Internet Engineering Task Force T. Fossati Internet-Draft Alcatel-Lucent Intended status: Standards Track January 05, 2014 Expires: July 09, 2014 A Link-Format Attribute for Locating Things draft-fossati-core-geo-link-format-attribute-02 Abstract This memo proposes a new CoAP link format attribute, "geo", that can be used to associate positioning metadata to a CoAP resource. An extension to the link format query syntax is also suggested to allow the discovery of resources based on their geo location. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Fossati Expires July 09, 2014 [Page 1] Internet-Draft The geo Link-Format Attribute January 2014 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. The geo Link Format Attribute . . . . . . . . . . . . . . . . 3 4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5. Encoding Considerations . . . . . . . . . . . . . . . . . . . 3 6. Extended Geo Queries . . . . . . . . . . . . . . . . . . . . 3 6.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.2. Filtering Rules . . . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 9. Security Considerations . . . . . . . . . . . . . . . . . . . 4 10. Normative References . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction The ability for a client application to access positioning information about a sensing resource is crucial in a number of use cases, e.g. those in which one or more sensor networks provide input to an emergency handling service (e.g. fire, flood, etc.). 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 to CoAP link-format discovery [RFC6690]. This spec reuses the geo URI syntax [RFC5870], which is capable of describing physical locations in two or three dimensions (also supporting underground and underwater localisation using negative numbers) in a simple, reasonably compact, and human readable way. 1.1. Requirements Language 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]. 2. Use Cases Location-aware applications and location-based services like rescue systems in devastated areas, 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 suitable way. Smart city scenarios, e.g. street lights control, emergency services, often have similar needs. Fossati Expires July 09, 2014 [Page 2] Internet-Draft The geo Link-Format Attribute January 2014 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. 4. Examples o 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 ;ct=0;if="sensor";geo="40.00201,16.34007" o An underwater current sampler in the sea between Ithaki and Kefallonia bearing explicit accuracy information (10m): REQ: GET /.well-known/core RES: 2.05 Content ;ct=0;if="sensor";geo="38.2953,20.6426,-20;u=10" 5. Encoding Considerations This specification allows only one CRS, which is WGS-84. There is no need to set an explicit crslabel when encoding a geo link-format attribute, since the default value wgs84 applies anyway. For further encoding consideration, see Section 3.5. of [RFC5870]. 6. Extended Geo Queries The query filtering rules defined in Section 4.1. of [RFC6690] are not particularly well suited for querying resources based on geo parameters. Therefore, this memo specifies an extended set of query formatting and filtering rules specific for the geo attribute. Fossati Expires July 09, 2014 [Page 3] Internet-Draft The geo Link-Format Attribute January 2014 By means of the "extended" geo query format, a client application can make resources pop up in link-format responses based on their location. 6.1. Syntax The query parameters are the top left and the bottom right corners of a rectangular sector representing the query "capture" area. The two points (top left, bottom right respectively) are expressed as comma- delimited latitude/longitude pairs, separated by a dash "-": "?geo=" latitude "," longitude "-" latitude "," longitude latitude ; defined in Section 3.3. of RFC 5870 longitude ; defined in Section 3.3. of RFC 5870 6.2. Filtering Rules An endpoint which understands the extended geo query format MUST respond to the query if and only if its latitude and longitude values fall in the latitude and longitude range defined by the query string. Any accuracy/uncertainty MUST be taken into consideration by the queried endpoint when running the match algorithm. For example, the "/water" resource in Section 4 would match the query "?geo=38.3000,20.6400-38.2900,20.6500" 7. Acknowledgements Thanks to Keith Drage for comments and discussions that have helped shaping this document. 8. IANA Considerations No formal request at present. However, there is a plan to add a registry for the namespace of link parameters as part of [RFC5988] update. 9. Security Considerations The "geo" link-format attribute shares 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. Fossati Expires July 09, 2014 [Page 4] Internet-Draft The geo Link-Format Attribute January 2014 10. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3694] Danley, M., Mulligan, D., Morris, J., and J. Peterson, "Threat Analysis of the Geopriv Protocol", RFC 3694, February 2004. [RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource Identifier for Geographic Locations ('geo' URI)", RFC 5870, June 2010. [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. [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. [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link Format", RFC 6690, August 2012. Author's Address Thomas Fossati Alcatel-Lucent 3 Ely Road Milton, Cambridge CB24 6DD UK Email: thomas.fossati@alcatel-lucent.com Fossati Expires July 09, 2014 [Page 5]