| Internet-Draft | Returned Location Extensions to LoST | August 2021 |
| Rosen, et al. | Expires 19 February 2022 | [Page] |
This document introduces a new way to provide returned location information in LoST responses that is either of a completed or similar form to the original input civic location, based on whether valid or invalid civic address elements are returned within the findServiceResponse message. This document defines a new extension to the findServiceResponse message within the LoST protocol [RFC5222] that enables the LoST protocol to return a completed civic address element set for a valid location response, and one or more suggested sets of similar location information for invalid LoST responses. These two types of civic addresses are referred to as either "complete location" or "similar location", and are included as a compilation of CAtype xml elements within the existing LoST findServiceResponse message structure.¶
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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.¶
The LoST protcol [RFC5222] supports the validation of civic location information as input, by providing a set of validation result status indicators. The current usefulness of the supported xml elements, "valid", "invalid", and "unchecked", is limited, because while they each provide an indication of validity for any one location element as a part of the whole civic address, the mechanism is insufficient in providing either the complete set of civic address elements that the LoST server contains, or of providing alternate suggestions (hints) as to which civic address is intended for use.¶
Whether the input civic location is valid but missing information, or invalid due to missing or wrong information during input, this document provides a mechanism to return a complete set of civic address elements for those valid or invalid cases.¶
This enhancement to the validation feature within LoST is required by systems that rely on accurate location for processing. Use of this enhancement increases the likelihood that the correct and/or complete form of a civic location becomes known in those cases where it is incomplete or incorrect. One such use case is that of location based emergency calling. The use of this protocol extension facilitates the correction of errors, and allows location servers to be more easily provisioned with complete address information.¶
The structure of this document includes terminology, Section 2, followed by a discussion of the basic elements involved in location validation. The use of these elements, by way of example, is discussed in an overview section, Section 3, with accompanying rationale, and a brief discussion of the impacts to LoST, and its current schema.¶
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 RFC 2119 [RFC2119].¶
The following terms are defined in this document:¶
This document describes an extension to LoST [RFC5222] to allow additional location information to be returned in the locationValidation element of a findServiceResponse. This extension is applicable when the location information in the findServiceRequest is in a civic profile as described in RFC5222 or in another profile derived from that civic profile. This extension has two different use cases: first, when the input location is incomplete but the LoST server can identify the intended unique address, and second, when the input location is invalid and the LoST server can identify one or more likely intended locations.¶
When a LoST server is asked to validate a civic location, its goal is to take the set of civic address elements provided as the location information in the LoST request, and find a unique location in its database that matches the information in the request. Uniqueness might not require values for all possible elements in the civic address that the database might hold. Further, the input location information might not represent the form of location the users of the LoST service prefer to have. As an example, there are LoST civic address elements that could be used to define a postal location, suitable for delivery of mail as well as a municipal location suitable for responding to an emergency call. While the LoST server might be able to determine the location from the postal elements provided, the emergency services would prefer that the municipal location be used for any subsequent emergency call. Since validation is often performed well in advance of an end-user placing an emergency call, if the LoST server could return the preferred form of location (or more properly in this example, the municipal elements in addition to the postal elements), those elements could be stored in a LIS or client application and used in a later emergency call.¶
In addition, this document describes the reuse of the same mechanism, but for a different purpose: to supply similar location information in the case where a LoST server response includes one or more civic address elements marked as invalid, constituting an invalid location response. In this case, the response contains one or more suggested alternative valid locations.¶
