Validation of Locations Around a Planned Change
draft-ietf-ecrit-lost-planned-changes-07

ecrit                                                           B. Rosen
Internet-Draft                                               22 May 2023
Intended status: Informational                                          
Expires: 23 November 2023

            Validation of Locations Around a Planned Change
                draft-ietf-ecrit-lost-planned-changes-07

Abstract

   This document defines an extension to the Location to Service
   Translation (LoST) protocol (RFC5222) that allows a LoSR server ti
   notify a client of planned changes to the data.  This extension is
   only useful with the validation function of LoST.  It is beneficial
   for LoST validation clients to be aware of planned changes, as
   records that previously were valid may become invalid at a known
   future date, and new locations may become valid after the date.  This
   extension adds an element to the <findService> request: a date that
   allows the LoST client to request that the server perform validation
   as of the date specified.  It adds an optional Time-To-Live element
   to the response, which informs clients of the current expected
   lifetime of a validation.  It also adds a separate interface to the
   LoST server that allows a client to poll for planned changes.
   Additionally, this document provides a conventional XML schema for
   LoST, as a backwards compatible alternative to the RelaxNG schema in
   RFC5222.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 23 November 2023.

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Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   4
   3.  Planned Change Poll Interface . . . . . . . . . . . . . . . .   4
   4.  <plannedChange> element . . . . . . . . . . . . . . . . . . .   6
   5.  "expires" in Response . . . . . . . . . . . . . . . . . . . .   6
   6.  Replacement XML schema  . . . . . . . . . . . . . . . . . . .   7
   7.  Extension XML Schema  . . . . . . . . . . . . . . . . . . . .  16
   8.  plannedChangePoll Interface Description . . . . . . . . . . .  16
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     10.1.  Replacement XML Schema Registration  . . . . . . . . . .  19
     10.2.  Planned Change Extension XML Schema Registration . . . .  20
   11. Normative References  . . . . . . . . . . . . . . . . . . . .  20
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   Validation of civic locations involves dealing with data that may
   change over time.  A typical example is when a portion of a county or
   district that was not part of a municipality is "annexed" to a
   municipality.  Prior to the change, a Presence Information Data
   Format Location Object (PIDF-LO) [RFC4119] specifying a civic
   location in the affected area would have a blank A3 element, or would
   contain some other value; after the change, a PIDF-LO specifying the
   same location would contain an A3 element set to the name of the
   municipality that annexed that part of the county/district.  This
   kind of annexation has an effective date and time (typically 00:00 on
   the first or last day of a month), known in advance.  Other kinds of
   changes may also occur, and these will almost always also have an
   effective date that is known in advance.

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   Records in a LIS must change around these kinds of events.  The old
   record must be discarded, and a new, validated record must be loaded
   into the LIS.  It is often difficult for the LIS operator to know
   that records must be changed around such events.  There are other
   circumstances where locations that were previously valid become
   invalid, such as a street renaming or renumbering event.  Using
   [RFC5222] validation, the only way for a LIS to discover such changes
   is to periodically revalidate its entire database.  Of course, this
   does not facilitate timely changes, is not coordinated with the
   actual change event, and also adds significant load to the LoST
   server as well as the LIS.  Even if re-validation is contemplated,
   the server has no mechanism to control, or even suggest the time
   period for revalidation.

   This extension allows a LoST client to obtain from the LoST server
   sets of locations which may change.  It makes use of "partial
   location information" which is a set of location elements and values
   that, when compared against the client's location records, identify
   which of the clients records may change as a result of the planned
   change.  A set of such partial locations is termed a "ChangeSet".
   ChangeSets have an ID, and a date when the change is effective.  IDs
   are ordered.  The planned change interface is a REST/JSON interface
   that allows the client to poll the server using the last ID that it
   obtained from that server.  The response to the poll is a list of all
   the newer planned changes the server knows about beyond the ChangeSet
   whose ID was included in the poll.  The ID for the last ChangeSet in
   the returned list will be used by the client for the next poll.

   When a LIS receives a new ChangeSet, it may prepare one or more new
   records so that, at the precise planned event date and time, it may
   insert the new records into in its active database and delete the old
   records.  As part of preparing the new records in advance of the
   change, the LIS may use the "asOf" date component of this extension
   to perform a LoST validation of the new record as of the effective
   date.  In its response, the LoST server may include a new "expires"
   element that expressly states when the location should be re-
   validated, rather than blindly revalidating every address on a
   schedule chosen by the client.

