GEOPRIV M. Thomson
Internet-Draft J. Winterbottom
Intended status: Standards Track Andrew
Expires: January 4, 2009 July 3, 2008
Device Capability Negotiation for Device-Based Location Determination
and Location Measurements in HELD
draft-thomson-geopriv-held-capabilities-04
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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 described.
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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 . . . . . . . . . . . . . . . . . . 6
4.1. Retrieving Data from the Device . . . . . . . . . . . . . 8
4.2. Capability Definitions . . . . . . . . . . . . . . . . . . 8
5. The Location Capability . . . . . . . . . . . . . . . . . . . 9
5.1. Location Capability Summary . . . . . . . . . . . . . . . 10
6. Location Measurement Capability . . . . . . . . . . . . . . . 10
6.1. HELD Measurement Request . . . . . . . . . . . . . . . . . 11
6.2. Location Measurement Capability Summary . . . . . . . . . 11
7. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Capabilities Schema . . . . . . . . . . . . . . . . . . . 12
7.2. HELD Measurement Request Schema . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:held:cap . . . . . . . . . . . . . 15
9.2. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:held:cap:location . . . . . . . . . 16
9.3. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:held:cap:lm . . . . . . . . . . . . 17
9.4. XML Schema Registration for HELD Capabilities . . . . . . 18
9.5. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:held:mr . . . . . . . . . . . . . . 18
9.6. XML Schema Registration for HELD Measurement Request
and Response . . . . . . . . . . . . . . . . . . . . . . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . . 20
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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
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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 GNSS-capable hardware can
determine its own position by taking a set of measurements and
performing a calculation, or it can provide the raw 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.
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+--------+ +-------+ +-----------+
| | | | | 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
At its core, the capabilities exchange is simple. The 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
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The set of capabilities that the LIS includes in the response are a
subset of the capabilities advertised by the Device.
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 and
pre-existing capabilities from a context when it receives a
capabilities indication. Therefore, a Device is able to remove
capabilities from a context by providing an empty capabilities set.
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.
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
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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 identifies the capability.
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, as well as a second capability that
includes additional parameters.
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 January 4, 2009 [Page 16] Internet-Draft HELD Capabilities July 2008 BEGINSee 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 January 4, 2009 [Page 17] Internet-Draft HELD Capabilities July 2008 BEGINSee 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 January 4, 2009 [Page 18] Internet-Draft HELD Capabilities July 2008 BEGINSee 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-07 (work in progress), April 2008. Thomson & Winterbottom Expires January 4, 2009 [Page 19] Internet-Draft HELD Capabilities July 2008 [I-D.ietf-geopriv-lis-discovery] Thomson, M. and J. Winterbottom, "Discovering the Local Location Information Server (LIS)", draft-ietf-geopriv-lis- discovery-01 (work in progress), June 2008. [I-D.winterbottom-geopriv-held-context] Winterbottom, J., Tschofenig, H., and M. Thomson, "HELD Protocol Context Management Extensions", draft- winterbottom-geopriv-held- context-02 (work in progress), February 2008. [I-D.thomson-geopriv-held-measurements] Thomson, M. and J. Winterbottom, "Using Device-provided Location- Related Measurements in HELD", draft-thomson- geopriv-held-measurements- 02 (work in progress), May 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-00 (work in progress), November 2007. 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. [RFC4119] Peterson, J., "A Presence- based GEOPRIV Location Thomson & Winterbottom Expires January 4, 2009 [Page 20] Internet-Draft HELD Capabilities July 2008 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-01 (work in progress), June 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 January 4, 2009 [Page 21] Internet-Draft HELD Capabilities July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Thomson & Winterbottom Expires January 4, 2009 [Page 22]