GEOPRIV M. Thomson Internet-Draft J. Winterbottom Intended status: Standards Track Andrew Expires: July 19, 2009 January 15, 2009 Device Capability Negotiation for Device-Based Location Determination and Location Measurements in HELD draft-thomson-geopriv-held-capabilities-05 Status of This Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on July 19, 2009. Copyright Notice Copyright (c) 2009 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. Abstract A framework for the exchange of capabilities in HELD is described. Thomson & Winterbottom Expires July 19, 2009 [Page 1] Internet-Draft HELD Capabilities January 2009 Capabilities for enabling device-based measurements and device-based location generation are defined based on this framework. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 3 3. Capabilities Exchange Overview . . . . . . . . . . . . . . . . 3 3.1. Capabilities Exchange . . . . . . . . . . . . . . . . . . 5 4. The Capability Indication . . . . . . . . . . . . . . . . . . 7 4.1. Retrieving Data from the Device . . . . . . . . . . . . . 8 4.2. Capability Definitions . . . . . . . . . . . . . . . . . . 9 5. The Location Capability . . . . . . . . . . . . . . . . . . . 9 5.1. Location Capability Summary . . . . . . . . . . . . . . . 10 6. Location Measurement Capability . . . . . . . . . . . . . . . 11 6.1. HELD Measurement Request . . . . . . . . . . . . . . . . . 11 6.2. Location Measurement Capability Summary . . . . . . . . . 12 7. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1. Capabilities Schema . . . . . . . . . . . . . . . . . . . 13 7.2. HELD Measurement Request Schema . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 9.1. URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap . . . . . . . . . . . . . 17 9.2. URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:location . . . . . . . . . 17 9.3. URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:cap:lm . . . . . . . . . . . . 18 9.4. XML Schema Registration for HELD Capabilities . . . . . . 19 9.5. URN Sub-Namespace Registration for urn:ietf:params:xml:ns:held:mr . . . . . . . . . . . . . . 19 9.6. XML Schema Registration for HELD Measurement Request and Response . . . . . . . . . . . . . . . . . . . . . . . 20 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 10.1. Normative References . . . . . . . . . . . . . . . . . . . 20 10.2. Informative References . . . . . . . . . . . . . . . . . . 21 Thomson & Winterbottom Expires July 19, 2009 [Page 2] Internet-Draft HELD Capabilities January 2009 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]. 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]). 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]. Location measurement is defined in [I-D.thomson-geopriv-held-measurements] and location estimate is defined in [I-D.thomson-geopriv-uncertainty]. The term context is used as defined in [I-D.winterbottom-geopriv-held-context]. 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]. 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 [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] provides a means for the device to Thomson & Winterbottom Expires July 19, 2009 [Page 3] Internet-Draft HELD Capabilities January 2009 initiate the relationship. The relationship is extended to include stateful information at the LIS in the form of a context [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]. 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 shows a simple scenario where the LIS uses a device-provided measurement to service a request to a location URI. Thomson & Winterbottom Expires July 19, 2009 [Page 4] Internet-Draft HELD Capabilities January 2009 +--------+ +-------+ +-----------+ | | | | | Location | | Device | | LIS | | Recipient | +--------+ +-------+ +-----------+ | | | +-----createContext---->| | | (capabilities) | | | | | |<----contextResponse---+ | | (capabilities) | | | | | | ~ ~ ~ ~ ~ ~ (convey location URI) ~ ~ ~ ~ >| | | | | |<--locationRequest--+ | | | |<--measurementRequest--+ | | | | +--measurementResponse->| | | | | | +--locationResponse->| | | | Figure 1: Basic Operation 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) | | | Figure 2: Capabilities Exchange Thomson & Winterbottom Expires July 19, 2009 [Page 5] Internet-Draft HELD Capabilities January 2009 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->| | | | Figure 3: Exercising Capabilities 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. Thomson & Winterbottom Expires July 19, 2009 [Page 6] Internet-Draft HELD Capabilities January 2009 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. Thomson & Winterbottom Expires July 19, 2009 [Page 7] Internet-Draft HELD Capabilities January 2009 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, as well as a second capability that includes additional parameters. https://192.0.2.55:46743/location/ https://192.0.2.55:46743/gnss/ gnss:gnss 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: o 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. o 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. Thomson & Winterbottom Expires July 19, 2009 [Page 8] Internet-Draft HELD Capabilities January 2009 o 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 [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 Thomson & Winterbottom Expires July 19, 2009 [Page 9] Internet-Draft HELD Capabilities January 2009 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 [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] 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: 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 of this document. Author Contact: The authors of this document. Thomson & Winterbottom Expires July 19, 2009 [Page 10] Internet-Draft HELD Capabilities January 2009 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] 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]. 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. 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]), is also permitted. Figure 4 contains an example measurement request message. Thomson & Winterbottom Expires July 19, 2009 [Page 11] Internet-Draft HELD Capabilities January 2009 cell:cellular Figure 4: Example Measurement Request The measurement response contains a "measurements" element (see [I-D.thomson-geopriv-held-measurements]). Figure 5 contains an example measurement response message. 46520 123465000 Figure 5: Example Measurement Response 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: URI: urn:ietf:params:xml:ns:geopriv:held:cap:lm Thomson & Winterbottom Expires July 19, 2009 [Page 12] Internet-Draft HELD Capabilities January 2009 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) is used. Security and Privacy Implications: See Section 8 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) and a definition of HELD measurement request and response messages (Section 7.2). 7.1. Capabilities Schema HELD Capabilities This schema defines a framework for capabilities negotiation in HELD. Thomson & Winterbottom Expires July 19, 2009 [Page 14] Internet-Draft HELD Capabilities January 2009 7.2. HELD Measurement Request Schema HELD Measurement Request and Response This schema defines the HELD measurement request and response. Thomson & Winterbottom Expires July 19, 2009 [Page 15] Internet-Draft HELD Capabilities January 2009 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], 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]). 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) and the HELD measurement request and response (Section 9.5). Corresponding schemas are also registered Thomson & Winterbottom Expires July 19, 2009 [Page 16] Internet-Draft HELD Capabilities January 2009 (Section 9.4, Section 9.6). URNs are registered for the location (Section 9.2) and location measurement (Section 9.3) 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]. 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 HELD Capabilities Indication