   The "asOf" date component of this extension in a <FindService>
   request allow a LIS to be prepared for and smoothly transition to
   planned changes.  The polling mechanism allows a LIS to be alerted to
   planned changes, while the "asOf" date allows the LIS to verify the
   validity of locations before they become active.

   Unplanned changes will occur, and periodic revalidation can still be
   used to maintain the data in the LIS.  However, the LoST server
   should be able to influence the rate of such revalidation.  For this

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   purpose, this extension adds a "expires" element to the
   <findServiceResponse> which provides advice from the server to the
   LIS of when validation is suggested.

   There are quite a few implementations of LoST.  Experience with these
   implementations indicates that the RelaxNG schema is very difficult
   to deal with, both because many commonly used development tools don't
   support it, and development staff is often unfamiliar with it.
   Informal alternative schemas have been circulated, which is
   undesirable as they may not be in conformance with the RelaxNG schema
   in [RFC5222].  This document provides an XML schema that replaces the
   RelaxNG schema.  It can be used by any implementation interchangeably
   with the RelaxNG schema.

2.  Conventions used in this document

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

   "Server" in this document refers to the LoST server and "Client" is
   the LoST client, even when the server is performing an operation on
   the client.

3.  Planned Change Poll Interface

   This document defines a new interface to the LoST server.  The
   interface has three entry points.  One, Versions, returns the current
   version(s) the interface supports.  This allows the interface to
   evolve over time.  Another entry point, PlannedChangePoll, is a poll.
   The poll returns a list of changeSetIds which identify ChangeSet
   objects.  The third, GetChangeSet, accepts a changeSetId and returns
   the ChangeSet object which contains the identifier (changeSetId), a
   date (changeSetEffective) and an array of partial locations.  A
   partial location is an array of location information element name and
   value pairs.  The client compares the location elements with its
   records.  For each of the clients records where all of the location
   elements provided in the partial location have the same values as
   those in the partial location, that client record may be affected by
   the planned change.  The client's records may have other location
   elements, but those are not considered in the comparison.  So, for
   example, a partial location may have a Country, A1, A2, A3 and A4
   location elements, which means that any address with that Country,
   A1, A2, A3 and A4 values may be affected by the planned change
   regardless of street name and number.  As another example, a partial
   location with Country, A1, A2, A3, A4, RD and POD but not HN means

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   any address number on the specified street.

   The changeSetId is string, which the server maintains as an ordered
   list of changeSetIds.  The id itself may not show the ordering.  For
   example, it could be a hashed timestamp, or a hashed sequence number.
   Given a changeSetId returned by it in a prior poll, the server can
   identify which ChangeSets it has that come after, in order, after the
   one with the proffered changeSetId.  A new client does not know any
   ids, or a client may lose the id that it had.  The client would poll
   omitting the changeSetId in the poll query, and in the response, the
   server returns all the ChangeSets it knows about.  The effective date
   of a ChangeSet returned by the server need not always be in the
   future.  Tardy clients may not keep up.  On the other hand, the
   server is not obligated to keep change sets whose changeSetEffective
   date has passed for more than some arbitrary time.  A 12 month time
   period may be appropriate for a server whose service area doesn't
   have many changes, where a 3 month time period may be needed in a
   fast changing service area where many changes occur regularly.  A
   tardy client in a fast changing environment may receive a large
   number of ChangeSets in response to a poll.

   Polls are expected every few minutes.  A new client omits the ID in
   its first poll, and the server responds with all the changeSetsIds
   that it knows about.  Thereafter, the client retains the last
   changeSetId in its most recent poll and uses that in the next poll.
   If the response to that poll is no changeSetIds, it means the
   changeSetId the client has is the latest change the server knows
   about, and that same changeSetId will be used in subsequent polls
   until the server returns a new one.

