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rfc:rfc6848

Internet Engineering Task Force (IETF) J. Winterbottom Request for Comments: 6848 CommScope Updates: 4776, 5222 M. Thomson Category: Standards Track Skype ISSN: 2070-1721 R. Barnes

                                                      BBN Technologies
                                                              B. Rosen
                                                         NeuStar, Inc.
                                                             R. George
                                                   Huawei Technologies
                                                          January 2013
               Specifying Civic Address Extensions in
   the Presence Information Data Format Location Object (PIDF-LO)

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.

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 Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6848.

Winterbottom, et al. Standards Track [Page 1] RFC 6848 Civic Extensions January 2013

Copyright Notice

 Copyright (c) 2013 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
 (http://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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.1.  Motivating Example . . . . . . . . . . . . . . . . . . . .  4
   1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
 2.  Specifying Civic Address Extensions  . . . . . . . . . . . . .  5
 3.  Translating Unsupported Elements . . . . . . . . . . . . . . .  6
   3.1.  XML to DHCP Format Translation . . . . . . . . . . . . . .  6
   3.2.  Extension Civic Address Type (CAtype)  . . . . . . . . . .  6
   3.3.  DHCP to XML Format Translation . . . . . . . . . . . . . .  7
   3.4.  Conversion Example . . . . . . . . . . . . . . . . . . . .  8
 4.  CAtypes Registry . . . . . . . . . . . . . . . . . . . . . . .  9
 5.  Civic Extensions . . . . . . . . . . . . . . . . . . . . . . .  9
   5.1.  Pole Number  . . . . . . . . . . . . . . . . . . . . . . .  9
   5.2.  Milepost . . . . . . . . . . . . . . . . . . . . . . . . . 10
   5.3.  Street Type Prefix . . . . . . . . . . . . . . . . . . . . 10
   5.4.  House Number Prefix  . . . . . . . . . . . . . . . . . . . 10
   5.5.  XML Extension Schema . . . . . . . . . . . . . . . . . . . 11
   5.6.  Extension Examples . . . . . . . . . . . . . . . . . . . . 11
 6.  Using Local Civic Extension with the LoST Protocol . . . . . . 12
 7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
 8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   8.1.  CAtype Registration for Extensions . . . . . . . . . . . . 13
   8.2.  Changes to the CAtype Registry . . . . . . . . . . . . . . 14
   8.3.  Registration Template  . . . . . . . . . . . . . . . . . . 14
   8.4.  Registration of the CAtypes Defined in this Document . . . 15
   8.5.  Registration Policy and Expert Guidance  . . . . . . . . . 16
   8.6.  URN Sub-Namespace Registration . . . . . . . . . . . . . . 17
   8.7.  XML Schema Registration  . . . . . . . . . . . . . . . . . 17
 9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
   10.1. Normative References . . . . . . . . . . . . . . . . . . . 18
   10.2. Informative References . . . . . . . . . . . . . . . . . . 19

Winterbottom, et al. Standards Track [Page 2] RFC 6848 Civic Extensions January 2013

1. Introduction

 The Geopriv civic location specifications ([RFC4776], [RFC5139])
 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 [RFC5774].
 Subsequent to these specifications being produced, use cases for
 extending the civic address format with new elements have emerged.
 [RFC5774] describes a mechanism for mapping long-standing address
 formats into the civic address elements defined in [RFC4776] and
 [RFC5139].  However, some of these existing address elements do not
 readily fit into the civic address elements defined in [RFC4776] and
 [RFC5139].  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 [RFC5139] 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 [RFC4776], 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.

Winterbottom, et al. Standards Track [Page 3] RFC 6848 Civic Extensions January 2013

 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 [RFC4776] or [RFC5139].
 This document also normatively updates [RFC5222] 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.

1.1. Motivating Example

 One instance where translation might be necessary is where a device
 receives location configuration using DHCP [RFC4776].  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 [RFC4079] and emergency
 calling [RFC5012].
  +--------+          +--------+         +-----------+
  | 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.

1.2. Terminology

 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].

Winterbottom, et al. Standards Track [Page 4] RFC 6848 Civic Extensions January 2013

2. Specifying Civic Address Extensions

 The civic schema in [RFC5139] 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 [XMLNS].  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
 [RFC5139].  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
 "http://devon.canals.example.com/civic".
 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 [RFC5222], without modification.  If the application

Winterbottom, et al. Standards Track [Page 5] RFC 6848 Civic Extensions January 2013

 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) [RFC5985], it can be included
 in a LoST request directly.

3. Translating Unsupported Elements

 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.

3.1. XML to DHCP Format Translation

 Extensions to the XML format [RFC5139] are defined in a new XML
 namespace [XMLNS].  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.

3.2. Extension Civic Address Type (CAtype)

 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.

