Internet DRAFT - draft-fossati-core-geo-link-format-attribute

draft-fossati-core-geo-link-format-attribute







Internet Engineering Task Force                               T. Fossati
Internet-Draft                                            Alcatel-Lucent
Intended status: Standards Track                       February 12, 2014
Expires: August 16, 2014


              A Link-Format Attribute for Locating Things
            draft-fossati-core-geo-link-format-attribute-03

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 defined to allow
   the discovery of resources based on their geo location.

Status of This Memo

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   This Internet-Draft will expire on August 16, 2014.

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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 . . . . . . . . . . . . . . . . . . .   4
   6.  Extended Geo Queries  . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.2.  Filtering Rules . . . . . . . . . . . . . . . . . . . . .   5
     6.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

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 (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









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   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.

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 sensor exposing an explicit location resource:

     REQ: GET /.well-known/core?geo=*

     RES: 2.05 Content
     </loc>;geo="52.2047, 0.1368"


   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?geo=*

     RES: 2.05 Content
     </fire>;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?geo=*

     RES: 2.05 Content
     </water>;ct=0;if="sensor";geo="38.2953,20.6426,-20;u=10"






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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 "extended" geo query (xgeo) format allows a client application to
   select a capture area, and let endpoints advertise their presence --
   by replying to the link-format query -- if they are located within
   the specified area.

6.1.  Syntax

   The syntax for describing the query capture area is based on the "WGS
   84 bounding box" defined in section 10.2.2 of [OGC-WSC].

   The WGS 84 bounding box is a specialisation of the more general
   bounding box concept for use with the WGS 84 geodetic datum, with
   latitude and longitude expressed as decimal degrees.

   A bounding box is a rectangular area identified by its lower and
   upper corners, i.e. the points within the bounding box at which the
   value of each coordinate is the algebraic minimum and maximum,
   respectively.

   For consistency with the geo URI definition, the latitude and
   longitude attributes of the upper and lower corners have been
   swapped, while the optional 'crs' and 'dimensions' parameters are not
   used (their default values are implicitly assumed), which leads to
   the following ABNF:

        ext-geo-query = "?xgeo=" bounding-box
        bounding-box  = lower-corner "-" upper-corner
        lower-corner  = latitude "," longitude
        upper-corner  = latitude "," longitude


   For simplicity, xgeo allows a single bounding box per link-format
   query.  Therefore, when a search is logically made of multiple boxes
   (e.g. at a discontinuity point, or for more complex tessellations),
   the querying client shall split it into the appropriate number of
   xgeo queries and send them out individually.





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6.2.  Filtering Rules

   An endpoint which understands xgeo MUST respond to the query if and
   only if its latitude and longitude values fall within the bounding
   box specified in the query string.

   When running the match algorithm, the queried endpoint MUST take into
   consideration any accuracy/uncertainty associated with its current
   position.  Any uncertainty information MUST be returned in a response
   if it has been used to compute a positive answer to the corresponding
   xgeo query.

6.3.  Examples

   o  An example capture area that would match (among the other) the "/
      water" resource in Section 4:

     REQ: GET /.well-known/core?xgeo=38.2900,20.6400-38.3000,20.6500

     RES[0]: 2.05 Content
     </water>;geo="38.2953,20.6426,-20;u=10"

     RES[1]: 2.05 Content
     </pos>;geo="38.2908,20.6451"

     RES[2]: [...]



7.  Acknowledgements

   Thanks to Keith Drage and Carl Reed 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].






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   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.

10.  Normative References

   [OGC-WSC]  Whiteside, A. and J. Greenwood, "OGC Web Service Common
              Implementation Specification (Version 2.0.0)", April 2010,
              <http://http://www.opengeospatial.org/standards/common>.

   [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











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