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   The version mechanism returns a list of versions of the web service
   it supports.  This document describes version 1.0.  Versions are
   described as a major version and a minor version, where major and
   minor versions are integers.  A backwards compatible change within a
   major version MAY increment only the minor version number.  A non-
   backwards compatible change MUST increment the major version number.
   To achieve backwards compatibility, implementations MUST ignore any
   object members they do not implement.  Minor version definitions
   SHALL only add objects, non-required members of existing objects, and
   non-mandatory-to-use functions and SHALL NOT delete any objects,
   members of objects or functions.  This means an implementation of a
   specific major version and minor version is backwards compatible with
   all minor versions of the major version.  The versions mechanism
   returns an array of supported versions, one for each major version
   supported, with the minor version listed being the highest supported
   minor version.  When versions are written or used as a string, the
   major version is first and separated from the minor version with a
   period.  For example major version 3, minor version 2 would be
   written as "3.2"

4.  <plannedChange> element

   This document defines a new element in the <findService> request
   called "zHxogxRv8SoYre6p1feA7odJF7a0SlwKhPwv".  This element contains
   an attribute: 'asOf' which contains a date and time in dateTime
   format with a required timezone.  The server validates the location
   in the request as of the date and time specified, taking into account
   planned changes.  This allows a client to verify that it can make
   changes in the LIS commensurate with changes in the LoST server by
   validating locations in advance of a change.

5.  "expires" in Response

   This extension adds the 'expires' element to the
   <findServiceResponse>.  The 'expires' element contains a date and
   time after which the client may wish to revalidate the location at
   the server.  A server MAY add this attribute to the response if
   validation is requested.  This element takes the form of the
   'expires' attribute pattern of [RFC5222], which allows the values
   "NO-CACHE" or "NO-EXPIRATION" to be returned instead of a dateTime
   value.  However, for the 'expires'; attribute "NO-CACHE" has no
   meaning and MUST NOT be returned.  "NO-EXPIRATION" means the server
   does not have a suggested revalidation period.

   Selecting a revalidation interval is a complex balancing of
   timeliness, server load, stability of the underlying data, and policy
   of the LoST server.  Too short, and load on the server may overwhelm
   it.  Too long and invalid data may persist in the client for

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   unacceptable lengths of time.  The polling mechanism provides timely
   notice to coordinate changes, but even with it, it is often advisable
   to revalidate data eventually.  In areas that have little change in
   data, such as fully built out, stable communities already part of a
   municipality, it may be reasonable to set revalidation periods of 6
   months or longer, especially if the URI mechanism is widely deployed
   at both the server and the clients.  In areas that are quickly
   growing, 20-30 day revalidation may be more appropriate even though
   such revalidation would be the majority of the traffic on the LoST
   server.

   When a planned change is made, typically the expires value for the
   affected records is lowered, so that revalidation is forced soon
   after the change is implemented.  It is not advisable to set the
   expiration precisely at the planned change time if a large number of
   records will be changed, since that would cause a large spike in
   traffic at the change time.  Rather, the expiration time should have
   a random additional time added to it to spread out the load.

6.  Replacement XML schema

   This schema is an alternative to The Relax NG schema in [RFC5222].
   Future extensions to LoST are expected to use this schema as the base
   for the extensions, rather than the Relax NG schema.  Existing
   extensions described using the Relax NG schema continue to be valid.

   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
              xmlns="urn:ietf:params:xml:ns:lost1"
              targetNamespace="urn:ietf:params:xml:ns:lost1"
              elementFormDefault="qualified">

     <xs:element name="findService">
       <xs:complexType>
         <xs:sequence>
           <xs:group ref="requestLocation"/>
           <xs:group ref="commonRequestPattern"/>
         </xs:sequence>
         <xs:attribute name="validateLocation" type="xs:boolean"/>
         <xs:attribute name="serviceBoundary">
           <xs:simpleType>
             <xs:restriction base="xs:token">
               <xs:enumeration value="reference"/>
               <xs:enumeration value="value"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name="recursive" type="xs:boolean"/>

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       </xs:complexType>
     </xs:element>

     <xs:element name="listServices">
       <xs:complexType>
         <xs:group ref="commonRequestPattern"/>
       </xs:complexType>
     </xs:element>

     <xs:element name="listServicesByLocation">
       <xs:complexType>
         <xs:sequence>
           <xs:group ref="requestLocation"/>
           <xs:group ref="commonRequestPattern"/>
         </xs:sequence>
         <xs:attribute name="recursive" type="xs:boolean"/>
       </xs:complexType>
     </xs:element>