Winterbottom, et al. Standards Track [Page 6] RFC 6848 Civic Extensions January 2013

  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 [RFC3629].  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.

3.3. DHCP to XML Format Translation

 The registration of a new CAtype following the process in [RFC4776]
 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.

Winterbottom, et al. Standards Track [Page 7] RFC 6848 Civic Extensions January 2013

 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.

3.4. Conversion Example

 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

Winterbottom, et al. Standards Track [Page 8] RFC 6848 Civic Extensions January 2013

4. CAtypes Registry

 [RFC4776] 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.

5. Civic Extensions

 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.

5.1. Pole Number

 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.

Winterbottom, et al. Standards Track [Page 9] RFC 6848 Civic Extensions January 2013

                           _.-----,===.
                          | |    (''''')
                          | |     `---'
                          | |
                          | |               ,---------,
                          | |    ,---,      |Emergency|
                          | |   /|,-.|----->| Number  |
                          | |  / |110|      '---------'
                          | | /  |`-'|
                          |_|/   | 2 |      ,---------,
                          | |    | 1 |      |Lamp Post|
                          | |    | 2 |----->| Number  |
                          |-|    | 1 |      '---------'
                          | |\   | 0 |
                          | | \  | 1 |
                          | |  \ | 4 |
                          | |   \|,,,|
                    _     | |
                     ``-..|.|
                            ``--.._
                                   `'--.._
               Figure 6: Lamp Post with Emergency Number

5.2. Milepost

 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.

5.3. Street Type Prefix

 The civic schema defined in [RFC5139] 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.

5.4. House Number Prefix

 The civic schema defined in [RFC5139] 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".

Winterbottom, et al. Standards Track [Page 10] RFC 6848 Civic Extensions January 2013

5.5. XML Extension Schema

<?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>

5.6. Extension Examples

 <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

Winterbottom, et al. Standards Track [Page 11] RFC 6848 Civic Extensions January 2013

 <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

6. Using Local Civic Extension with the LoST Protocol

 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 [RFC5222].
 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 [RFC5222].
 <locationValidation>
     <valid>country A1 A3 A6</valid>
     <invalid>PC</invalid>
     <unchecked>HNO</unchecked>
 </locationValidation>
       Figure 9: Location Validation Example from LoST (RFC5222)
 The RelaxNG schema in [RFC5222] requires the elements in each of
 these lists to be namespace qualified, which makes the example in
 Figure 6 of [RFC5222] 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

Winterbottom, et al. Standards Track [Page 12] RFC 6848 Civic Extensions January 2013

 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 [RFC5222] 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
 Section 5, 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

7. Security Considerations

 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 4.3.1 and 5.1 of [RFC3694] 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 [RFC4776] DHCP and [RFC5139] XML.

8. IANA Considerations

 This document alters the "CAtypes" registry in the Civic Address
 Types Registry established by [RFC4776].

8.1. CAtype Registration for Extensions

 IANA has allocated a CAtype code of 40 for the extension CAtype.
 Registrations using this code will be made below, in Section 8.4.

Winterbottom, et al. Standards Track [Page 13] RFC 6848 Civic Extensions January 2013

8.2. Changes to the CAtype Registry

 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 [RFC5226] under
    unusual circumstances.
 o  The following note has been placed in the header of the CAtypes
    registry, above the table:
       Note: As specified in RFC 6848, new registrations are only
       accepted for CAtype 40, using the template specified in
       Section 8.3.
 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: [RFC4776], RFC 6848
 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 (iesg@ietf.org); the GEOPRIV working group
       (geopriv@ietf.org)
    Schema:  urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr
    Type:  A

8.3. Registration Template

 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.

Winterbottom, et al. Standards Track [Page 14] RFC 6848 Civic Extensions January 2013

 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.

8.4. Registration of the CAtypes Defined in this Document

 This section registers the following four new CAtypes in the Civic
 Address Types Registry.
 Post Number (see Section 5.1):
 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 (iesg@ietf.org); the GEOPRIV working group
    (geopriv@ietf.org)
 Specification:  RFC 6848, Section 5
 Schema:  urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
 Type:  A
 Milepost (see Section 5.2):
 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 (iesg@ietf.org); the GEOPRIV working group
    (geopriv@ietf.org)
 Specification:  RFC 6848, Section 5
 Schema:  urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
 Type:  A

Winterbottom, et al. Standards Track [Page 15] RFC 6848 Civic Extensions January 2013

 Street Type Prefix (see Section 5.3):
 CAtype:  40
 Namespace URI:  urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
 Local Name:  STP
 Description:  Street Type Prefix.
 Contact:  The IESG (iesg@ietf.org); the GEOPRIV working group
    (geopriv@ietf.org)
 Specification:  RFC 6848, Section 5
 Schema:  urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
 Type:  A
 House Number Prefix (see Section 5.4):
 CAtype:  40
 Namespace URI:  urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
 Local Name:  HNP
 Description:  House Number Prefix.
 Contact:  The IESG (iesg@ietf.org); the GEOPRIV working group
    (geopriv@ietf.org)
 Specification:  RFC 6848, Section 5
 Schema:  urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
 Type:  A

8.5. Registration Policy and Expert Guidance

 The "CAtypes" registry is altered to operate on a registration policy
 of "Expert Review", and optionally "Specification Required" [RFC5226]
 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" [RFC5226].
 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 [RFC5774].  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.
 [RFC6280] 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.

