6848
PROPOSED STANDARD
Specifying Civic Address Extensions in the Presence Information Data Format Location Object (PIDF-LO)
Authors: J. Winterbottom, M. Thomson, R. Barnes, B. Rosen, R. George
Date: January 2013
Area: rai
Working Group: geopriv
Stream: IETF
Updates:
RFC 4776
Abstract
New fields are occasionally added to civic addresses. A backward- compatible mechanism for adding civic address elements to the Geopriv civic address format is described. A formal mechanism for handling unsupported extensions when translating between XML and DHCP civic address forms is defined for entities that need to perform this translation. Initial extensions for some new elements are also defined. The Location-to-Service Translation (LoST) protocol mechanism (defined in RFC 5222) that returns civic address element names used for validation of location information is clarified and is normatively updated to require a qualifying namespace identifier on each civic address element returned as part of the validation process. [STANDARDS-TRACK]
RFC 6848
PROPOSED STANDARD
Internet Engineering Task Force (IETF) J. Winterbottom
Request for Comments: 6848 CommScope
Updates: <a href="./rfc4776">4776</a>, <a href="./rfc5222">5222</a> M. Thomson
Category: Standards Track Skype
ISSN: 2070-1721 R. Barnes
BBN Technologies
B. Rosen
NeuStar, Inc.
R. George
Huawei Technologies
January 2013
<span class="h1">Specifying Civic Address Extensions in</span>
<span class="h1">the Presence Information Data Format Location Object (PIDF-LO)</span>
Abstract
New fields are occasionally added to civic addresses. A backward-
compatible mechanism for adding civic address elements to the Geopriv
civic address format is described. A formal mechanism for handling
unsupported extensions when translating between XML and DHCP civic
address forms is defined for entities that need to perform this
translation. Initial extensions for some new elements are also
defined. The Location-to-Service Translation (LoST) protocol
mechanism (defined in <a href="./rfc5222">RFC 5222</a>) that returns civic address element
names used for validation of location information is clarified and is
normatively updated to require a qualifying namespace identifier on
each civic address element returned as part of the validation
process.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in <a href="./rfc5741#section-2">Section 2 of RFC 5741</a>.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
<a href="https://www.rfc-editor.org/info/rfc6848">http://www.rfc-editor.org/info/rfc6848</a>.
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Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) 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
<a href="#section-1">1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a>
<a href="#section-1.1">1.1</a>. Motivating Example . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-1.2">1.2</a>. Terminology . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-2">2</a>. Specifying Civic Address Extensions . . . . . . . . . . . . . <a href="#page-5">5</a>
<a href="#section-3">3</a>. Translating Unsupported Elements . . . . . . . . . . . . . . . <a href="#page-6">6</a>
<a href="#section-3.1">3.1</a>. XML to DHCP Format Translation . . . . . . . . . . . . . . <a href="#page-6">6</a>
<a href="#section-3.2">3.2</a>. Extension Civic Address Type (CAtype) . . . . . . . . . . <a href="#page-6">6</a>
<a href="#section-3.3">3.3</a>. DHCP to XML Format Translation . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-3.4">3.4</a>. Conversion Example . . . . . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-4">4</a>. CAtypes Registry . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-5">5</a>. Civic Extensions . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-5.1">5.1</a>. Pole Number . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-5.2">5.2</a>. Milepost . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-10">10</a>
<a href="#section-5.3">5.3</a>. Street Type Prefix . . . . . . . . . . . . . . . . . . . . <a href="#page-10">10</a>
<a href="#section-5.4">5.4</a>. House Number Prefix . . . . . . . . . . . . . . . . . . . <a href="#page-10">10</a>
<a href="#section-5.5">5.5</a>. XML Extension Schema . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-5.6">5.6</a>. Extension Examples . . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6">6</a>. Using Local Civic Extension with the LoST Protocol . . . . . . <a href="#page-12">12</a>
<a href="#section-7">7</a>. Security Considerations . . . . . . . . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-8">8</a>. IANA Considerations . . . . . . . . . . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-8.1">8.1</a>. CAtype Registration for Extensions . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-8.2">8.2</a>. Changes to the CAtype Registry . . . . . . . . . . . . . . <a href="#page-14">14</a>
<a href="#section-8.3">8.3</a>. Registration Template . . . . . . . . . . . . . . . . . . <a href="#page-14">14</a>
<a href="#section-8.4">8.4</a>. Registration of the CAtypes Defined in this Document . . . <a href="#page-15">15</a>
<a href="#section-8.5">8.5</a>. Registration Policy and Expert Guidance . . . . . . . . . <a href="#page-16">16</a>
<a href="#section-8.6">8.6</a>. URN Sub-Namespace Registration . . . . . . . . . . . . . . <a href="#page-17">17</a>
<a href="#section-8.7">8.7</a>. XML Schema Registration . . . . . . . . . . . . . . . . . <a href="#page-17">17</a>
<a href="#section-9">9</a>. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-17">17</a>
<a href="#section-10">10</a>. References . . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-18">18</a>
<a href="#section-10.1">10.1</a>. Normative References . . . . . . . . . . . . . . . . . . . <a href="#page-18">18</a>
<a href="#section-10.2">10.2</a>. Informative References . . . . . . . . . . . . . . . . . . <a href="#page-19">19</a>
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<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
The Geopriv civic location specifications ([<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>], [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>])
define an XML and binary representations for civic addresses that
allow for the expression of civic addresses. Guidance for the use of
these formats for the civic addresses in different countries is
included in [<a href="./rfc5774" title=""Considerations for Civic Addresses in the Presence Information Data Format Location Object (PIDF-LO): Guidelines and IANA Registry Definition"">RFC5774</a>].