In a LoST findServiceResponse indicating a valid location -- i.e., containing a locationValidation element with no elements listed as invalid -- the LoST server can use this extension to include additional location information in a locationValidation element. As an example, the query might contain a HNO (house number), RD (road name) A3 (city), At (state/province) and a few more CAtype elements, but might not contain A2 (county) or PC (Postal Code) CAtypes. The civic location in the request might contain HNO, RD, STS, POD, A3 and A1 civic address elements that are sufficient enough for the LoST server to uniquely locate the address specified in the request and thus be considered valid. Yet, other entities involved in a subsequent emergency call might find it helpful to have additional civic address elements such as A2 (county), PC, (Postal Code) be included as part of a complete civic location. Since [RFC5222] currently does not have a way for this additional location information to be returned in the findServiceResponse, this document extends the LoST protocol so that it can include a completeLocation element within the locationValidation element of the findServiceResponse message, allowing for the representation of complete location information.¶
An example showing complete location information supplied:¶
input address: 6000 15th Ave NW Seattle¶
complete location: 6000 15th Ave NW Seattle, WA 98105 US¶
The information provided in the request may be enough to identify a unique location in the LoST server, but that may not be the location intended by the user. The completeLocation information may alert the user to a mismatch between the provided location information and the unique location the server interpreted that information to identify.¶
The other use case for this extension is when invalid location is received from the LoST server. When a LoST server returns a response to a findService request that contains a set of civic address elements with one or more labeled as invalid, the location information in the findServiceResponse can be extended to include one or more locations that might be the location desired.¶
In the example cited above, policy at the LoST server might deem a missing A3 element as invalid, even if the location information in the request was sufficient to identify a unique address. In that case, the missing element would be listed in the invalid list, and a similarLocation element could be returned in the response showing a complete civic location that includes the missing A3 element, just as in the above example.¶
As another example of the use of similarLocation, consider the results based on a similar data set as used above, where the HNO, RD, STS, A1, and A3 civic address elements are not sufficient to locate a unique address, which leads to an invalid location result. Because the LoST server typically contains additional civic address elements which could have resulted in a uniquely identifiable location if these additional element had been included in the location sent in the query. Since [RFC5222] currently does not have a way for this additional location information to be returned in the findServiceResponse, this document extends [RFC5222] so that the LoST locationValidation element of the findServiceResponse message can include one or more similarLocation elements representing similar civic locations.¶
To show this, suppose that a slightly modified version of the above address is sent within a Lost findService request:¶
input address: 6000 15th Ave N Seattle, WA.¶
This time we make the assumption that the address is deemed "invalid" by the LoST server because there is no such thing as "15th Ave N" within the LoST server's data for the city of Seattle. However, we also happen to know for this example that there are two addresses within the address dataset that are "similar", when all parts of the address are taken as a whole. These similar addresses that could be returned to the client are as follows:¶
similar address #1: 6000 15th Ave NW Seattle, WA 98107¶
similar address #2: 6000 15th Ave NE Seattle, WA 98105¶
This extension allows the LoST server to include the above similar addresses in the response to locationValidation. The next section shows examples of the LoST request and response XML message fragments for the above valid and invalid scenarios, returning the complete or similar addresses respectively.¶
The LoST server implementing this extension MAY include completeLocation or similarLocation elements within the locationValidation portion of the findService response. The completeLocation and similarLocation elements contain a list of civic address elements identical to the elements used in the location element with the "civic profile" in [RFC5222] or another profile derived from the civic profile.¶
The LoST server MAY include more than one similarLocation element in the response. If there are too many possible locations, the server MAY return none, or it MAY return a subset considered most likely. How many to return is left to the implementation of the LoST server. The server is unable to know what the intended location information was suppose to be; it is guessing. Therefore the correct location may or may not be one of the similarLocation elements the server provides, and the client cannot assume that any of them are the correct location.¶