Winterbottom, et al. Standards Track [Page 16] RFC 6848 Civic Extensions January 2013

8.6. URN Sub-Namespace Registration

 IANA has registered a new XML namespace, as per the guidelines in
 [RFC3688].
 URI:  urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr:ext
 Registrant Contact:  IETF GEOPRIV working group (geopriv@ietf.org),
    James Winterbottom (james.Winterbottom@commscope.com)
 XML:
   BEGIN
     <?xml version="1.0"?>
     <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
       "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
     <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">
            RFC 6848</a>.</p>
       </body>
     </html>
   END

8.7. XML Schema Registration

 This section registers an XML schema as per the procedures in
 [RFC3688].
 URI:  urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr:ext
 Registrant Contact:  IETF GEOPRIV working group (geopriv@ietf.org),
    James Winterbottom (james.Winterbottom@commscope.com)
 XML:  The XML for this schema can be found as the entirety of
    Section 5.5 of this document.

9. Acknowledgements

 Thanks to anyone who has tried to extend the civic schema and found
 it a little less than intuitive.

Winterbottom, et al. Standards Track [Page 17] RFC 6848 Civic Extensions January 2013

10. References

10.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, November 2003.
 [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
            January 2004.
 [RFC3694]  Danley, M., Mulligan, D., Morris, J., and J. Peterson,
            "Threat Analysis of the Geopriv Protocol", RFC 3694,
            February 2004.
 [RFC4776]  Schulzrinne, H., "Dynamic Host Configuration Protocol
            (DHCPv4 and DHCPv6) Option for Civic Addresses
            Configuration Information", RFC 4776, November 2006.
 [RFC5139]  Thomson, M. and J. Winterbottom, "Revised Civic Location
            Format for Presence Information Data Format Location
            Object (PIDF-LO)", RFC 5139, February 2008.
 [RFC5222]  Hardie, T., Newton, A., Schulzrinne, H., and H.
            Tschofenig, "LoST: A Location-to-Service Translation
            Protocol", RFC 5222, August 2008.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.
 [RFC6280]  Barnes, R., Lepinski, M., Cooper, A., Morris, J.,
            Tschofenig, H., and H. Schulzrinne, "An Architecture for
            Location and Location Privacy in Internet Applications",
            BCP 160, RFC 6280, July 2011.
 [XMLNS]    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,
            <http://www.w3.org/TR/2006/REC-xml-names11-20060816>.

Winterbottom, et al. Standards Track [Page 18] RFC 6848 Civic Extensions January 2013

10.2. Informative References

 [RFC4079]  Peterson, J., "A Presence Architecture for the
            Distribution of GEOPRIV Location Objects", RFC 4079,
            July 2005.
 [RFC5012]  Schulzrinne, H. and R. Marshall, "Requirements for
            Emergency Context Resolution with Internet Technologies",
            RFC 5012, January 2008.
 [RFC5774]  Wolf, K. and A. Mayrhofer, "Considerations for Civic
            Addresses in the Presence Information Data Format Location
            Object (PIDF-LO): Guidelines and IANA Registry
            Definition", BCP 154, RFC 5774, March 2010.
 [RFC5985]  Barnes, M., "HTTP-Enabled Location Delivery (HELD)",
            RFC 5985, September 2010.

Winterbottom, et al. Standards Track [Page 19] RFC 6848 Civic Extensions January 2013

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: james.winterbottom@commscope.com
 Martin Thomson
 Skype
 3210 Porter Drive
 Palo Alto, CA  94304
 US
 EMail: martin.thomson@gmail.com
 Richard Barnes
 BBN Technologies
 9861 Broken Land Parkway
 Columbia, MD  21046
 US
 Phone: +1 410 290 6169
 EMail: rbarnes@bbn.com
 Brian Rosen
 NeuStar, Inc.
 470 Conrad Dr
 Mars, PA  16046
 US
 EMail: br@brianrosen.net

Winterbottom, et al. Standards Track [Page 20] RFC 6848 Civic Extensions January 2013

 Robins George
 Huawei Technologies
 Huawei Base, Bantian, Longgan District
 Shenzhen, Guangdong  518129
 P. R. China
 Phone: +86 755 2878 8314
 EMail: robinsgv@gmail.com

Winterbottom, et al. Standards Track [Page 21]

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