     <xs:element name="getServiceBoundary">
       <xs:complexType>
         <xs:group ref="extensionPoint"/>
         <xs:attributeGroup ref="serviceBoundaryKey"/>
       </xs:complexType>
     </xs:element>

     <xs:element name="findServiceResponse">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="mapping" maxOccurs="unbounded"/>
           <xs:element ref="locationValidation" minOccurs="0"/>
           <xs:group ref="commonResponsePattern"/>
           <xs:group ref="locationUsed"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name="listServicesResponse">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="serviceList"/>
           <xs:group ref="commonResponsePattern"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name="listServicesByLocationResponse">
       <xs:complexType>

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         <xs:sequence>
           <xs:element ref="serviceList"/>
           <xs:group ref="commonResponsePattern"/>
           <xs:group ref="locationUsed"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name="getServiceBoundaryResponse">
       <xs:complexType>
         <xs:sequence>
           <xs:group ref="serviceBoundary"/>
           <xs:group ref="commonResponsePattern"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:group name="commonRequestPattern">
       <xs:sequence>
         <xs:group ref="service"/>
         <xs:element ref="path" minOccurs="0"/>
         <xs:group ref="extensionPoint"/>
       </xs:sequence>
     </xs:group>

     <xs:group name="commonResponsePattern">
       <xs:sequence>
         <xs:element ref="warnings" minOccurs="0" maxOccurs="unbounded"/>
         <xs:element ref="path"/>
         <xs:group ref="extensionPoint"/>
       </xs:sequence>
     </xs:group>

     <xs:group name="requestLocation">
       <xs:sequence>
         <xs:element ref="location" maxOccurs="unbounded"/>
       </xs:sequence>
     </xs:group>

     <xs:element name="location">
       <xs:complexType>
         <xs:complexContent>
           <xs:extension base="locationInformation">
             <xs:attribute name="id" type="xs:token" use="required"/>
           </xs:extension>
         </xs:complexContent>
       </xs:complexType>
     </xs:element>

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     <xs:complexType name="locationInformation">
       <xs:group ref="extensionPoint" maxOccurs="unbounded"/>
       <xs:attribute name="profile" type="xs:NMTOKEN"/>
     </xs:complexType>

     <xs:group name="serviceBoundary">
       <xs:sequence>
         <xs:element ref="serviceBoundary" maxOccurs="unbounded"/>
       </xs:sequence>
     </xs:group>

     <xs:element name="serviceBoundary" type="locationInformation"/>

     <xs:element name="serviceBoundaryReference">
       <xs:complexType>
         <xs:group ref="extensionPoint"/>
         <xs:attributeGroup ref="source"/>
         <xs:attributeGroup ref="serviceBoundaryKey"/>
       </xs:complexType>
     </xs:element>

     <xs:attributeGroup name="serviceBoundaryKey">
       <xs:attribute name="key" type="xs:token" use="required"/>
     </xs:attributeGroup>

     <xs:element name="path">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="via" maxOccurs="unbounded"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name="via">
       <xs:complexType>
         <xs:group ref="extensionPoint"/>
         <xs:attributeGroup ref="source"/>
       </xs:complexType>
     </xs:element>

     <xs:group name="locationUsed">
       <xs:sequence>
         <xs:element ref="locationUsed" minOccurs="0"/>
       </xs:sequence>
     </xs:group>

     <xs:element name="locationUsed">
       <xs:complexType>

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         <xs:attribute name="id" type="xs:token" use="required"/>
       </xs:complexType>
     </xs:element>

     <xs:attributeGroup name="expires">
       <xs:attribute name="expires" use="required">
         <xs:simpleType>
           <xs:union memberTypes="xs:dateTime">
             <xs:simpleType>
               <xs:restriction base="xs:token">
                 <xs:enumeration value="NO-CACHE"/>
               </xs:restriction>
             </xs:simpleType>
             <xs:simpleType>
               <xs:restriction base="xs:token">
                 <xs:enumeration value="NO-EXPIRATION"/>
               </xs:restriction>
             </xs:simpleType>
           </xs:union>
         </xs:simpleType>
       </xs:attribute>
     </xs:attributeGroup>

     <xs:simpleType name="qnameList">
       <xs:list itemType="xs:QName"/>
     </xs:simpleType>