Where a LoST server contains additional location information relating to the civic address used in a findServiceRequest, the findServiceResponse message MAY include a completeLocation element containing additional location information along with the original validated civic address elements; the additional civic address elements may be deemed by local policy as necessary to form a complete location. The completeLocation element MUST NOT be returned in response messages where any civic address elements occur in the invalid list of the response, or where the set of civic address elements in the request do not identify a unique location. The complete location MUST NOT contain any elements that would be marked as invalid, or cause an error, if a recipient of that location performs a subsequent findService request using the complete location. However, if a subsequent request includes the complete location, the corresponding request MAY include elements in the unchecked list.¶
Clients can control the return of additional location information by including an optional returnAdditionalLocation attribute with possible values "none", "similar", "complete" or "any". The value "none" means to not return additional location information, "similar" and "complete" mean to only return the respective type of additional location information (if the server could send any) and "any" means to include similar and/or complete location (if the server could send any). If the request includes this attribute, the server MUST NOT send location information contravening the client's request. Omitting this attribute in the request is equivalent to including it with the value "none".¶
The server may determine that there are many possible similar locations and decide not to send them all. The number of similar locations sent is entirely up to the server. The server MAY include a similarLocationsLimited attribute which contains a non-zero integer indicating the number of similar locations not included in the response. The server is NOT obligated to make this number accurate, in that there may be more than the indicated similar locations available in the data held by the server.¶
Clients MAY ignore the location information this extension defines. The information is optional to send, and optional to use. In the case where the location information in the request was valid, this extension does not change the validity. In the case where the location information in the request is invalid, but alternate location information is returned, the original location remains invalid, and the LoST server does not change the mapping response other than optionally including the information defined by this extension.¶
The completeLocation and similarLocation elements use the locationInformation element from [RFC5222] updated by [I-D.ietf-ecrit-lost-planned-changes], including the profile attribute, which is useful if the request contains location information in a profile derived from the civic profile. The profile attribute MUST be included in both the request and the response and MUST be the same profile in both.¶
Based on the example input request above, returned location information is provided in a findServiceResponse message since the original input address is considered valid but is missing some additional data that the LoST server has.¶
<!-- =====Request=================================== -->
<findService xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:rli="urn:ietf:params:xml:ns:lost-rli1"
validateLocation="true" rli:returnAdditionalLocation="any">
<location id="587cd3880" profile="civic">
<civicAddress
xmlns="urn:ietf:params:mxl:ns:pidf:geopriv10:civicAddr">
<country>US</country>
<A1>WA</A1>
<A3>Seattle</A3>
<RD>15th</RD>
<STS>Avenue</STS>
<POD>Northwest</POD>
<HNO>6000</HNO>
</civicAddress>
</location>
<service>urn:service:sos</service>
</findService>
<!-- =====Response================================== -->
<findServiceResponse >
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:rli="urn:ietf:params:xml:ns:lost-rli1">
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
<mapping
expires="NO-CACHE"
lastUpdated="2006-11-01T01:00:00Z"
source="authoritative.example"
sourceId="8799e346000098aa3e">
<displayName xml:lang="en">Seattle 911</displayName>
<service>urn:service:sos</service>
<uri>sip:seattle-911@example.com</uri>
<serviceNumber>911</serviceNumber>
</mapping>
<locationValidation>
<valid>ca:country ca:A1 ca:A3 ca:RD ca:STS ca:POD ca:HNO
</valid>
<invalid></invalid>
<unchecked></unchecked>
<rli:completeLocation profile="civic"><!--completed address-->
<ca:civicAddress>
<ca:country>US</ca:country>
<ca:A1>WA</ca:A1>
<ca:A2>KING COUNTY</ca:A2>
<ca:A3>SEATTLE</ca:A3>
<ca:RD>15TH</ca:RD>
<ca:STS>AVENUE</ca:STS>
<ca:POD>NORTHWEST</ca:POD>
<ca:HNO>6000</ca:HNO>
<ca:PC>98106</ca:PC>
<ca:PCN>SEATTLE</ca:PCN>
</ca:civicAddress>
</rli:completeLocation>
</locationValidation>
<path>
<via source="authoritative.example"/>
</path>
<locationUsed id="587cd3880"/>
</findServiceResponse>
<!-- =============================================== -->
¶
The following example shows two returned similar locations in a findServiceResponse message when the original input address is considered invalid, in this example because the LoST server needed the omitted POD data to match a unique address.¶
<!-- =====Request=================================== -->
<findService xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:rli="urn:ietf:params:xml:ns:lost-rli1"
validateLocation="true"
rli:returnAdditionalLocation="any">
<location id="587cd3880" profile="civic">
<civicAddress
xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
<country>US</country>
