The service region is described by value
   in one or more <serviceBoundary> elements, each formatted according
   to a different location profile, identified by the 'profile' atribute
   (see Section 11).  The response MUST contain at least one service
   boundary using 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 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.

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

   Since geodetic service boundaries may contain thousands of points and
   thus be quite large, clients may opt to conserve bandwidth and
   request a reference to the service boundary instead of the value
   described in Section 5.6.  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) request.

   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.

5.8.  The Service Number 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



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   service.

5.9.  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'.









































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6.  Path of Request:  <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 first
   received the request from the client.  The authoritative server
   copies the <path> element verbatim into the response.

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

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

































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

7.1.  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.  Examples

7.2.1.  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 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, instructing the client
   that it may contact them via the URIs "sip:sfpd@example.com" and
   "xmpp:sfpd@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.




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   <?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">
       <displayName xml:lang="en">
         San Francisco 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:sfpd@example.com</uri>
       <uri>xmpp:sfpd@example.com</uri>
       <serviceNumber>911</serviceNumber>
     </mapping>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
     </path>
   </findServiceResponse>

             Figure 3: A <findServiceResponse> geodetic answer

7.2.2.  Civic Address Mapping Example

   The following is an example of mapping a service to a location much
   like the example in Section 7.2.1, 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).






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   <?xml version="1.0" encoding="UTF-8"?>
   <findService xmlns="urn:ietf:params:xml:ns:lost1"
     recursive="true" serviceBoundary="value">
     <location
       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.



















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   <?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" >
       <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>
   </findServiceResponse>

          Figure 5: A <findServiceResponse> civic address answer

7.3.  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 must be contained in the
   response.

7.3.1.  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).  There MUST NOT be more than one location element
   for each distinct location profile.  The order of location objects is
   significant; the server uses the first location object where it
   understands the location profile.



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7.3.2.  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 [10].

7.3.3.  Recursion

   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".

   In recursive mode, the LoST server initiates queries on behalf of the
   requester and returns the result to the requester, inserting a <via>
   element to track the response chain.  The <via> elements are appended
   in responses in order of visit, i.e., the first <via> element
   contains the authoritative server and <via> elements below indicate
   servers that the response traversed on its way back to the original
   querier.

7.3.4.  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.  Servers SHOULD NOT
   return a by-value service boundaries if the querier requested a
   reference.

7.3.5.  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.  The example in Figure 6 demonstrates address
   validation, omitting the standard response elements.








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   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     recursive="true"
     validateLocation="true"
     serviceBoundary="value">
     <location 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






























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   <?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" >
       <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>
     </locationValidation>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
     </path>
   </findServiceResponse>

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

7.4.  Components of the Mapping Response <findServiceResponse>

7.4.1.  Overview

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





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7.4.2.  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 MUST include this
   information if the 'validateLocation' attribute in the request was
   true.  Each element contains a list of tokens separated by white
   space, enumerating the civic location lables 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.

   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) 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.
























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8.  Retrieving the Service Boundary via <getServiceBoundary>

   As discussed in Section 5.6, 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.
   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 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



















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   <?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">
       <displayName xml:lang="en">
         San Francisco Police Department
       </displayName>
       <service>urn:service:sos.police</service>
       <serviceBoundaryReference
         source="authoritative.example"
         key="7214148E0433AFE2FA2D48003D31172E" />
       <uri>sip:sfpd@example.com</uri>
       <uri>xmpp:sfpd@example.com</uri>
       <serviceNumber>911</serviceNumber>
     </mapping>
     <path>
       <via source="authoritative.example"/>
       <via source="resolver.example"/>
     </path>
   </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.











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   <?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"/>
     </path>
   </getServiceBoundaryResponse>

            Figure 11: Civic Address Service Boundary Response
































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9.  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 (Section 10) 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>







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10.  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), 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> elements track the progress of the
   request.  By its nature, the query can only indicate the services
   that a particular server can determine, not all possible services
   that might be offered.  Unlike <ListServices>, the answer describes
   the services available at a specific location, not just those
   understood by the server.

