Device Capability Negotiation for Device-Based Location Determination and Location Measurements in HELD
draft-thomson-geopriv-held-capabilities-05

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Abstract

A framework for the exchange of capabilities in HELD is described. Capabilities for enabling device-based measurements and device-based location generation are defined based on this framework.

Table of Contents

1.  Introduction
2.  Conventions used in this document
3.  Capabilities Exchange Overview
    3.1.  Capabilities Exchange
4.  The Capability Indication
    4.1.  Retrieving Data from the Device
    4.2.  Capability Definitions
5.  The Location Capability
    5.1.  Location Capability Summary
6.  Location Measurement Capability
    6.1.  HELD Measurement Request
    6.2.  Location Measurement Capability Summary
7.  XML Schema
    7.1.  Capabilities Schema
    7.2.  HELD Measurement Request Schema
8.  Security Considerations
9.  IANA Considerations
    9.1.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap
    9.2.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:location
    9.3.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:lm
    9.4.  XML Schema Registration for HELD Capabilities
    9.5.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:mr
    9.6.  XML Schema Registration for HELD Measurement Request and Response
10.  References
    10.1.  Normative References
    10.2.  Informative References

1.  Introduction

A device is a good source of information about its location. Even where a device is unable to independently determine its location, it can often make observations about its environment and network attachment that are of use in determining its position. Making this information available to the Location Information Server (LIS) in the access network can improve the quality of location estimates for the device.

Requests that retrieve location information by value are largely covered by the measurement information and data formats described in [I‑D.thomson‑geopriv‑held‑measurements] (Thomson, M. and J. Winterbottom, “Using Device-provided Location-Related Measurements in Location Configuration Protocols,” October 2009.). However, location information provided through location URIs cannot utilise this information.

This document outlines a method whereby a device indicates capabilities to a LIS during the creation of a HELD context (see [I‑D.winterbottom‑geopriv‑held‑context] (Winterbottom, J., Tschofenig, H., and M. Thomson, “Location URI Contexts in HTTP-Enabled Location Delivery (HELD),” October 2009.)). The LIS is able to then exercise those capabilities to assist it in the generation of location information, or to acquire location information from the device.

2.  Conventions used in this document

This document relies on definitions from a range of specification. Use of the terms LIS and Device is consistent with [I‑D.ietf‑geopriv‑http‑location‑delivery] (Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, “HTTP Enabled Location Delivery (HELD),” August 2009.). Location measurement is defined in [I‑D.thomson‑geopriv‑held‑measurements] (Thomson, M. and J. Winterbottom, “Using Device-provided Location-Related Measurements in Location Configuration Protocols,” October 2009.) and location estimate is defined in [I‑D.thomson‑geopriv‑uncertainty] (Thomson, M. and J. Winterbottom, “Representation of Uncertainty and Confidence in PIDF-LO,” November 2009.). The term context is used as defined in [I‑D.winterbottom‑geopriv‑held‑context] (Winterbottom, J., Tschofenig, H., and M. Thomson, “Location URI Contexts in HTTP-Enabled Location Delivery (HELD),” October 2009.).

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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

3.  Capabilities Exchange Overview

Acquiring location measurements or information from a device is made difficult by the nature of the relationship between the LIS, or access network, and the device. The relationship between a LIS and the devices that it serves is often transient. A device is not necessarily a permanent part of an access network.

HELD (Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, “HTTP Enabled Location Delivery (HELD),” August 2009.) [I‑D.ietf‑geopriv‑http‑location‑delivery] provides a basis for the relationship between device and LIS. LIS Discovery [I‑D.ietf‑geopriv‑lis‑discovery] (Thomson, M. and J. Winterbottom, “Discovering the Local Location Information Server (LIS),” March 2010.) provides a means for the device to initiate the relationship. The relationship is extended to include stateful information at the LIS in the form of a context (Winterbottom, J., Tschofenig, H., and M. Thomson, “Location URI Contexts in HTTP-Enabled Location Delivery (HELD),” October 2009.) [I‑D.winterbottom‑geopriv‑held‑context]. This document relies on the concept of a HELD context and provides a means for the LIS to acquire information from the device.

