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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force T. Fossati 3 Internet-Draft Alcatel-Lucent 4 Intended status: Standards Track February 12, 2014 5 Expires: August 16, 2014 7 A Link-Format Attribute for Locating Things 8 draft-fossati-core-geo-link-format-attribute-03 10 Abstract 12 This memo proposes a new CoAP link format attribute, "geo", that can 13 be used to associate positioning metadata to a CoAP resource. An 14 extension to the link format query syntax is also defined to allow 15 the discovery of resources based on their geo location. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on August 16, 2014. 34 Copyright Notice 36 Copyright (c) 2014 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 53 2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 2 54 3. The geo Link Format Attribute . . . . . . . . . . . . . . . . 3 55 4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 5. Encoding Considerations . . . . . . . . . . . . . . . . . . . 4 57 6. Extended Geo Queries . . . . . . . . . . . . . . . . . . . . 4 58 6.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 6.2. Filtering Rules . . . . . . . . . . . . . . . . . . . . . 5 60 6.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 5 61 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 62 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 63 9. Security Considerations . . . . . . . . . . . . . . . . . . . 5 64 10. Normative References . . . . . . . . . . . . . . . . . . . . 6 65 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 67 1. Introduction 69 The ability for a client application to access positioning 70 information about a sensing resource is crucial in a number of use 71 cases, e.g. those in which one or more sensor networks provide input 72 to an emergency handling service (fire, flood, etc.). 74 This memo proposes a new CoAP link-format attribute, "geo", that can 75 be used to associate positioning metadata to a CoAP resource, and 76 make this information available to other endpoints that, directly or 77 indirectly, participate to CoAP link-format discovery [RFC6690]. 79 This spec reuses the geo URI syntax [RFC5870], which is capable of 80 describing physical locations in two or three dimensions (also 81 supporting underground and underwater localisation using negative 82 numbers) in a simple, reasonably compact, and human readable way. 84 1.1. Requirements Language 86 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 87 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 88 document are to be interpreted as described in [RFC2119]. 90 2. Use Cases 91 Location-aware applications and location-based services like rescue 92 systems in devastated areas, seismic networks, gas pipeline 93 monitoring deployments, fire or flood detection systems, etc., need 94 to precisely locate the source of sensed stimulus in order to react 95 in a suitable way. Smart city scenarios, e.g. street lights control, 96 emergency services, often have similar needs. 98 3. The geo Link Format Attribute 100 This section defines a new Web Linking [RFC5988] link-param, "geo", 101 to be used within the [RFC6690] framework, having the following 102 syntax: 104 link-extension = "geo" "=" geo-path 105 geo-path ; defined in Section 3.3. of RFC 5870 107 The geo attribute MUST NOT appear more than once in a link. 109 4. Examples 111 o A sensor exposing an explicit location resource: 113 REQ: GET /.well-known/core?geo=* 115 RES: 2.05 Content 116 ;geo="52.2047, 0.1368" 118 o A fire detector somewhere in the Pollino National Park (approx. 119 10cm accuracy, enough to distinguish trees from each other): 121 REQ: GET /.well-known/core?geo=* 123 RES: 2.05 Content 124 ;ct=0;if="sensor";geo="40.00201,16.34007" 126 o An underwater current sampler in the sea between Ithaki and 127 Kefallonia bearing explicit accuracy information (10m): 129 REQ: GET /.well-known/core?geo=* 131 RES: 2.05 Content 132 ;ct=0;if="sensor";geo="38.2953,20.6426,-20;u=10" 134 5. Encoding Considerations 136 This specification allows only one CRS, which is WGS-84. There is no 137 need to set an explicit crslabel when encoding a geo link-format 138 attribute, since the default value wgs84 applies anyway. 140 For further encoding consideration, see Section 3.5. of [RFC5870]. 