   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 profile="geodetic-2d">
       <p2:Point id="point1" srsName="epsg:4326">
         <p2:coordinates>37:46:30N 122:25:10W</p2:coordinates>
       </p2:Point>
     </location>
     <service>urn:service:sos</service>
   </listServicesByLocation>

           Figure 14: Example of <ListServicesbyLocation> query







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   <?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"/>
    </path>
   </listServicesByLocationResponse>

               Figure 15: Example of <ListServices> response





























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11.  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
   possible to standardize other profiles in the future.  The two
   baseline profiles are:

   geodetic-2d:

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


   civic:

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

   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.




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11.1.  Location Profile Usage

   A location profile is identified by a token in an IANA-maintained
   registry (Section 16.5).  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 'profile' attribute that
   indicates the location format of the child elements.  The concept of
   location profiles are described in Section 11.  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 to the location profile
   specified in the 'profile' attribute.  When multiple <location>
   elements are included then it enables the server to send location
   information compliant with multiple location profiles.

   Using the location profiles defined in this document, the following
   rules insure basic interoperatiblity 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, 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.  There can only be one instance of each location profile in a
       query.

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

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

   6.  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).




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   7.  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 location profile.  Client X sends location
   information to Server Y, which does not understand the
   uber-complex-3D 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.




































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   <?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="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>
     </location>
     <location 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 16: Example of a <findServices> query with baseline profile
                             interoperability
















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   <?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">
       <displayName xml:lang="en">
         San Francisco 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"/>
     </path>
   </findServiceResponse>

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

11.2.  Two Dimensional Geodetic Profile

   The geodetic-2d location profile is identified by geodetic-2d.
   Clients use this profile by placing a GML [13] <position> element
   within the <location> element.  This is defined by the 'point2D'
   pattern in the LoST schema (see Section 14).

   Servers use this profile by placing a GML [13] <Polygon> element
   within the <serviceBoundary> element.  This is defined by the
   'polygon' pattern in the LoST schema (see Section 14).



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11.3.  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 [11], within the <location> element.

   Servers use this profile by placing a <civicAddress> element, defined
   in [11], within the <serviceBoundary> element.











































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12.  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.  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.  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 the server
      (see Section 11).



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   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.  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.




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   This version of the specification does not define any warning
   elements.

12.3.  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: Example of a redirect resonse

























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13.  LoST Transport

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





































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14.  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.



default namespace = "http://www.opengis.net/gml"
namespace a = "http://relaxng.org/ns/compatibility/annotations/1.0"
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 ns1:findService {
      element ns1:location { locationInformation }+,
      commonRequestPattern,
      attribute validateLocation {
        xsd:boolean >> a:defaultValue [ "false" ]
      }?,
      attribute serviceBoundary {
        ("reference" | "value") >> a:defaultValue [ "reference" ]
      }?,
      attribute recursive { xsd:boolean >> a:defaultValue [ "true" ] }?
    }
  listServices = element ns1:listServices { commonRequestPattern }



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  listServicesByLocation =
    element ns1:listServicesByLocation {
      element ns1:location { locationInformation }*,
      commonRequestPattern,
      attribute recursive { xsd:boolean >> a:defaultValue [ "true" ] }?
    }
  getServiceBoundary =
    element ns1:getServiceBoundary {
      serviceBoundaryKey, extensionPoint
    }
}

##
##       The responses.
##
div {
  findServiceResponse =
    element ns1:findServiceResponse {
      mapping+, locationValidation?, commonResponsePattern
    }
  listServicesResponse =
    element ns1:listServicesResponse {
      serviceList, commonResponsePattern
    }
  listServicesByLocationResponse =
    element ns1:listServicesByLocationResponse {
      serviceList, commonResponsePattern
    }
  getServiceBoundaryResponse =
    element ns1:getServiceBoundaryResponse {
      serviceBoundary, commonResponsePattern
    }
}

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

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




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

##
##       Service Boundary
##
div {
  serviceBoundary = element ns1:serviceBoundary { locationInformation }+
}

##
##       Service Boundary Reference
##
div {
  serviceBoundaryReference =
    element ns1:serviceBoundaryReference {
      source, serviceBoundaryKey, extensionPoint
    }
  serviceBoundaryKey = attribute key { xsd:token }
}

##
##       Path -
##       Contains a list of via elements -
##       places through which information flowed
##
div {
  path =
    element ns1:path {
      element ns1:via { source, extensionPoint }*
    }
}