     <xs:element name="mapping">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="displayName"
                minOccurs="0" maxOccurs="unbounded"/>
           <xs:group ref="service"/>
           <xs:choice minOccurs="0">
             <xs:group ref="serviceBoundary"/>
             <xs:element ref="serviceBoundaryReference"/>
           </xs:choice>
           <xs:element ref="uri"
                minOccurs="0" maxOccurs="unbounded"/>
           <xs:element ref="serviceNumber" minOccurs="0"/>
           <xs:group ref="extensionPoint"/>
         </xs:sequence>
         <xs:attributeGroup ref="expires"/>
         <xs:attribute name="lastUpdated" type="xs:dateTime"
               use="required"/>
         <xs:attributeGroup ref="source"/>
         <xs:attribute name="sourceId" type="xs:token"
               use="required"/>

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         <xs:attributeGroup ref="message"/>
       </xs:complexType>
     </xs:element>

     <xs:element name="displayName">
       <xs:complexType>
         <xs:simpleContent>
           <xs:extension base="xs:string">
             <xs:attribute ref="xml:lang" use="required"/>
           </xs:extension>
         </xs:simpleContent>
       </xs:complexType>
     </xs:element>

     <xs:element name="uri" type="xs:anyURI"/>

     <xs:element name="serviceNumber">
       <xs:simpleType>
         <xs:restriction base="xs:token">
           <xs:pattern value="[0-9*#]+"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:element>

     <xs:element name="locationValidation">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="valid" minOccurs="0"/>
           <xs:element ref="invalid" minOccurs="0"/>
           <xs:element ref="unchecked" minOccurs="0"/>
           <xs:group ref="extensionPoint"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name="valid" type="qnameList"/>

     <xs:element name="invalid" type="qnameList"/>

     <xs:element name="unchecked" type="qnameList"/>

     <xs:complexType name="exceptionContainer">
       <xs:sequence>
         <xs:choice minOccurs="0" maxOccurs="unbounded">
           <xs:element ref="badRequest"/>
           <xs:element ref="internalError"/>
           <xs:element ref="serviceSubstitution"/>
           <xs:element ref="defaultMappingReturned"/>

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           <xs:element ref="forbidden"/>
           <xs:element ref="notFound"/>
           <xs:element ref="loop"/>
           <xs:element ref="serviceNotImplemented"/>
           <xs:element ref="serverTimeout"/>
           <xs:element ref="serverError"/>
           <xs:element ref="locationInvalid"/>
           <xs:element ref="locationProfileUnrecognized"/>
         </xs:choice>
         <xs:group ref="extensionPoint"/>
       </xs:sequence>
       <xs:attributeGroup ref="source"/>
     </xs:complexType>

     <xs:element name="errors" type="exceptionContainer"/>

     <xs:element name="warnings" type="exceptionContainer"/>

     <xs:complexType name="basicException">
       <xs:annotation>
         <xs:documentation>
           Exception pattern.
         </xs:documentation>
       </xs:annotation>
       <xs:group ref="extensionPoint"/>
       <xs:attributeGroup ref="message"/>
     </xs:complexType>

     <xs:element name="badRequest" type="basicException"/>

     <xs:element name="internalError" type="basicException"/>

     <xs:element name="serviceSubstitution" type="basicException"/>

     <xs:element name="defaultMappingReturned" type="basicException"/>

     <xs:element name="forbidden" type="basicException"/>

     <xs:element name="notFound" type="basicException"/>

     <xs:element name="loop" type="basicException"/>

     <xs:element name="serviceNotImplemented" type="basicException"/>

     <xs:element name="serverTimeout" type="basicException"/>

     <xs:element name="serverError" type="basicException"/>

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     <xs:element name="SRSinvalid" type="basicException"/>

     <xs:element name="locationInvalid" type="basicException"/>

     <xs:element name="locationValidationUnavailable"
             type="basicException"/>

     <xs:element name="locationProfileUnrecognized">
             type="basicException"/>

     <xs:element name="redirect">
       <xs:complexType>
         <xs:group ref="extensionPoint"/>
         <xs:attribute name="target" type="appUniqueString"
             use="required"/>
         <xs:attributeGroup ref="source"/>
         <xs:attributeGroup ref="message"/>
       </xs:complexType>
     </xs:element>

     <xs:attributeGroup name="message">
       <xs:attribute name="message" type="xs:token"/>
       <xs:attribute ref="xml:lang"/>
     </xs:attributeGroup>