Subsequent to these specifications being produced, use cases for
extending the civic address format with new elements have emerged.
[<a href="./rfc5774" title=""Considerations for Civic Addresses in the Presence Information Data Format Location Object (PIDF-LO): Guidelines and IANA Registry Definition"">RFC5774</a>] describes a mechanism for mapping long-standing address
formats into the civic address elements defined in [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>] and
[<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>]. However, some of these existing address elements do not
readily fit into the civic address elements defined in [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>] and
[<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>]. In these cases, creating new civic address elements
provides a better solution than overloading existing civic address
fields, which may cause confusion.
The XML format for civic addresses [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>] provides a mechanism
that allows for the addition of standardized or privately understood
elements. A similar facility for private extension is not provided
for the DHCP format [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>], though new specifications are able to
define new CAtypes (civic address types).
A recipient of a civic address in either format currently has no
option other than to ignore elements that it does not understand.
This results in any elements that are unknown to that recipient being
discarded if a recipient performs a translation between the two
formats. In order for a new extension to be preserved through
translation by any recipient, the recipient has to understand the
extension and know how to correlate an XML element with a CAtype.
This document describes how new civic address elements are added.
Extensions always start with the definition of XML elements. A
mechanism for carrying the extension in the DHCP format is described.
A new XML namespace containing a small number of additional civic
elements is also defined and can be used as a template to illustrate
how other extensions can be defined as required.
These mechanisms ensure that any translation between formats can be
performed consistently and without loss of information. Translation
between formats can occur without knowledge of every extension that
is present.
The registry of numeric CAtypes is modified so that the creators of
extensions can advertise new namespaces and civic elements to
encourage maximum reuse.
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The additions described in this document are backwardly compatible.
Existing implementations may cause extension information to be lost,
but the presence of extensions does not affect an implementation that
conforms to either [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>] or [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>].
This document also normatively updates [<a href="./rfc5222" title=""LoST: A Location-to-Service Translation Protocol"">RFC5222</a>] to clarify that the
namespace must be included with the element name in the lists of
valid, invalid, and not checked elements in the <locationValidation>
part of a Location-to-Service Translation (LoST) response. While the
LoST schema does not need to be changed, the example in the document
is updated to show the namespaces in the lists.
<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a>. Motivating Example</span>
One instance where translation might be necessary is where a device
receives location configuration using DHCP [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>]. Conversion of
DHCP information to an XML form is necessary if the device wishes to
use the DHCP-provided information in a range of applications,
including location-based presence services [<a href="./rfc4079" title=""A Presence Architecture for the Distribution of GEOPRIV Location Objects"">RFC4079</a>] and emergency
calling [<a href="./rfc5012" title=""Requirements for Emergency Context Resolution with Internet Technologies"">RFC5012</a>].
+--------+ +--------+ +-----------+
| DHCP | DHCP | Device | XML | Recipient | e.g., Presence
| Server |--------->| |-------->| | Agent
+--------+ +--------+ +-----------+
Figure 1: Conversion Scenario
The device that performs the translation between the DHCP and XML
formats might not be aware of some of the extensions that are in use.
Without knowledge of these extensions and how they are represented in
XML, the device is forced to discard them.
