ecrit                                                           B. Rosen
Internet-Draft                                           11 October 2021
Updates: RFC5222 (if approved)
Intended status: Standards Track
Expires: 14 April 2022


            Validation of Locations Around a Planned Change
                draft-ietf-ecrit-lost-planned-changes-05

Abstract

   This document defines an extension to the Location to Service
   Translation (LoST) protocol (RFC5222) that allows planned changes to
   the data to be handled smoothly.  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 14 April 2022.







Rosen                     Expires 14 April 2022                 [Page 1]


Internet-Draft            LoST Planned Changes              October 2021


Copyright Notice

   Copyright (c) 2021 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 Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   4
   3.  Planned Change Poll Interface . . . . . . . . . . . . . . . .   4
   4.  <plannedChange> element . . . . . . . . . . . . . . . . . . .   6
   5.  Time-To-Live (TTL) in Response  . . . . . . . . . . . . . . .   6
   6.  Replacement XML schema  . . . . . . . . . . . . . . . . . . .   7
   7.  Extension XML Schema  . . . . . . . . . . . . . . . . . . . .  15
   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  . . . . . . . . . . . . . . . . . . . .  21
   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) 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.





Rosen                     Expires 14 April 2022                 [Page 2]


Internet-Draft            LoST Planned Changes              October 2021


   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 "as of" date component of this extension
   to perform a LoST validation of the new record as of the effective
   date.

   The "asOf" date component of this extension in a <FindService>
   request allow a LIS to be prepared for and smoothly transition to
   planned changes, without the overhead and delay inherent in
   performing periodic revalidation of each location.  The notification
   URI allows a LIS to be alerted to planned changes, while the "as of"
   date allows the LIS to verify the validity of locations before they
   become active.

   In situations where it is not practical or advisable for the LIS to
   maintain a stable URI for each of its records, 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.



Rosen                     Expires 14 April 2022                 [Page 3]


Internet-Draft            LoST Planned Changes              October 2021


   For this purpose, this extension adds a Time to Live (TTL) attribute
   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", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   "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
   any address number on the specified street.




Rosen                     Expires 14 April 2022                 [Page 4]


Internet-Draft            LoST Planned Changes              October 2021


   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 it 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 whoose changeSetEffective
   date has past 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 recieve a large
   number of ChangSets 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.

   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, the period "." 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.







Rosen                     Expires 14 April 2022                 [Page 5]


Internet-Draft            LoST Planned Changes              October 2021


4.  <plannedChange> element

   This document defines a new element in the <findService> request
   called "plannedChange".  This element contains an attribute: 'asOf'.
   The 'asOf' attribute 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.  Time-To-Live (TTL) in Response

   This extension adds the 'ttl' element to the <findServiceResponse>.
   The 'ttl'; 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 'ttl';
   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 server for
   unacceptable lengths of time.  The URI notification 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 TTL 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.




Rosen                     Expires 14 April 2022                 [Page 6]


Internet-Draft            LoST Planned Changes              October 2021


6.  Replacement XML schema

   This schema is an alternative to The Relax NG schema in [RFC5222].
   Future extensions to LoST are exected 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"/>
     </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>




Rosen                     Expires 14 April 2022                 [Page 7]


Internet-Draft            LoST Planned Changes              October 2021


   <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>
       <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>



Rosen                     Expires 14 April 2022                 [Page 8]


Internet-Draft            LoST Planned Changes              October 2021


       <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>

   <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"/>



Rosen                     Expires 14 April 2022                 [Page 9]


Internet-Draft            LoST Planned Changes              October 2021


     </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>
       <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>



Rosen                     Expires 14 April 2022                [Page 10]


Internet-Draft            LoST Planned Changes              October 2021


         </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"/>
       <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>



Rosen                     Expires 14 April 2022                [Page 11]


Internet-Draft            LoST Planned Changes              October 2021


       <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"/>
         <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"/>




Rosen                     Expires 14 April 2022                [Page 12]


Internet-Draft            LoST Planned Changes              October 2021


   <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"/>

   <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>



Rosen                     Expires 14 April 2022                [Page 13]


Internet-Draft            LoST Planned Changes              October 2021


   </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>

   <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.



Rosen                     Expires 14 April 2022                [Page 14]


Internet-Draft            LoST Planned Changes              October 2021


       </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>

 </xs:schema>

7.  Extension XML Schema

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













Rosen                     Expires 14 April 2022                [Page 15]


Internet-Draft            LoST Planned Changes              October 2021


 <?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:group ref="plannedChange" minOccurs="1"/>

 <!-- where -->
        <xs:group name="plannedChange">
            <xs:sequence>
               <xs:element ref="asOf" type="xs:dateTime" minOccurs=
               "1"/>
               <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
            </xs:sequence>
         </xs:group>

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

 <!-- extend the extensionPoint of extensionContainer to include: -->
            <xs:element ref="uriNotStored"/>
 <!-- where -->
            <xs:element name="uriNotStored" type="basicException"/>



 </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:



Rosen                     Expires 14 April 2022                [Page 16]


Internet-Draft            LoST Planned Changes              October 2021


                '200':
                  description: Planned Changes
                  content:
                    application/json:
                      schema:
                        $ref: '#/components/schemas/PlannedChangeIdList'
          /GetChangeSet:
            get:
              summary: Get a changeSet
              operationId: getChangeSet
              parameters:
                - in: query
                  name: changeSetId
                  schema:
                    type: string
                  description: Id of a changeSet
              responses:
                '200':
                  description: 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



Rosen                     Expires 14 April 2022                [Page 17]


Internet-Draft            LoST Planned Changes              October 2021


                  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
                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.





Rosen                     Expires 14 April 2022                [Page 18]


Internet-Draft            LoST Planned Changes              October 2021


   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
   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























Rosen                     Expires 14 April 2022                [Page 19]


Internet-Draft            LoST Planned Changes              October 2021


      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">
         <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:lost3</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 6.

10.2.  Planned Change Extension XML Schema Registration

























Rosen                     Expires 14 April 2022                [Page 20]


Internet-Draft            LoST Planned Changes              October 2021


      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

   [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>.

   [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>.

Author's Address

   Brian Rosen
   470 Conrad Dr
   Mars, PA 16046
   United States of America

   Email: br@brianrosen.net




Rosen                     Expires 14 April 2022                [Page 21]