This document describes how the context can be used as the basis for cooperative location determination. A device provides the LIS with a capabilities indication when it creates or updates its context data. The LIS responds with a reciprocal indication, that includes which of these capabilities it might use. Depending on the specific capabilities that were shared and thereby agreed upon, the LIS is able to retrieve location information or location measurements from the device.

Device capabilities include the ability to generate or acquire location information, or the ability to make observations about the mode of network attachment or environment. For instance, a device with Global Navigation Satellite System (GNSS) hardware can determine its own position by taking a set of measurements and performing a calculation, or it can provide the GNSS measurement data.

This document defines a set of capabilities that a device can use to indicate that it is able to provide location measurements. The form of location measurements is described in [I‑D.thomson‑geopriv‑held‑measurements] (Thomson, M. and J. Winterbottom, “Using Device-provided Location-Related Measurements in Location Configuration Protocols,” October 2009.). A device is able to use these capabilities to indicate to the LIS the types of measurements that it can observe and the means by which the LIS can acquire these measurements when needed. Figure 1 (Basic Operation) shows a simple scenario where the LIS uses a device-provided measurement to service a request to a location URI.

  +--------+              +-------+          +-----------+
  |        |              |       |          | Location  |
  | Device |              |  LIS  |          | Recipient |
  +--------+              +-------+          +-----------+
      |                       |                    |
      +-----createContext---->|                    |
      |     (capabilities)    |                    |
      |                       |                    |
      |<----contextResponse---+                    |
      |     (capabilities)    |                    |
      |                       |                    |
      | ~ ~ ~ ~ ~ ~ (convey location URI) ~ ~ ~ ~ >|
      |                       |                    |
      |                       |<--locationRequest--+
      |                       |                    |
      |<--measurementRequest--+                    |
      |                       |                    |
      +--measurementResponse->|                    |
      |                       |                    |
      |                       +--locationResponse->|
      |                       |                    |

This document also defines a location capability, which indicates that the device is able to determine its own location. Guidelines for the definition of other capabilities are also included.

3.1.  Capabilities Exchange

To indicate capabilities to a LIS, a device sends a set of capabilities, each identified by a URN, to the LIS inside a HELD createContext request. The LIS selects those capabilities that it is able to make use of and includes those in the contextResponse message.

  +--------+                +-------+
  | Device |                |  LIS  |
  +--------+                +-------+
      |                         |
      +------createContext----->|
      |   (capability A, B, C)  |
      |                         |
      |<-----contextResponse----+
      |     (capability A, C)   |
      |                         |

The set of capabilities that the LIS includes in the response are a subset of the capabilities advertised by the Device. This is used to indicate which of the capabilities the LIS also supports, and therefore, the set of capabilities that the LIS might use.

Capabilities are related to a single context. The LIS MUST restrict its use of capabilities to requests relating to the context where the capabilities are provided by the Device. The LIS MUST remove any pre-existing capabilities from a context when it receives a capabilities indication. Therefore, a Device is able to remove specific capabilities from a context by providing a capabilities indication that omits that capability.

Once a common set of capabilities are agreed upon, the LIS is able to make use of these capabilities to generate location information. This might be an ability to generate geodetic location information at the device, or the device might be able provide the LIS with location measurements. The LIS invokes capabilities in response to a request for location information, which can be initiated by either the device, or a Location Recipient (LR).

  +--------+              +-------+          +-----------+
  |        |              |       |          | Location  |
  | Device |              |  LIS  |          | Recipient |
  +--------+              +-------+          +-----------+
      |                       |                    |
      |                       |<--locationRequest--+
      |                       |                    |
      |<--measurementRequest--+                    |
      |                       |                    |
      +--measurementResponse->|                    |
      |                       |                    |
      |                       +--locationResponse->|
      |                       |                    |

A capabilities exchange may contain additional information that is specific to the associated measurement acquisition method. This additional information allows the Device and LIS to provide more information about capabilities. Agreed capabilities and associated parameters can be stored in the context created for the device at the LIS for later use.

