A Link-Format Attribute for Locating Things

Abstract

This memo proposes a new CoAP link format attribute, "geo", that can be used to associate positioning metadata to a CoAP resource.¶

1. Introduction

This memo proposes a new CoAP link-format attribute, "geo", that can be used to associate positioning metadata to a CoAP resource, and make this information available to other endpoints that, directly or indirectly, participate in to CoAP link-format discovery [RFC6690].¶

The ability for a consuming application to access positioning information about a sensing resource is crucial in a number of use cases, especially those in which one or more sensor networks provide input to an emergency handling service (e.g. fire, flood, etc.).¶

This spec reuses the geo URI syntax [RFC5870], which is capable to describe physical locations in two or three dimensions (also supporting underground and underwater localisation using negative numbers) in a compact, simple and human readable way.¶

2. Motivation and Use Cases

Location-aware applications and location-based services like seismic networks, gas pipeline monitoring deployments, fire or flood detection systems, etc., need to precisely locate the source of sensed stimulus in order to react in a sensible way.¶

{TODO collect other use cases}¶

3. The geo Link Format Attribute

This section defines a new Web Linking [RFC5988] link-param, "geo", to be used within the [RFC6690] framework, having the following syntax:¶

  link-extension  = "geo" "=" geo-path
  geo-path          ; defined in Section 3.3. of RFC 5870

The geo attribute MUST NOT appear more than once in a link.¶

(NOTE about Link-Format queries: non exact matches cannot be easily/effectively queried.)¶

4. Examples

• A fire detector somewhere in the Pollino National Park (approx. 10cm accuracy, enough to distinguish trees from each other):¶

  REQ: GET /.well-known/core

  RES: 2.05 Content
  </fire>;ct=0;if="sensor;geo="40.00201,16.34007"

• An underwater current sampler in the sea between Ithaki and Kefallonia (approx. 10m accuracy):¶

  REQ: GET /.well-known/core

  RES: 2.05 Content
  </water>;ct=0;if="sensor;geo="38.2953,20.6426,-20"

5. Encoding Considerations

See Section 3.5. of [RFC5870].¶

6. IANA Considerations

TODO¶

7. Security Considerations

The "geo" link-format attributes share the same security issues as any other attribute involved in the discovery process described in [RFC6690].¶

Further to that, the privacy considerations regarding distribution, protection, usage, retention, and storage of the location information of the target resource found in [RFC6280] fully apply.¶

8. Normative References

[RFC2119]

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.

[RFC3694]

Danley, M., Mulligan, D., Morris, J., and J. Peterson, "Threat Analysis of the Geopriv Protocol", RFC 3694, DOI 10.17487/RFC3694, February 2004, <https://www.rfc-editor.org/info/rfc3694>.

[RFC5870]

Mayrhofer, A. and C. Spanring, "A Uniform Resource Identifier for Geographic Locations ('geo' URI)", RFC 5870, DOI 10.17487/RFC5870, June 2010, <https://www.rfc-editor.org/info/rfc5870>.

[RFC5988]

Nottingham, M., "Web Linking", RFC 5988, DOI 10.17487/RFC5988, October 2010, <https://www.rfc-editor.org/info/rfc5988>.

[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, DOI 10.17487/RFC6280, July 2011, <https://www.rfc-editor.org/info/rfc6280>.

[RFC6690]

Shelby, Z., "Constrained RESTful Environments (CoRE) Link Format", RFC 6690, DOI 10.17487/RFC6690, August 2012, <https://www.rfc-editor.org/info/rfc6690>.