These extensions could be useful, or may be critical, to the ultimate
consumers of this information. For instance, an extension element
might provide a presence watcher with important information in
locating the device, or an extension might be significant in choosing
a particular call route.
<span class="h3"><a class="selflink" id="section-1.2" href="#section-1.2">1.2</a>. Terminology</span>
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 [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>].
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<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Specifying Civic Address Extensions</span>
The civic schema in [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>] defines an ordered structure of
elements that can be combined to describe a civic address. The XML
extension point at the end of this sequence is used to extend the
address.
New elements are defined in a new XML namespace [<a href="#ref-XMLNS" title=""Namespaces in XML 1.1 (Second Edition)"">XMLNS</a>]. This is
true of address elements with significance within private or
localized domains as well as those that are intended for global
applicability.
New elements SHOULD use the basic "caType" schema type defined in
[<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>]. This type provides an optional "xml:lang" attribute.
For example, suppose the (fictitious) Central Devon Canals Authority
wishes to introduce a new civic element called "bridge". The
authority defines an XML namespace that includes a "bridge" element.
The namespace needs to be a unique URI, for example
"<a href="http://devon.canals.example.com/civic">http://devon.canals.example.com/civic</a>".
A civic address that includes the new "bridge" element is shown in
Figure 2.
<civicAddress xml:lang="en-GB"
xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:cdc="http://devon.canals.example.com/civic">
<country>UK</country>
<A1>Devon</A1>
<A3>Monkokehampton</A3>
<RD>Deckport</RD>
<STS>Cross</STS>
<cdc:bridge>21451338</cdc:bridge>
</civicAddress>
Figure 2: Extended Civic Address Example
An entity that receives this location information might not
understand the extension address element. As long as the added
element is able to be safely ignored, the remainder of the civic
address can be used. The result is that the information is not as
useful as it could be, but the added element does not prevent the use
of the remainder of the address.
The address can be passed to other applications, such as a LoST
server [<a href="./rfc5222" title=""LoST: A Location-to-Service Translation Protocol"">RFC5222</a>], without modification. If the application
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understands the added element(s), it is able to make use of that
information. For example, if this civic address is acquired using
HTTP-Enabled Location Delivery (HELD) [<a href="./rfc5985" title=""HTTP-Enabled Location Delivery (HELD)"">RFC5985</a>], it can be included
in a LoST request directly.
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Translating Unsupported Elements</span>
Unsupported civic address elements can be carried without consequence
as long as the format of the address does not change. However,
conversion between formats has been shown to be necessary.
Format conversion requires knowledge of the format of the address
elements. An entity performing a conversion between XML and DHCP
address formats is forced to discard unrecognized elements. The
entity performing the conversion has no way to know the correct
element to use in the target format.
This document defines a single extension element for the DHCP format
that makes knowledge of extensions unnecessary during conversion.
This extension element relies on the extension mechanisms defined for
the XML format. New extensions to the civic address format MUST be
defined only for the XML format; these extensions are then conveyed
in DHCP using the extension element.
Further extensions to the DHCP format are prohibited; these
extensions cannot be safely conveyed in environments where conversion
is possible.
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. XML to DHCP Format Translation</span>
Extensions to the XML format [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>] are defined in a new XML
namespace [<a href="#ref-XMLNS" title=""Namespaces in XML 1.1 (Second Edition)"">XMLNS</a>]. The XML namespace received in DHCP is expressed
as a URL, however, it should not be dereferenced or treated as a
source location for the actual schema and doing so will serve no
useful purpose.
Extensions in the XML format can be added to a DHCP format civic
address using an extension CAtype.
<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. Extension Civic Address Type (CAtype)</span>
The extension CAtype (CAtype code 40) includes three values that
uniquely identify the XML extension and its value: a namespace URI,
the local name of the XML element, and the text content of that
element. These three values are all included in the value of the
CAtype, each separated by a single whitespace character.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CAtype (40) | Length | Namespace URI ... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Namespace URI (continued) .
. ... .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Space (U+20) | XML element local name .
+---------------+ .
. ... .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Space (U+20) | Extension type value .
+---------------+ .
. ... .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: XML Civic Address Extension CAtype
CAtype (40) identifies the extension CAtype.
Length is the number of octets used to represent the namespace URI,
local name, and value. The length includes the space between the
namespace URI and local name and the space between the local name and
value fields.
The content of a CAtype (after the CAtype code and length) is UTF-8
encoded Unicode text [<a href="./rfc3629" title=""UTF-8, a transformation format of ISO 10646"">RFC3629</a>]. A maximum of 255 octets is allowed.