142 6. Extended Geo Queries 144 The "extended" geo query (xgeo) format allows a client application to 145 select a capture area, and let endpoints advertise their presence -- 146 by replying to the link-format query -- if they are located within 147 the specified area. 149 6.1. Syntax 151 The syntax for describing the query capture area is based on the "WGS 152 84 bounding box" defined in section 10.2.2 of [OGC-WSC]. 154 The WGS 84 bounding box is a specialisation of the more general 155 bounding box concept for use with the WGS 84 geodetic datum, with 156 latitude and longitude expressed as decimal degrees. 158 A bounding box is a rectangular area identified by its lower and 159 upper corners, i.e. the points within the bounding box at which the 160 value of each coordinate is the algebraic minimum and maximum, 161 respectively. 163 For consistency with the geo URI definition, the latitude and 164 longitude attributes of the upper and lower corners have been 165 swapped, while the optional 'crs' and 'dimensions' parameters are not 166 used (their default values are implicitly assumed), which leads to 167 the following ABNF: 169 ext-geo-query = "?xgeo=" bounding-box 170 bounding-box = lower-corner "-" upper-corner 171 lower-corner = latitude "," longitude 172 upper-corner = latitude "," longitude 174 For simplicity, xgeo allows a single bounding box per link-format 175 query. Therefore, when a search is logically made of multiple boxes 176 (e.g. at a discontinuity point, or for more complex tessellations), 177 the querying client shall split it into the appropriate number of 178 xgeo queries and send them out individually. 180 6.2. Filtering Rules 182 An endpoint which understands xgeo MUST respond to the query if and 183 only if its latitude and longitude values fall within the bounding 184 box specified in the query string. 186 When running the match algorithm, the queried endpoint MUST take into 187 consideration any accuracy/uncertainty associated with its current 188 position. Any uncertainty information MUST be returned in a response 189 if it has been used to compute a positive answer to the corresponding 190 xgeo query. 192 6.3. Examples 194 o An example capture area that would match (among the other) the "/ 195 water" resource in Section 4: 197 REQ: GET /.well-known/core?xgeo=38.2900,20.6400-38.3000,20.6500 199 RES[0]: 2.05 Content 200 ;geo="38.2953,20.6426,-20;u=10" 202 RES[1]: 2.05 Content 203 ;geo="38.2908,20.6451" 205 RES[2]: [...] 207 7. Acknowledgements 209 Thanks to Keith Drage and Carl Reed for comments and discussions that 210 have helped shaping this document. 212 8. IANA Considerations 214 No formal request at present. However, there is a plan to add a 215 registry for the namespace of link parameters as part of [RFC5988] 216 update. 218 9. Security Considerations 220 The "geo" link-format attribute shares the same security issues as 221 any other attribute involved in the discovery process described in 222 [RFC6690]. 224 Further to that, the privacy considerations regarding distribution, 225 protection, usage, retention, and storage of the location information 226 of the target resource found in [RFC6280] fully apply. 228 10. Normative References 230 [OGC-WSC] Whiteside, A. and J. Greenwood, "OGC Web Service Common 231 Implementation Specification (Version 2.0.0)", April 2010, 232 . 234 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 235 Requirement Levels", BCP 14, RFC 2119, March 1997. 237 [RFC3694] Danley, M., Mulligan, D., Morris, J., and J. Peterson, 238 "Threat Analysis of the Geopriv Protocol", RFC 3694, 239 February 2004. 241 [RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource 242 Identifier for Geographic Locations ('geo' URI)", RFC 243 5870, June 2010. 245 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. 247 [RFC6280] Barnes, R., Lepinski, M., Cooper, A., Morris, J., 248 Tschofenig, H., and H. Schulzrinne, "An Architecture for 249 Location and Location Privacy in Internet Applications", 250 BCP 160, RFC 6280, July 2011. 252 [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link 253 Format", RFC 6690, August 2012. 255 Author's Address 257 Thomas Fossati 258 Alcatel-Lucent 259 3 Ely Road 260 Milton, Cambridge CB24 6DD 261 UK 263 Email: thomas.fossati@alcatel-lucent.com