##
##       Expires pattern
##
div {
  expires = attribute expires { xsd:dateTime }
}

##
##       A QName list



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

##
##       A location-to-service mapping.
##
div {
  mapping =
    element ns1:mapping {
      element ns1:displayName {
        xsd:string,
        attribute xml:lang { xsd:language }
      }*,
      service,
      (serviceBoundary | serviceBoundaryReference)?,
      element ns1:uri { xsd:anyURI }*,
      element ns1:serviceNumber {
        xsd:string { pattern = "[0-9*#]+" }
      }?,
      extensionPoint,
      expires,
      attribute lastUpdated { xsd:dateTime },
      source,
      attribute sourceId { xsd:token },
      attribute version { xsd:positiveInteger },
      message
    }
}

##
##       Location validation
##
div {
  locationValidation =
    element ns1:locationValidation {
      element ns1:valid { qnameList }?,
      element ns1:invalid { qnameList }?,
      element ns1:unchecked { qnameList }?,
      extensionPoint
    }
}

##
##       Errors and Warnings Container.
##
div {



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  errorContainer =
    (badRequest?
     & internalError?
     & serviceSubstitution?
     & forbidden?
     & notFound?
     & loop?
     & serviceNotImplemented?
     & serverTimeout?
     & serverError?
     & locationProfileUnrecognized?),
    extensionPoint,
    source
  errors = element ns1:errors { errorContainer }
  warnings = element ns1:warnings { errorContainer }
}

##
##       Basic Errors
##
div {

  ##
  ##         Error pattern.
  ##
  basicError = message, extensionPoint
  badRequest = element ns1:badRequest { basicError }
  internalError = element ns1:internalError { basicError }
  serviceSubstitution = element ns1:serviceSubstitution { basicError }
  forbidden = element ns1:forbidden { basicError }
  notFound = element ns1:notFound { basicError }
  loop = element ns1:loop { basicError }
  serviceNotImplemented =
    element ns1:serviceNotImplemented { basicError }
  serverTimeout = element ns1:serverTimeout { basicError }
  serverError = element ns1:serverError { basicError }
  locationProfileUnrecognized =
    element ns1:locationProfileUnrecognized {
      attribute unsupportedProfiles { xsd:NMTOKENS },
      basicError
    }
}

##
##       Redirect.
##
div {




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  ##
  ##         Redirect pattern
  ##
  redirect =
    element ns1:redirect {
      attribute target { appUniqueString },
      source,
      message,
      extensionPoint
    }
}

##
##       Some common patterns.
##
div {
  message =
    (attribute message { xsd:string },
     attribute xml:lang { xsd:language })?
  service = element ns1:service { xsd:anyURI }?
  appUniqueString =
    xsd:string { pattern = "([a-zA-Z0-9\-]+\.)+[a-zA-Z0-9]+" }
  source = attribute source { appUniqueString }
  serviceList =
    element ns1: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)*



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

  ##
  ##         A 2D point from GML.
  ##
  point2d =
    element Point {
      attribute srsName { "urn:ogc:def:crs:EPSG::4326" },
      pos
    }

  ##
  ##         A GML position
  ##
  pos =
    element pos {
      list { xsd:double }
    }

  ##
  ##         A Linear Ring from GML.
  ##
  linearRing = element LinearRing { pos, pos, pos, pos+ }

  ##
  ##         A Polygon from GML.
  ##
  polygon =
    element Polygon {
      attribute srsName { "urn:ogc:def:crs:EPSG::4326" },
      element exterior { linearRing },
      element interior { linearRing }*
    }
}

                         Figure 20: RelaxNG schema










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15.  Internationalization Considerations

   This mechanism is largely for passing protocol information from one
   subsystem to another; 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.




































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16.  IANA Considerations

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

   This specification requests the registration of a new MIME type
   according to the procedures of RFC 4288 [8] 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.






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   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


   Intended usage:  LIMITED USE


   Author:

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





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   Change controller:

      The IESG <iesg@ietf.org> delegated to the IETF ECRIT working
      group, if it is still active.