Octets consumed by the namespace URI and local name reduce the space
available for values.
This conversion only works for elements that have textual content and
an optional "xml:lang" attribute. Elements with complex content or
other attributes -- aside from namespace bindings -- MUST be ignored
if they are not understood.
<span class="h3"><a class="selflink" id="section-3.3" href="#section-3.3">3.3</a>. DHCP to XML Format Translation</span>
The registration of a new CAtype following the process in [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>]
means that a recipient that does not know the equivalent XML is
unable to produce a complete XML representation of the DHCP civic
address. For this reason, this document ends the registration of new
numeric CAtypes. No new registrations of numeric CAtypes can be
made.
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In lieu of making new numerical CAtype assignments, this document
creates a new extensionCA type that is defined in a manner that lets
new civic elements be described in DHCP form by carrying the
namespace and type name of the extension in parameters of the
extensionCA type.
When converting to XML, the namespace prefix used for the extension
element is selected by the entity that performs the conversion.
<span class="h3"><a class="selflink" id="section-3.4" href="#section-3.4">3.4</a>. Conversion Example</span>
The following example civic address contains two extensions:
<civicAddress xml:lang="en-US"
xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:post="http://postsoftheworld.example.com/ns"
xmlns:ap="http://example.com/airport/5.0">
<country>US</country>
<A1>CA</A1>
<post:lamp>2471</post:lamp>
<post:pylon>AQ-374-4(c)</post:pylon>
<ap:airport>LAX</ap:airport>
<ap:terminal>Tom Bradley</ap:terminal>
<ap:concourse>G</ap:concourse>
<ap:gate>36B</ap:gate>
</civicAddress>
Figure 4: XML Example with Multiple Extensions
This is converted to a DHCP form as follows:
country = US
CAtype[0] = en-US
CAtype[1] = CA
CAtype[40] = http://postsoftheworld.example.com/ns lamp 2471
CAtype[40] = http://postsoftheworld.example.com/ns pylon AQ-374-4(c)
CAtype[40] = http://example.com/airport/5.0 airport LAX
CAtype[40] = http://example.com/airport/5.0 terminal Tom Bradley
CAtype[40] = http://example.com/airport/5.0 concourse G
CAtype[40] = http://example.com/airport/5.0 gate 36B
Figure 5: Converted DHCP Example with Multiple Extensions
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<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. CAtypes Registry</span>
[<a id="ref-RFC4776">RFC4776</a>] created the CAtype registry. Among other things, this
registry advertised available civic elements. While it has always
been possible to use an extension namespace to define civic elements
that are not in the CAtype registry, and this document does not
change that, the registry is valuable to alert implementors of
commonly used civic elements and provides guidance to clients of what
elements they should support.
This document alters the CAtype registry in several ways. It closes
the registry to new numeric CAtypes. It deletes the "NENA" column,
which is not needed. It adds columns for a namespace and contact,
and changes the name of the column currently called "PIDF" to "Local
Name". It also adds a column to the registry called "Type". "Type"
can have one of two values "A" and "B". Type A elements are intended
for wide use with many applications and SHOULD be implemented by all
clients unless the client is certain the element will not be
encountered. Type B civic elements MAY be implemented by any client.
Type A civic elements require IETF review, while Type B elements only
require an expert review.
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Civic Extensions</span>
We use this new extension method to define some additional civic
address elements that are needed to correctly encode civic locations
in several countries. The definition of these new civic address
elements also serves as an example of how to define additional
elements using the mechanisms described in this document.
<span class="h3"><a class="selflink" id="section-5.1" href="#section-5.1">5.1</a>. Pole Number</span>
In some areas, utility and lamp posts carry a unique identifier,
which we call a pole number in this document. In some countries, the
label on the lamp post also carries the local emergency service
number, such as "110", encouraging callers to use the pole number to
identify their location.
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_.-----,===.
| | (''''')
| | `---'
| |
| | ,---------,
| | ,---, |Emergency|
| | /|,-.|----->| Number |
| | / |110| '---------'
| | / |`-'|
|_|/ | 2 | ,---------,
| | | 1 | |Lamp Post|
| | | 2 |----->| Number |
|-| | 1 | '---------'
| |\ | 0 |
| | \ | 1 |
| | \ | 4 |
| | \|,,,|
_ | |
``-..|.|
``--.._
`'--.._
Figure 6: Lamp Post with Emergency Number
<span class="h3"><a class="selflink" id="section-5.2" href="#section-5.2">5.2</a>. Milepost</span>
On some roads, trails, railroad rights of way, and other linear
features, a post with a mile or kilometer distance from one end of
the feature may be found (a "milepost"). There are other cases of
poles or markers with numeric indications that are not the same as a
"house number" or street address number.