     <xs:group name="service">
       <xs:sequence>
         <xs:element ref="service" minOccurs="0"/>
       </xs:sequence>
     </xs:group>

     <xs:element name="service" type="xs:anyURI"/>

     <xs:simpleType name="appUniqueString">
       <xs:restriction base="xs:token">
         <xs:pattern value="([a-zA-Z0-9\-]+\.)+[a-zA-Z0-9]+"/>
       </xs:restriction>
     </xs:simpleType>

     <xs:attributeGroup name="source">
       <xs:attribute name="source" type="appUniqueString" use="required"/>
     </xs:attributeGroup>

     <xs:element name="serviceList">
       <xs:simpleType>
         <xs:list itemType="xs:anyURI"/>
       </xs:simpleType>
     </xs:element>

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     <xs:group name="notLost">
       <xs:annotation>
         <xs:documentation>
           Any element not in the LoST namespace.
         </xs:documentation>
       </xs:annotation>
       <xs:choice>
         <xs:any namespace="##other" processContents="skip"/>
         <xs:any namespace="##local" processContents="skip"/>
       </xs:choice>
     </xs:group>

     <xs:group name="anyElement">
       <xs:annotation>
         <xs:documentation>
           A wildcard pattern for including any element
           from any other namespace.
         </xs:documentation>
       </xs:annotation>
       <xs:sequence>
         <xs:any processContents="skip"
             minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
     </xs:group>

     <xs:attributeGroup name="anyElement">
       <xs:annotation>
         <xs:documentation>
           A wildcard pattern for including any element
           from any other namespace.
         </xs:documentation>
       </xs:annotation>
       <xs:anyAttribute processContents="skip"/>
     </xs:attributeGroup>

     <xs:group name="extensionPoint">
       <xs:annotation>
         <xs:documentation>
           A point where future extensions
           (elements from other namespaces)
           can be added.
         </xs:documentation>
       </xs:annotation>
       <xs:sequence>
         <xs:group ref="notLost"
              minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
     </xs:group>

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   </xs:schema>

7.  Extension XML Schema

   This schema provides the extension to the prior section schema for
   planned changes:

   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
              xmlns="urn:ietf:params:xml:ns:lostPlannedChange1"
              targetNamespace="urn:ietf:params:xml:ns:lostPlannedChange1"
              elementFormDefault="qualified">
        <!-- Import base Lost -->
        <xs:import namespace="urn:ietf:params:xml:ns:lost1"/>
   <!-- extend the extensionPoint of commonRequestPattern of findService
                                       to include:  -->
         <xs:element ref="asOf" type="xs:dateTime" minOccurs="1"/>

   <!-- extend the extensionPoint of commonResponsePattern in
                    findServiceResponse to include: -->
         <xs:element ref="expires" type="xs:dateTime" minOccurs="0" />

   </xs:schema>

8.  plannedChangePoll Interface Description

         openapi: 3.0.1
           info:
             title: LoST plannedChange
             version: "1.0"
           servers:
             - url: http://localhost/LoST/v1
           paths:
             /PlannedChangePoll:
               get:
                 summary: Get a list of planned changeSetIds
                 operationId: getPlannedChangeIds
                 responses:
                   '200':
                     description: Planned Changes
                     content:
                       application/json:
                         schema:
                           $ref: '#/components/schemas/PlannedChangeIdList'

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             /GetChangeSet:
               get:
                 summary: Get a ChangeSet
                 operationId: getChangeSet
                 parameters:
                   - in: query
                     name: changeSetId
                     schema:
                       type: string
                     description: Id of a ChangeSet
                 responses:
                   '200':
                     description: return ChangeSet object
                     content:
                       application/json:
                         schema:
                           $ref: '#/components/schemas/ChangeSet'
             /Versions:
               servers:
                 - url: https://api.example.com/rum
                   description: Override base path for Versions query
               get:
                 summary: Retrieves all supported versions
                 operationId: RetrieveVersions
                 responses:
                   '200':
                     description: Versions supported
                     content:
                       application/json:
                         schema:
                           $ref: '#/components/schemas/VersionsArray'
           components:
             schemas:
               PlannedChangeIdList:
                 type: array
                 items:
                   type: string
               ChangeSet:
                 type: object
                 properties:
                   changeSetId:
                     type: string
                     description: Id of the ChangeSet
                   changeSetEffective:
                     type: string
                     format: datetime
                     description: date and time change will come into
                        effect in dateTime format with a required timezone