4.  The Capability Indication

A capabilities element is added to the create context or update context HELD requests. The device initiates the exchange, including the capabilities element in the request message. The response from the LIS includes a similar element that indicates which of these capabilities might be used.

A capabilities element contains a set of capability indications. A single capability is represented by a capind element. Each capind element has a mandatory uri attribute that contains a URI that uniquely identifies the type of capability. A id attribute identifies the individual capability; the value used by the LIS matches the corresponding indication by the Device.

The capind element may also contain arbitrary content, which means that the element is able to carry supplementary information that is specific to the capability. This supplementary information could include addressing information, protocol selection, authentication details, or any data necessary for the successful retrieval of information. Different supplementary information is provided by the Device and LIS.

The capind element has an additional optional parameter that indicates the expected time that exercising that particular capability takes. This information assists the LIS in a decision on whether or not to use this particular capability to serve a request for location information. Note that the Device is only able to quantify the time for its own involvement in the process; additional delays from network transmission and LIS processing need to be included in any decision to exercise a device capability. The responseTime attribute is specified as a time in milliseconds. The responseTime attribute SHOULD NOT be specified in a response from a LIS.

The following figure shows a capabilities indication that might be made by a device with GNSS capabilities. This uses the location capability defined in Section 5 (The Location Capability), as well as a second capability that includes additional parameters.

  <capabilities xmlns="urn:ietf:params:xml:ns:geopriv:held:cap">
    <capind uri="urn:ietf:params:xml:ns:geopriv:held:cap:location"
            id="cap-loc1" responseTime="45000">
      <url>https://192.0.2.55:46743/location/</url>
    </capind>
    <capind uri="urn:ietf:params:xml:ns:geopriv:held:cap:lm"
            id="cap-gnss1" responseTime="30000">
      <url>https://192.0.2.55:46743/gnss/</url>
      <lm xmlns:gnss="urn:ietf:params:xml:ns:geopriv:lm:gnss">
        gnss:gnss
      </lm>
    </capind>
  </capabilities>

4.1.  Retrieving Data from the Device

[[Author's Note: Alternatives to this approach are still being sought. A few unpromising options have been considered and rejected, so the issue remains open. This section states the current lowest common denominator option: namely failure to address the problem.]]

The capabilities described in this document both rely on the Device providing a URL. The LIS is able to dereference this URL in order to retrieve information from the device. The url element is included by the Device to indicate where (and how) the information is retrieved.

Although HELD can theoretically be bound to session protocols other than HTTP, in effect, HELD capabilities use the questionable practice of HTTP callbacks. For this particular application the drawbacks (primarily the fact that it doesn't work very reliably, aside from the general disdain it attracts) are considered acceptable for the following reasons:

• The LIS is expected to exist in close proximity to the device in the network, thereby reducing the probability that an intermediate node exists that could block the callback.
• The LIS is expected to hold a privileged position in the access network and may be able to resolve some of the shortcomings of this method.
• The benefit gained by acquiring measurements might be considered worthwhile despite a low probability of success.

4.2.  Capability Definitions

Capabilities can be defined for access network or location measurement technologies as required. No special registration is required to define a capability; each capability is identified by a namespace URI. A capability definition includes the following information:

URI:

A capability is identified by a URI, which need only be unique and persistent. Common practice is to use an http: URI for a domain that is under the author's control. An IETF document MUST use a URN (Moats, R., “URN Syntax,” May 1997.) [RFC2141] that is registered with the IANA.

Capability Parameters:

Each capability may require additional information to be passed between LIS and device in order for it to be exercised. This information must be described and defined as XML elements for inclusion in the capind element. Separate descriptions and definitions SHOULD be provided for the Device to LIS indications and LIS to Device responses.

Procedures for Exercising Capabilities:

Each capability MUST also include a description of how it can be exercised. This includes the protocol that is used for any network exchanges, the impact of each parameter.

Security and Privacy Implications:

A discussion of the security and the privacy implications associated with using the capability MUST be included with each definition.

Author Contact:

Details on how to contact the individual or organization responsible for the capability definition.