<span class="h3"><a class="selflink" id="section-5.3" href="#section-5.3">5.3</a>. Street Type Prefix</span>
The civic schema defined in [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>] allows the definition of
address "123 Colorado Boulevard", but it does not allow for the easy
expression of "123 Boulevard Colorado". Adding a street type prefix,
allows a street named in this manner to be more easily represented.
<span class="h3"><a class="selflink" id="section-5.4" href="#section-5.4">5.4</a>. House Number Prefix</span>
The civic schema defined in [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>] provides a house number suffix
element, allowing one to express an address like "123A Main Street",
but it does not contain a corresponding house number prefix. The
house number prefix element allows the expression of address such as
"Z123 Main Street".
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<span class="h3"><a class="selflink" id="section-5.5" href="#section-5.5">5.5</a>. XML Extension Schema</span>
<?xml version="1.0"?>
<xs:schema
targetNamespace="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext"
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:cae="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext"
xmlns:xml="http://www.w3.org/XML/1998/namespace"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:import namespace="urn:ietf:params:xml:pidf:geopriv10:civicAddr"/>
<!-- Post Number -->
<xs:element name="PN" type="ca:caType"/>
<!-- Milepost -->
<xs:element name="MP" type="ca:caType"/>
<!-- Street Type Prefix -->
<xs:element name="STP" type="ca:caType"/>
<!-- House Number Prefix -->
<xs:element name="HNP" type="ca:caType"/>
</xs:schema>
<span class="h3"><a class="selflink" id="section-5.6" href="#section-5.6">5.6</a>. Extension Examples</span>
<civicAddress xml:lang="en-US"
xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:cae="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext">
<country>US</country>
<A1>CA</A1>
<A2>Sacramento</A2>
<RD>I5</RD>
<cae:MP>248</cae:MP>
<cae:PN>22-109-689</cae:PN>
</civicAddress>
Figure 7: XML Example with Post Number and Milepost
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<civicAddress xml:lang="en-US"
xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:cae="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext">
<country>US</country>
<A1>CA</A1>
<A2>Sacramento</A2>
<RD>Colorado</RD>
<HNO>223</HNO>
<cae:STP>Boulevard</cae:STP>
<cae:HNP>A</cae:HNP>
</civicAddress>
Figure 8: XML Example with Street Type Prefix and House Number Prefix
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Using Local Civic Extension with the LoST Protocol</span>
One critical use of civic location information is in next generation
emergency services applications, in particular, call routing
applications. In such cases, location information is provided to a
location-based routing service using the LoST protocol [<a href="./rfc5222" title=""LoST: A Location-to-Service Translation Protocol"">RFC5222</a>].
LoST is used to provide call routing information, but it is also used
to validate location information to ensure that it can route to an
emergency center when required.
LoST is an XML-based protocol, and so the namespace extension
mechanisms described in this document do not impact LoST. When LoST
is used for validation, a <locationValidation> element is returned
containing a list of valid, a list of invalid, and a list of
unchecked civic elements. Figure 9 is an extract of the validation
response in Figure 6 from [<a href="./rfc5222" title=""LoST: A Location-to-Service Translation Protocol"">RFC5222</a>].
<locationValidation>
<valid>country A1 A3 A6</valid>
<invalid>PC</invalid>
<unchecked>HNO</unchecked>
</locationValidation>
Figure 9: Location Validation Example from LoST (<a href="./rfc5222">RFC5222</a>)
The RelaxNG schema in [<a href="./rfc5222" title=""LoST: A Location-to-Service Translation Protocol"">RFC5222</a>] requires the elements in each of
these lists to be namespace qualified, which makes the example in
Figure 6 of [<a href="./rfc5222" title=""LoST: A Location-to-Service Translation Protocol"">RFC5222</a>] erroneous. This issue is especially
significant when local-civic extensions are used as the domain to
which the extensions are attributed may impact their interpretation
by the server or client. To ensure that local-civic extensions do
not cause issues with the LoST server and client implementations, all
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elements listed in a <valid>, <invalid>, or <unchecked> element MUST
be qualified with a namespace. To illustrate this, the extract above
from Figure 6 in [<a href="./rfc5222" title=""LoST: A Location-to-Service Translation Protocol"">RFC5222</a>] becomes Figure 10.