<A1>WA</A1>
<A2>KING COUNTY</A2>
<A3>SEATTLE</A3>
<RD>15TH</RD>
<STS>AVENUE</STS>
<HNO>6000</HNO>
<PC>98106</PC>
<PCN>SEATTLE</PCN>
</civicAddress>
</location>
<service>urn:service:sos</service>
</findService>
<!-- =====Response=================================== -->
<findServiceResponse>
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:rli="urn:ietf:params:xml:ns:lost-rli1">
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
<mapping
expires="NO-CACHE"
lastUpdated="2006-11-01T01:00:00Z"
source="authoritative.example"
sourceId="8799e346000098aa3e">
<displayName xml:lang="en">Seattle 911</displayName>
<service>urn:service:sos</service>
<uri>sip:seattle-911@example.com</uri>
<serviceNumber>911</serviceNumber>
</mapping>
<locationValidation>
<valid>ca:country ca:A1 ca:A3 ca:STS ca:RD</valid>
<invalid>ca:POD</invalid>
<unchecked>ca:HNO</unchecked>
<rli:similarLocation profile="civic"><!--similar location-->
<ca:civicAddress> <!-- similar address #1 -->
<ca:country>US</ca:country>
<ca:A1>WA</ca:A1>
<ca:A2>KING COUNTY</ca:A2>
<ca:A3>SEATTLE</ca:A3>
<ca:RD>15TH</ca:RD>
<ca:STS>AVENUE</ca:STS>
<ca:POD>NORTHWEST</ca:POD>
<ca:HNO>6000</ca:HNO>
<ca:PC>98106</ca:PC>
<ca:PCN>SEATTLE</ca:PCN>
</ca:civicAddress>
</rli:similarLocation>
<rli:similarLocation profile="civic">
<ca:civicAddress> <!-- similar address #2 -->
<ca:country>US</ca:country>
<ca:A1>WA</ca:A1>
<ca:A2>KING COUNTY</ca:A2>
<ca:A3>SEATTLE</ca:A3>
<ca:RD>15TH</ca:RD>
<ca:STS>AVENUE</ca:STS>
<ca:POD>NORTHEAST</ca:POD>
<ca:HNO>6000</ca:HNO>
<ca:PC>98105</ca:PC>
<ca:PCN>SEATTLE</ca:PCN>
</ca:civicAddress>
</rli:similarLocation>
</locationValidation>
<path>
<via source="authoritative.example"/>
</path>
<locationUsed id="587cd3880"/>
</findServiceResponse>
<!-- =============================================== -->
¶
This section provides the schema of the LoST extensions, based on the schema in [I-D.ietf-ecrit-lost-planned-changes]¶
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:lost1="urn:ietf:params:xml:ns:lost1"
xmlns="urn:ietf:params:xml:ns:lost-rli1”
targetNamespace="urn:ietf:params:xml:ns:lost-rli1"
elementFormDefault="qualified">
<!-- Import base Lost -->
<xs:import namespace="urn:ietf:params:xml:ns:lost1"/>
<!-- extend findService by placing the following
at the extensionPoint
in the included commonRequestPattern: -->
<xs:attribute name="returnAdditionalLocation" use="optional">
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:enumeration value="none"/>
<xs:enumeration value="similar"/>
<xs:enumeration value="complete"/>
<xs:enumeration value="any"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<!-- extend locationValidation by placing the following
at the extensionPoint -->
<group>
<xs:choice minOccurs="0">
<xs:element name="similarLocation"
type="lost1:locationInformation"
minOccurs="1" maxOccurs="unbounded" />
<xs:element name="completeLocation"
type="lost1:locationInformation"/>
</xs:choice>
</group>
<!-- and also at the locationValidation extensionPoint -->
<xs:attribute name="similarLocationsLimited" use="optional">
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:minInclusive value="1">
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:schema>
¶
Whether the input to the LoST server is a valid or invalid location, the LoST server ultimately determines what it considers to be a valid location. Even in the case where the input location is valid, the requester still might not actually understand where that location is. For this kind of valid location use case, this extension would typically return more location information than what the requester started with, which might reveal to the requester additional information (additional CAtypes) about the location. While this is very desirable in some scenarios such as supporting an emergency call, it might not be as desirable for other services. Individual LoST server implementations SHOULD consider the risk of releasing more detail versus the value in doing so. Generally, supplying more information (CAtypes) is not considered to be a significant problem because the requester has to already have enough information for the location to be considered valid, which in most cases is enough to uniquely locate the address. Providing more CAtypes generally doesn't actually reveal anything more. When invalid locations are submitted, this extension allows the LoST response to include locations that are similar to what was input, again resulting in more information provided in the response than was sent in the request. LoST server implementations SHOULD evaluate the particular use cases where this extension is supported, and weigh the risks around its use. Many services available today via the Internet offer similar features, such as "did you mean" or address completion, so this capability is not introducing any fundamentally new threat.¶
URI: urn:ietf:params:xml:schema:lost-rli1
Registrant Contact: IETF ECRIT Working Group, Brian Rosen
(br@brianrosen.net).
XML Schema: The XML schema to be registered is contained
in Section 7.
¶
URI: urn:ietf:params:xml:ns:lost-rli1
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 Returned Location Information Namespace</title>
</head>
<body>
<h1>Namespace for LoST Returned Location Information extension</h1>
<h2>urn:ietf:params:xml:ns:lost-rli1</h2>
<p>See <a href="http://www.rfc-editor.org/rfc/rfc????.txt">
RFC????</a>.</p>
</body>
</html>
END
¶