5.  The Location Capability

The ability to locate itself is a trait that is applicable to devices in a range of networks. This includes automated location determination, like Global Navigation Satellite Systems (GNSS), user input, an alternative location service, or a range of location techniques. Because the device produces complete location information, there is no need for technology- or network-specific features in messages. Therefore, this section describes how a device may advertise its capability to source its own location.

This section defines a location capability, identified by the URN urn:ietf:params:xml:ns:geopriv:held:cap:location. This capability indicates that the device is able to provide location information to the LIS.

The location capability includes a URI parameter that is passed in the request from Device to LIS. This URI is, in effect, a location URI that indicates where the LIS can retrieve location information. Any URI scheme that can be trivially resolved may be used when expressing this capability. It is RECOMMENDED that this be an https: or held: URI [[Author's Note: the held: URI is only tentatively included here, pending outcome of discussions on that (contentious) point]].

The URI provided by the Device should resolve to a PIDF-LO document (Peterson, J., “A Presence-based GEOPRIV Location Object Format,” December 2005.) [RFC4119] containing the location of the Device. The PIDF-LO MUST be current at the time that is requested. Only the location-info element of the PIDF-LO is used by the LIS; other PIDF-LO fields SHOULD be minimally populated.

If the provided URI is an http: URL, a GET request MUST yield a PIDF-LO in the response. If the URI is a held: URI, the LIS MUST follow the rules in [I‑D.winterbottom‑geopriv‑deref‑protocol] (Winterbottom, J., Tschofenig, H., Schulzrinne, H., Thomson, M., and M. Dawson, “A Location Dereferencing Protocol Using HELD,” January 2010.) when requesting information. The Device includes the PIDF-LO in a location response message.

In providing location information in this manner, the Device implicitly grants the LIS the ability to redistribute location information under the same conditions that apply to the HELD context.

5.1.  Location Capability Summary

The following summarizes the location capability following the outline from Section 4.2 (Capability Definitions):

URI:

urn:ietf:params:xml:ns:geopriv:held:cap:location

Capability Parameters:

This capability has a single parameter, a URL that is included in a url element. The url element is only used in the Device to LIS capabilities indication.

Procedures for Exercising Capabilities:

This capability is exercised by resolving and dereferencing a URL.

Security and Privacy Implications:

See Section 8 (Security Considerations) of this document.

Author Contact:

The authors of this document.

6.  Location Measurement Capability

Measurement data from the Device can be invaluable in improving the quality of location information. Measurement information from a device can improve the accuracy of location estimates or enable positioning methods that would not otherwise be available. See [I‑D.thomson‑geopriv‑held‑measurements] (Thomson, M. and J. Winterbottom, “Using Device-provided Location-Related Measurements in Location Configuration Protocols,” October 2009.) for more information on location measurements. Providing access to measurement data by using the capability exchange makes these advantages available when a location recipient uses a location URI to retrieve location information.

The measurement capability is identified by the URN urn:ietf:params:xml:ns:geopriv:held:cap:lm. In addition to this URN, the Device also needs to indicate which measurements it can provide in the capability indication. This is done by identifying the location measurement element.

The lm element includes a qualified element name (using the namespace context of the enclosing document). This name identifies a measurement element, as defined by the guidelines in [I‑D.thomson‑geopriv‑held‑measurements] (Thomson, M. and J. Winterbottom, “Using Device-provided Location-Related Measurements in Location Configuration Protocols,” October 2009.).

When the LIS dereferences the provided URL, the Device acquires location measurements and provides these in response. If an HTTP URI is provided, the response is an appplication/xml document containing a measurements element. If a HELD URI is used, the HELD measurement request and measurement response are used, as defined in Section 6.1 (HELD Measurement Request).

6.1.  HELD Measurement Request

A HELD measurement request is defined by a measurementRequest element. A HELD measurement request includes a qualified name of a measurement element in a lm element, which follows the same format as the same element in the capability indication. A responseTime attributes, which has the same semantics as the response time parameter on a location request (see [I‑D.ietf‑geopriv‑http‑location‑delivery] (Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, “HTTP Enabled Location Delivery (HELD),” August 2009.)), is also permitted. Figure 4 (Example Measurement Request) contains an example measurement request message.