<locationValidation
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
<valid>ca:country ca:A1 ca:A3 ca:A6</valid>
<invalid>ca:PC</invalid>
<unchecked>ca:HNO</unchecked>
</locationValidation>
Figure 10: Corrected Location Validation Example
If a validation request has also included the extensions defined in
<a href="#section-5">Section 5</a>, then the validation response would look like Figure 11.
<locationValidation
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:cae="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext">
<valid>ca:country ca:A1 ca:A3 ca:A6 cae:PN cae:STP</valid>
<invalid>ca:PC</invalid>
<unchecked>ca:HNO cae:MP cae:HNP</unchecked>
</locationValidation>
Figure 11: Corrected Location Validation Example
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. Security Considerations</span>
This document defines a formal way to extend the existing Geopriv
civic address schema. While no security threats are directly
introduced by this document, creators of new civic address extensions
should refer to Sections <a href="#section-4.3.1">4.3.1</a> and <a href="#section-5.1">5.1</a> of [<a href="./rfc3694" title=""Threat Analysis of the Geopriv Protocol"">RFC3694</a>] to understand the
environments in which these new elements will be used. New elements
should only be registered if the person or organization performing
the registration understands any associated risks.
Security threats applicable to the civic address formats are
described in [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>] DHCP and [<a href="./rfc5139" title=""Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)"">RFC5139</a>] XML.
<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. IANA Considerations</span>
This document alters the "CAtypes" registry in the Civic Address
Types Registry established by [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>].
<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>. CAtype Registration for Extensions</span>
IANA has allocated a CAtype code of 40 for the extension CAtype.
Registrations using this code will be made below, in <a href="#section-8.4">Section 8.4</a>.
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<span class="h3"><a class="selflink" id="section-8.2" href="#section-8.2">8.2</a>. Changes to the CAtype Registry</span>
IANA has made the following changes to the CAtype registry:
o No registrations of new CAtype numbers in the Civic Address Types
Registry are permitted, except by IESG Approval [<a href="./rfc5226" title="">RFC5226</a>] under
unusual circumstances.
o The following note has been placed in the header of the CAtypes
registry, above the table:
Note: As specified in <a href="./rfc6848">RFC 6848</a>, new registrations are only
accepted for CAtype 40, using the template specified in
<a href="#section-8.3">Section 8.3</a>.
o The registration procedures are changed: IETF Review (if Type=A),
Expert Review (if Type=B). The designated expert is unchanged.
o The reference for the table is changed: [<a href="./rfc4776" title=""Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information"">RFC4776</a>], <a href="./rfc6848">RFC 6848</a>
o The column called "NENA" is removed.
o The column called "PIDF" is renamed to "Local Name".
o New columns are added named "Namespace URI", "Contact", "Schema"
and "Type". All existing entries will have the following values
for those new columns:
Namespace URI: urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr
Contact: The IESG ([email protected]); the GEOPRIV working group
([email protected])
Schema: urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr
Type: A
<span class="h3"><a class="selflink" id="section-8.3" href="#section-8.3">8.3</a>. Registration Template</span>
New registrations in the Civic Address Types Registry require the
following information:
CAtype: The assigned numeric CAtype. All new registrations will use
the value 40.
Namespace URI: A unique identifier for the XML namespace used for
the extension element.
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Local Name: The local name of an XML element that carries the civic
address element.
Description: A brief description of the semantics of the civic
address element.
Example (optional): One or more simple examples of the element.
Contact: Contact details for the person providing the extension.
Specification (optional): A reference to a specification for the
civic address element.
Schema (optional): A reference to a formal schema (XML schema,
RelaxNG, or other form) that defines the extension.
Type: "A" or "B".
If Type is "A", all clients SHOULD implement this element. If
Type is "B", clients MAY implement this element.
<span class="h3"><a class="selflink" id="section-8.4" href="#section-8.4">8.4</a>. Registration of the CAtypes Defined in this Document</span>
This section registers the following four new CAtypes in the Civic
Address Types Registry.
Post Number (see <a href="#section-5.1">Section 5.1</a>):
CAtype: 40
Namespace URI: urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
Local Name: PN
Description: Post number that is attributed to a lamp post or
utility pole.