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                   partialLocationList:
                     type: array
                     items:
                       type: object
                       properties:
                         caType:
                           type: string
                           description: CAtype name from IANA registry
                         value:
                           type: string
                           description: value for this caType
               VersionsArray:
                 type: object
                 required:
                   - versions
                 properties:
                   versions:
                     type: array
                     items:
                       type: object
                       required:
                         - major
                         - minor
                       properties:
                         major:
                           type: integer
                           format: int32
                           description: Version major number
                         minor:
                           type: integer
                           format: int32
                           description: Version minor number

9.  Security Considerations

   As an extension to LoST, this document inherits the security issues
   raised in [RFC5222].  The server could be tricked into storing a
   malicious URI which, when sent the revalidateLocation object could
   trigger something untoward.  The server MUST NOT accept any data from
   the client in response to POSTing the revalidateLocation.

   The server is subject to abuse by clients because it is being asked
   to store something and may need to send data to an uncontrolled URI.
   Clients could request many URIs for the same location, for example.
   The server MUST have policy that limits use of this mechanism by a
   given client.  If the policy is exceeded, the server returns the
   <uriNotStored> warning.  The server MUST validate that the content of
   the 'uri' attribute sent is syntactically valid and meets the 256

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   bytes limit.  When sending the <revalidateLocation> object to the URI
   stored, the server MUST protect itself against common HTTP
   vulnerabilities.

   The mutual authentication between client and server is RECOMMENDED
   for both the initial <findServiceRequest> operation that requests
   storing the URI and the sending of the <revalidateLocation> object.
   The server should be well known to the client, and its credential
   should be learned in a reliable way.  For example, a public safety
   system operating the LoST server may have a credential traceable to a
   well known Certificate Authority known to provide credentials for
   public safety agencies.  Clients may be operated by local ISPs or
   other service providers that can reasonably obtain a good credential
   to use for the server side of the LoST server's POST transaction
   using the URI.  Where the loST server does not recognize the client,
   its policy MAY limit the use of this feature beyond what it would
   limit a client it recognizes.

10.  IANA Considerations

10.1.  Replacement XML Schema Registration

    URI:  urn:ietf:params:xml:schema:lost3
    Registrant Contact:  IETF ECRIT Working Group, Brian Rosen
       (br@brianrosen.net).
    XML:
       BEGIN
       <?xml version="2.0"?>
       <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
       "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"&gt;
       <html xmlns="http://www.w3.org/1999/xhtml"&gt;
       <head&gt;
       <meta http-equiv="content-type"
           content="text/html;charset=iso-8859-1"/&gt;
       <title&gt;LoST Namespace</title&gt;
       </head&gt;
       <body&gt;
       <h1&gt;Namespace for LoST</h1&gt;
       <h2&gt;urn:ietf:params:xml:ns:lost3</h2&gt;
       <p&gt;See <a href="http://www.rfc-editor.org/rfc/rfc????.txt"&gt;
       RFC????</a&gt;.</p&gt;
       </body&gt;
       </html&gt;
       END

   The XML Schema is found in Section 6.

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10.2.  Planned Change Extension XML Schema Registration

      URI:  urn:ietf:params:xml:schema:lostPlannedChange1
      Registrant Contact:  IETF ECRIT Working Group, Brian Rosen
         (br@brianrosen.net).
      XML:

      BEGIN
      <?xml version="2.0"?>
      <!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 Planned Change Namespace</title>
      </head>
      <body>
        <h1>Namespace for LoST </h1>
        <h2>urn:ietf:params:xml:ns:lostPlannedChange1</h2>
      <p>See <a href="http://www.rfc-editor.org/rfc/rfc????.txt">
         RFC????</a>.</p>
      </body>
      </html>
      END

   The XML Schema is found in Section 7.

11.  Normative References

   [RFC4119]  Peterson, J., "A Presence-based GEOPRIV Location Object
              Format", RFC 4119, DOI 10.17487/RFC4119, December 2005,
              <https://www.rfc-editor.org/info/rfc4119>.

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

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

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

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Author's Address

   Brian Rosen
   Email: br@brianrosen.net

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