  <measurementRequest xmlns="urn:ietf:params:xml:ns:geopriv:held:mr"
                      responseTime="3000">
    <lm xmlns="urn:ietf:params:xml:ns:geopriv:held:cap"
        xmlns:cell="urn:ietf:params:xml:ns:geopriv:lm:cell">
      cell:cellular
    </lm>
  </measurementRequest>

The measurement response contains a measurements element (see [I‑D.thomson‑geopriv‑held‑measurements] (Thomson, M. and J. Winterbottom, “Using Device-provided Location-Related Measurements in Location Configuration Protocols,” October 2009.)). Figure 5 (Example Measurement Response) contains an example measurement response message.

  <measurementResponse
      xmlns="urn:ietf:params:xml:ns:geopriv:held:mr">
     <measurements xmlns="urn:ietf:params:xml:ns:geopriv:lm"
                   time="2008-04-29T14:33:58">
       <cellular xmlns="urn:ietf:params:xml:ns:geopriv:lm:cell">
         <servingCell>
           <mcc>465</mcc><mnc>20</mnc>
           <csg>1234</csg><lcid>65000</lcid>
         </servingCell>
       </cellular>
     </measurements>
  </measurementResponse>

The HELD measurement request and response are defined in the urn:ietf:params:xml:ns:geopriv:held:mr namespace and use the application/held+xml MIME type.

For privacy purposes, the Device implicitly grants the LIS the ability to redistribute location information derived from the location measurements it provides under the same conditions that apply to the HELD context.

6.2.  Location Measurement Capability Summary

The following summarizes the location measurement capability following the outline from Section 4.2 (Capability Definitions):

URI:

urn:ietf:params:xml:ns:geopriv:held:cap:lm

Capability Parameters:

This capability has two parameters: a URL that is included in a url element; and a qualified element name that is included in the lm element. These parameters are only used in the Device to LIS capabilities indication.

Procedures for Exercising Capabilities:

This capability is exercised by resolving and dereferencing a URL. If the URL is a held: URL, a HELD measurement request (see Section 6.1 (HELD Measurement Request)) is used.

Security and Privacy Implications:

See Section 8 (Security Considerations) of this document.

Author Contact:

The authors of this document.

7.  XML Schema

This section includes a definition for the capabilities exchange element (Section 7.1 (Capabilities Schema)) and a definition of HELD measurement request and response messages (Section 7.2 (HELD Measurement Request Schema)).

7.1.  Capabilities Schema

<?xml version="1.0"?>
<xs:schema
     xmlns:cap="urn:ietf:params:xml:ns:geopriv:held:cap"
     xmlns:xs="http://www.w3.org/2001/XMLSchema"
     targetNamespace="urn:ietf:params:xml:ns:geopriv:held:cap"
     elementFormDefault="qualified"
     attributeFormDefault="unqualified">

  <xs:annotation>
    <xs:appinfo
        source="urn:ietf:params:xml:schema:geopriv:held:cap">
      HELD Capabilities
    </xs:appinfo>
    <xs:documentation source="http://www.ietf.org/rfc/rfcXXXX.txt">
<!-- [[NOTE TO RFC-EDITOR: Please replace above URL with URL of
                       published RFC and remove this note.]] -->
      This schema defines a framework for capabilities negotiation
      in HELD.
    </xs:documentation>
  </xs:annotation>

  <xs:element name="capabilities">
    <xs:complexType>
      <xs:complexContent>
        <xs:restriction base="xs:anyType">
          <xs:sequence>
            <xs:element ref="cap:capind"
                        minOccurs="0" maxOccurs="unbounded"/>
            <xs:any namespace="##other" processContents="lax"
                    minOccurs="0" maxOccurs="unbounded"/>
          </xs:sequence>
          <xs:anyAttribute namespace="##any" processContents="lax"/>
        </xs:restriction>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>

  <xs:element name="capind">
    <xs:complexType>
      <xs:complexContent>
        <xs:restriction base="xs:anyType">
          <xs:sequence>
            <xs:any namespace="##any" processContents="lax"
                    minOccurs="0" maxOccurs="unbounded"/>
          </xs:sequence>
          <xs:attribute name="id" type="xs:ID" use="required"/>
          <xs:attribute name="uri" type="xs:anyURI" use="required"/>
          <xs:attribute name="responseTime" type="xs:nonNegativeInteger"
                        use="optional"/>
          <xs:anyAttribute namespace="##any" processContents="lax"/>
        </xs:restriction>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>