16.3.  LoST Relax NG Schema Registration

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

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

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

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

      and its last line is

   }

16.4.  LoST Namespace Registration

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

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

   XML:






















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   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.  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


   civic:

      Defined in Section 11.3
















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17.  Security Considerations

   There are multiple 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].





























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18.  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)

   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)





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   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)

   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.






























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19.  Open Issues

   Please find open issues at: http://www.ietf-ecrit.org:8080/lost/
















































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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]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
         Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
         January 2005.

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

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

   [9]   Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
         Registration Procedures for New URI Schemes", BCP 115,
         RFC 4395, February 2006.

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

   [11]  Thomson, M. and J. Winterbottom, "Revised Civic Location Format
         for PIDF-LO", draft-ietf-geopriv-revised-civic-lo-04 (work in
         progress), September 2006.

   [12]  Daigle, L., "Domain-based Application Service Location Using
         URIs and the Dynamic  Delegation Discovery Service (DDDS)",
         draft-daigle-unaptr-01 (work in progress), October 2006.

   [13]  OpenGIS, "Open Geography Markup Language (GML) Implementation
         Specification", OGC OGC 02-023r4, January 2003.



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20.2.  Informative References

   [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
         (work in progress), July 2006.

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

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

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






















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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>



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             </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>true</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>



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       </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>



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

       <define name="commonRequestPattern">
         <ref name="service" />
         <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>
         <attribute name="profile">
           <data type="NMTOKEN" />
         </attribute>
       </define>
     </div>

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

       <define name="serviceBoundary">
         <oneOrMore>
           <element name="serviceBoundary">
             <ref name="locationInformation" />



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

     <div>
       <a:documentation>



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         Expires pattern
       </a:documentation>

       <define name="expires">
         <attribute name="expires">
           <data type="dateTime"/>
         </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">



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               <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>
           <attribute name="version">
             <data type="positiveInteger" />
           </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" />



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             </element>
           </optional>
           <ref name="extensionPoint"/>
         </element>
       </define>
     </div>

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

       <define name="errorContainer">
         <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="locationProfileUnrecognized" />
           </optional>
         </interleave>
         <ref name="extensionPoint" />
         <ref name="source" />
       </define>



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

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

     </div>

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

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

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

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

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

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



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         </element>
       </define>

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

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

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

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

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

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

     </div>

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



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       <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>




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       <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>



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               <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>

       <define name="point2d">
         <a:documentation>
           A 2D point from GML.
         </a:documentation>
         <element name="Point" ns="http://www.opengis.net/gml">
           <attribute name="srsName">
             <value>urn:ogc:def:crs:EPSG::4326</value>
           </attribute>
           <ref name="pos"/>
         </element>
       </define>

       <define name="pos">
         <a:documentation>
           A GML position
         </a:documentation>
         <element name="pos" ns="http://www.opengis.net/gml">
           <list>
             <data type="double"/>
           </list>
         </element>
       </define>

       <define name="linearRing">
         <a:documentation>
           A Linear Ring from GML.



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         </a:documentation>
         <element name="LinearRing"
           ns="http://www.opengis.net/gml">
           <ref name="pos"/>
           <ref name="pos"/>
           <ref name="pos"/>
           <oneOrMore>
             <ref name="pos"/>
           </oneOrMore>
         </element>
       </define>

       <define name="polygon">
         <a:documentation>
           A Polygon from GML.
         </a:documentation>
         <element name="Polygon"
           ns="http://www.opengis.net/gml">
           <attribute name="srsName">
             <value>urn:ogc:def:crs:EPSG::4326</value>
           </attribute>
           <element name="exterior">
             <ref name="linearRing"/>
           </element>
           <zeroOrMore>
             <element name="interior">
               <ref name="linearRing"/>
             </element>
           </zeroOrMore>
         </element>
       </define>

     </div>

   </grammar>

                                 Figure 24














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Authors' Addresses

   Ted Hardie
   Qualcomm, Inc.

   Email: hardie@qualcomm.com


   Andrew Newton
   SunRocket
   8045 Leesburg Pike, Suite 300
   Vienna, VA  22182
   US

   Phone: +1 703 636 0852
   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
   Siemens Networks GmbH & Co KG
   Otto-Hahn-Ring 6
   Munich, Bavaria  81739
   Germany

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












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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

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