Namespace for HELD Capabilities Indication

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

[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX with the RFC number for this specification.]]

See RFCXXXX.

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]. 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: Thomson & Winterbottom Expires July 19, 2009 [Page 17] Internet-Draft HELD Capabilities January 2009 BEGIN HELD Capabilities - Location Capability

Namespace for HELD Capabilities - Location Capability

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

[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX with the RFC number for this specification.]]

See RFCXXXX.

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]. 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: Thomson & Winterbottom Expires July 19, 2009 [Page 18] Internet-Draft HELD Capabilities January 2009 BEGIN HELD Capabilities - Location Measurement Capability

Namespace for HELD Capabilities - Location Measurement Capability

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

[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX with the RFC number for this specification.]]

See RFCXXXX.

END 9.4. XML Schema Registration for HELD Capabilities This section registers an XML schema as per the guidelines in [RFC3688]. 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 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]. URI: urn:ietf:params:xml:ns:held:mr Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.com). XML: Thomson & Winterbottom Expires July 19, 2009 [Page 19] Internet-Draft HELD Capabilities January 2009 BEGIN HELD Measurement Request/Response

Namespace for HELD Request/Response

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

[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX with the RFC number for this specification.]]

See RFCXXXX.

END 9.6. XML Schema Registration for HELD Measurement Request and Response This section registers an XML schema as per the guidelines in [RFC3688]. 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 of this document. 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. [I-D.ietf-geopriv-http-location-delivery] Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, "HTTP Enabled Location Delivery (HELD)", draft-ietf-geopriv-http- location-delivery-11 (work in progress), Thomson & Winterbottom Expires July 19, 2009 [Page 20] Internet-Draft HELD Capabilities January 2009 December 2008. [I-D.ietf-geopriv-lis-discovery] Thomson, M. and J. Winterbottom, "Discovering the Local Location Information Server (LIS)", draft-ietf-geopriv-lis- discovery-05 (work in progress), December 2008. [I-D.winterbottom-geopriv-held-context] Winterbottom, J., Tschofenig, H., and M. Thomson, "HELD Protocol Context Management Extensions", draft- winterbottom-geopriv-held- context-03 (work in progress), September 2008. [I-D.thomson-geopriv-held-measurements] Thomson, M. and J. Winterbottom, "Using Device-provided Location- Related Measurements in Location Configuration Protocols", draft-thomson- geopriv-held-measurements- 03 (work in progress), October 2008. [I-D.winterbottom-geopriv-deref-protocol] Winterbottom, J., Tschofenig, H., Schulzrinne, H., Thomson, M., and M. Dawson, "An HTTPS Location Dereferencing Protocol Using HELD", draft- winterbottom-geopriv- deref-protocol-02 (work in progress), July 2008. 10.2. Informative References [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. Thomson & Winterbottom Expires July 19, 2009 [Page 21] Internet-Draft HELD Capabilities January 2009 [RFC4119] Peterson, J., "A Presence- based GEOPRIV Location Object Format", RFC 4119, December 2005. [I-D.thomson-geopriv-uncertainty] Thomson, M. and J. Winterbottom, "Representation of Uncertainty and Confidence in PIDF-LO", draft- thomson-geopriv- uncertainty-02 (work in progress), November 2008. Authors' Addresses Martin Thomson Andrew PO Box U40 Wollongong University Campus, NSW 2500 AU Phone: +61 2 4221 2915 EMail: martin.thomson@andrew.com URI: http://www.andrew.com/ James Winterbottom Andrew PO Box U40 Wollongong University Campus, NSW 2500 AU Phone: +61 2 4221 2938 EMail: james.winterbottom@andrew.com URI: http://www.andrew.com/ Thomson & Winterbottom Expires July 19, 2009 [Page 22]