  <!-- Location measurement element -->
  <xs:element name="lm" type="cap:lmType"/>
  <xs:complexType name="lmType">
    <xs:simpleContent>
      <xs:extension base="xs:Name">
        <xs:anyAttribute namespace="##any" processContents="lax"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>

  <!-- Callback URI element -->
  <xs:element name="url" type="xs:anyURI"/>

</xs:schema>

7.2.  HELD Measurement Request Schema

<?xml version="1.0"?>
<xs:schema
    xmlns:mr="urn:ietf:params:xml:ns:geopriv:held:mr"
    xmlns:held="urn:ietf:params:xml:ns:geopriv:held"
    xmlns:heldcap="urn:ietf:params:xml:ns:geopriv:held:cap"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="urn:ietf:params:xml:ns:geopriv:held:mr"
    elementFormDefault="qualified"
    attributeFormDefault="unqualified">

  <xs:annotation>
    <xs:appinfo
        source="urn:ietf:params:xml:schema:geopriv:held:mr">
      HELD Measurement Request and Response
    </xs:appinfo>
    <xs:documentation source="http://www.ietf.org/rfc/rfcXXXX.txt">
      <!-- [[NOTE TO RFC-EDITOR: Please replace above URL with URL of
           published RFC and remove this note.]] -->
      This schema defines the HELD measurement request and response.
    </xs:documentation>
  </xs:annotation>

  <xs:import namespace="urn:ietf:params:xml:ns:geopriv:held"/>
  <xs:import namespace="urn:ietf:params:xml:ns:geopriv:held:cap"/>

  <xs:element name="measurementRequest"
              type="mr:measurementRequestType"/>
  <xs:complexType name="measurementRequestType">
    <xs:complexContent>
      <xs:extension base="held:baseRequestType">
        <xs:sequence>
          <xs:element ref="heldcap:lm"/>
          <xs:any namespace="##any" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="measurementResponse" type="xs:anyType"/>

</xs:schema>

8.  Security Considerations

Giving the LIS additional information about the location of a Device might consititute a compromise of privacy. The LIS is able to resolve the location of the Device with greater accuracy than would be otherwise possible without this assistance. Information about the capabilities of a Device could also be considered sensitive. A Device SHOULD offer a user the option to suppress the capability exchange and all associated functions.

Capabilities MUST only be exchanged with the LIS in the scope of a context. This precaution provides the Device with a means to void access to these capabilities at any time. This can be done by deleting the context, or by indicating an empty set of capabilities to the LIS.

Any information that is provided to the LIS by the Device increases the impact of LIS impersonation. Measures that mitigate the possibility of impersonation, as outlined in [I‑D.ietf‑geopriv‑lis‑discovery] (Thomson, M. and J. Winterbottom, “Discovering the Local Location Information Server (LIS),” March 2010.), are more important for a Device that provides capability information to a LIS. Protocols used for the exchange of location information or location measurements should also provide protection from eavesdropping.

When the LIS contacts the Device, the Device SHOULD authenticate the LIS using the same credentials provided by the LIS after discovery (see [I‑D.ietf‑geopriv‑lis‑discovery] (Thomson, M. and J. Winterbottom, “Discovering the Local Location Information Server (LIS),” March 2010.)). This ensures that other entities are not able to retrieve location information or measurements from the Device. Requiring client authentication on a TLS connection and then matching this authentication to the server authentication provided by the LIS can achieve this.

The LIS is responsible for the veracity of location information it provides, even when it relies on information that comes from the Device. However, the LIS is not necessarily able to establish grounds for trust in this information. A Device could provide erroneous measurements in an attempt to make the LIS provide incorrect or fraudulent location information. The LIS should take measures to verify the information that is provided to it before acting on those data. The LIS can use information from the network, or other trusted sources, to check that information provided by the Device is valid.