Contact: The IESG ([email protected]); the GEOPRIV working group
([email protected])
Specification: <a href="./rfc6848#section-5">RFC 6848, Section 5</a>
Schema: urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
Type: A
Milepost (see <a href="#section-5.2">Section 5.2</a>):
CAtype: 40
Namespace URI: urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
Local Name: MP
Description: Milepost: a marker indicating distance to or from a
place (often a town).
Contact: The IESG ([email protected]); the GEOPRIV working group
([email protected])
Specification: <a href="./rfc6848#section-5">RFC 6848, Section 5</a>
Schema: urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
Type: A
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Street Type Prefix (see <a href="#section-5.3">Section 5.3</a>):
CAtype: 40
Namespace URI: urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
Local Name: STP
Description: Street Type Prefix.
Contact: The IESG ([email protected]); the GEOPRIV working group
([email protected])
Specification: <a href="./rfc6848#section-5">RFC 6848, Section 5</a>
Schema: urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
Type: A
House Number Prefix (see <a href="#section-5.4">Section 5.4</a>):
CAtype: 40
Namespace URI: urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
Local Name: HNP
Description: House Number Prefix.
Contact: The IESG ([email protected]); the GEOPRIV working group
([email protected])
Specification: <a href="./rfc6848#section-5">RFC 6848, Section 5</a>
Schema: urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
Type: A
<span class="h3"><a class="selflink" id="section-8.5" href="#section-8.5">8.5</a>. Registration Policy and Expert Guidance</span>
The "CAtypes" registry is altered to operate on a registration policy
of "Expert Review", and optionally "Specification Required" [<a href="./rfc5226" title="">RFC5226</a>]
if the element being registered has a Type value of "B".
The registration rules for "Specification Required" are followed only
if a registration includes a reference to a specification.
Registrations can be made without a specification reference.
If the element being registered has a Type value of "A", then the
registration policy is "IETF Review" [<a href="./rfc5226" title="">RFC5226</a>].
All registrations are reviewed to identify potential duplication
between registered elements. Duplicated semantics are not prohibited
in the registry, though it is preferred if existing elements are
used. The expert review is advised to recommend the use of existing
elements following the guidance in [<a href="./rfc5774" title=""Considerations for Civic Addresses in the Presence Information Data Format Location Object (PIDF-LO): Guidelines and IANA Registry Definition"">RFC5774</a>]. Any registration that
is a duplicate or could be considered a close match for the semantics
of an existing element SHOULD include a discussion of the reasons
that the existing element was not reused.
[<a id="ref-RFC6280">RFC6280</a>] provides a comprehensive framework concerning the privacy
of location information as pertaining to its use in Internet
applications. The expert reviewer is asked to keep the spirit of
this document in mind when reviewing new CAtype registrations.
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<span class="h3"><a class="selflink" id="section-8.6" href="#section-8.6">8.6</a>. URN Sub-Namespace Registration</span>
IANA has registered a new XML namespace, as per the guidelines in
[<a href="./rfc3688" title=""The IETF XML Registry"">RFC3688</a>].
URI: urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
Registrant Contact: IETF GEOPRIV working group ([email protected]),
James Winterbottom ([email protected])
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"<a href="http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd</a>">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<title>GEOPRIV Civic Address Extensions</title>
</head>
<body>
<h1>Additional Fields for GEOPRIV Civic Address</h1>
<h2>urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext</h2>
<p>See <a href="http://www.rfc-editor.org/rfc/rfc6848.txt">
<a href="./rfc6848">RFC 6848</a></a>.</p>
</body>
</html>
END
<span class="h3"><a class="selflink" id="section-8.7" href="#section-8.7">8.7</a>. XML Schema Registration</span>
This section registers an XML schema as per the procedures in
[<a href="./rfc3688" title=""The IETF XML Registry"">RFC3688</a>].
URI: urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
Registrant Contact: IETF GEOPRIV working group ([email protected]),
James Winterbottom ([email protected])
XML: The XML for this schema can be found as the entirety of
<a href="#section-5.5">Section 5.5</a> of this document.
<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. Acknowledgements</span>
Thanks to anyone who has tried to extend the civic schema and found
it a little less than intuitive.
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<span class="h2"><a class="selflink" id="section-10" href="#section-10">10</a>. References</span>
<span class="h3"><a class="selflink" id="section-10.1" href="#section-10.1">10.1</a>. Normative References</span>
[<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.
[<a id="ref-RFC3629">RFC3629</a>] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, <a href="./rfc3629">RFC 3629</a>, November 2003.