9.  IANA Considerations

This section registers URNs for XML namespaces of capabilities (Section 9.1 (URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap)) and the HELD measurement request and response (Section 9.5 (URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:mr)). Corresponding schemas are also registered (Section 9.4 (XML Schema Registration for HELD Capabilities), Section 9.6 (XML Schema Registration for HELD Measurement Request and Response)). URNs are registered for the location (Section 9.2 (URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:location)) and location measurement (Section 9.3 (URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:lm)) capability URIs.

9.1.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap

This section registers a new XML namespace, urn:ietf:params:xml:ns:held:cap, as per the guidelines in [RFC3688] (Mealling, M., “The IETF XML Registry,” January 2004.).

URI: urn:ietf:params:xml:ns:held:cap

Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.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>HELD Capabilities Indication</title>
          </head>
          <body>
            <h1>Namespace for HELD Capabilities Indication</h1>
            <h2>urn:ietf:params:xml:ns:held:cap</h2>
[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
    with the RFC number for this specification.]]
            <p>See <a href="[[RFC URL]]">RFCXXXX</a>.</p>
          </body>
        </html>
      END

9.2.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:location

This section registers a new XML namespace, urn:ietf:params:xml:ns:held:cap:location, as per the guidelines in [RFC3688] (Mealling, M., “The IETF XML Registry,” January 2004.).

URI: urn:ietf:params:xml:ns:held:cap:location

Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.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>HELD Capabilities - Location Capability</title>
          </head>
          <body>
            <h1>Namespace for HELD Capabilities
                - Location Capability</h1>
            <h2>urn:ietf:params:xml:ns:held:cap:location</h2>
[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
    with the RFC number for this specification.]]
            <p>See <a href="[[RFC URL]]">RFCXXXX</a>.</p>
          </body>
        </html>
      END

9.3.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:lm

This section registers a new XML namespace, urn:ietf:params:xml:ns:held:cap:lm, as per the guidelines in [RFC3688] (Mealling, M., “The IETF XML Registry,” January 2004.).

URI: urn:ietf:params:xml:ns:held:cap:lm

Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.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>HELD Capabilities
                   - Location Measurement Capability</title>
          </head>
          <body>
            <h1>Namespace for HELD Capabilities
                - Location Measurement Capability</h1>
            <h2>urn:ietf:params:xml:ns:held:cap:lm</h2>
[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
    with the RFC number for this specification.]]
            <p>See <a href="[[RFC URL]]">RFCXXXX</a>.</p>
          </body>
        </html>
      END

9.4.  XML Schema Registration for HELD Capabilities

This section registers an XML schema as per the guidelines in [RFC3688] (Mealling, M., “The IETF XML Registry,” January 2004.).

URI:

urn:ietf:params:xml:schema:held:cap

Registrant Contact:

IETF, GEOPRIV working group, (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.com).

Schema:

The XML for this schema can be found as the entirety of Section 7.1 (Capabilities Schema) of this document.

9.5.  URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:mr

This section registers a new XML namespace, urn:ietf:params:xml:ns:held:mr, as per the guidelines in [RFC3688] (Mealling, M., “The IETF XML Registry,” January 2004.).

URI: urn:ietf:params:xml:ns:held:mr

Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.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>HELD Measurement Request/Response</title>
          </head>
          <body>
            <h1>Namespace for HELD Request/Response</h1>
            <h2>urn:ietf:params:xml:ns:held:mr</h2>
[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
    with the RFC number for this specification.]]
            <p>See <a href="[[RFC URL]]">RFCXXXX</a>.</p>
          </body>
        </html>
      END

9.6.  XML Schema Registration for HELD Measurement Request and Response

This section registers an XML schema as per the guidelines in [RFC3688] (Mealling, M., “The IETF XML Registry,” January 2004.).

URI:

urn:ietf:params:xml:schema:held:mr

Registrant Contact:

IETF, GEOPRIV working group, (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.com).

Schema:

The XML for this schema can be found as the entirety of Section 7.2 (HELD Measurement Request Schema) of this document.

10.  References

10.1. Normative References

10.2. Informative References

Authors' Addresses