[<a id="ref-RFC3688">RFC3688</a>] Mealling, M., "The IETF XML Registry", <a href="https://www.rfc-editor.org/bcp/bcp81">BCP 81</a>, <a href="./rfc3688">RFC 3688</a>,
January 2004.
[<a id="ref-RFC3694">RFC3694</a>] Danley, M., Mulligan, D., Morris, J., and J. Peterson,
"Threat Analysis of the Geopriv Protocol", <a href="./rfc3694">RFC 3694</a>,
February 2004.
[<a id="ref-RFC4776">RFC4776</a>] Schulzrinne, H., "Dynamic Host Configuration Protocol
(DHCPv4 and DHCPv6) Option for Civic Addresses
Configuration Information", <a href="./rfc4776">RFC 4776</a>, November 2006.
[<a id="ref-RFC5139">RFC5139</a>] Thomson, M. and J. Winterbottom, "Revised Civic Location
Format for Presence Information Data Format Location
Object (PIDF-LO)", <a href="./rfc5139">RFC 5139</a>, February 2008.
[<a id="ref-RFC5222">RFC5222</a>] Hardie, T., Newton, A., Schulzrinne, H., and H.
Tschofenig, "LoST: A Location-to-Service Translation
Protocol", <a href="./rfc5222">RFC 5222</a>, August 2008.
[<a id="ref-RFC5226">RFC5226</a>] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", <a href="https://www.rfc-editor.org/bcp/bcp26">BCP 26</a>, <a href="./rfc5226">RFC 5226</a>,
May 2008.
[<a id="ref-RFC6280">RFC6280</a>] Barnes, R., Lepinski, M., Cooper, A., Morris, J.,
Tschofenig, H., and H. Schulzrinne, "An Architecture for
Location and Location Privacy in Internet Applications",
<a href="https://www.rfc-editor.org/bcp/bcp160">BCP 160</a>, <a href="./rfc6280">RFC 6280</a>, July 2011.
[<a id="ref-XMLNS">XMLNS</a>] Hollander, D., Layman, A., Tobin, R., and T. Bray,
"Namespaces in XML 1.1 (Second Edition)", World Wide Web
Consortium Recommendation REC-xml-names11-20060816,
August 2006,
<<a href="http://www.w3.org/TR/2006/REC-xml-names11-20060816">http://www.w3.org/TR/2006/REC-xml-names11-20060816</a>>.
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<span class="h3"><a class="selflink" id="section-10.2" href="#section-10.2">10.2</a>. Informative References</span>
[<a id="ref-RFC4079">RFC4079</a>] Peterson, J., "A Presence Architecture for the
Distribution of GEOPRIV Location Objects", <a href="./rfc4079">RFC 4079</a>,
July 2005.
[<a id="ref-RFC5012">RFC5012</a>] Schulzrinne, H. and R. Marshall, "Requirements for
Emergency Context Resolution with Internet Technologies",
<a href="./rfc5012">RFC 5012</a>, January 2008.
[<a id="ref-RFC5774">RFC5774</a>] Wolf, K. and A. Mayrhofer, "Considerations for Civic
Addresses in the Presence Information Data Format Location
Object (PIDF-LO): Guidelines and IANA Registry
Definition", <a href="https://www.rfc-editor.org/bcp/bcp154">BCP 154</a>, <a href="./rfc5774">RFC 5774</a>, March 2010.
[<a id="ref-RFC5985">RFC5985</a>] Barnes, M., "HTTP-Enabled Location Delivery (HELD)",
<a href="./rfc5985">RFC 5985</a>, September 2010.
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Authors' Addresses
James Winterbottom
CommScope
Suit 1, Level 2
iC Enterprise 1, Innovation Campus
Squires Way
North Wollongong, NSW 2500
AU
Phone: +61 242 212938
EMail: [email protected]
Martin Thomson
Skype
3210 Porter Drive
Palo Alto, CA 94304
US
EMail: [email protected]
Richard Barnes
BBN Technologies
9861 Broken Land Parkway
Columbia, MD 21046
US
Phone: +1 410 290 6169
EMail: [email protected]
Brian Rosen
NeuStar, Inc.
470 Conrad Dr
Mars, PA 16046
US
EMail: [email protected]
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Robins George
Huawei Technologies
Huawei Base, Bantian, Longgan District
Shenzhen, Guangdong 518129
P. R. China
Phone: +86 755 2878 8314
EMail: [email protected]
Winterbottom, et al. Standards Track [Page 21]
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