Network Working Group                                           C. Hopps
Internet-Draft                                   LabN Consulting, L.L.C.
Intended status: Standards Track                        November 4, 2019                        13 February 2020
Expires: May 7, 16 August 2020

                           YANG Geo Location
                   draft-ietf-netmod-geo-location-02
                   draft-ietf-netmod-geo-location-03

Abstract

   This document defines a generic geographical location object YANG
   grouping.  The geographical location grouping is intended to be used
   in YANG models for specifying a location on or in reference to the
   Earth or any other astronomical object.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on May 7, 16 August 2020.

Copyright Notice

   Copyright (c) 2019 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  The Geo Location Object . . . . . . . . . . . . . . . . . . .   3
     2.1.  Frame of Reference  . . . . . . . . . . . . . . . . . . .   3
     2.2.  Location  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Motion  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.4.  Nested Locations  . . . . . . . . . . . . . . . . . . . .   5
     2.5.  Non-location Attributes . . . . . . . . . . . . . . . . .   5
     2.6.  Tree  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  ISO 6709:2008 Conformance . . . . . . . . . . . . . . . . . .  11
   5.  Usability . . . . . . . . . . . . . . . . . . . . . . . . . .  12
     5.1.  Portability . . . . . . . . . . . . . . . . . . . . . . .  13
       5.1.1.  IETF URI Value  . . . . . . . . . . . . . . . . . . .  13
       5.1.2.  W3C . . . . . . . . . . . . . . . . . . . . . . . . .  13
       5.1.3.  Geography Markup Language (GML) . . . . . . . . . . .  15
       5.1.4.  KML . . . . . . . . . . . . . . . . . . . . . . . . .  15  16
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     6.1.  Geodetic System Value Registry  . . . . . . . . . . . . .  16
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   8.  Normative References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Normative
   9.  Informative References  . . . . . . . . . . . . . . . . . .  18
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  19
   Appendix B.  Acknowledgements . . . . . . . . . . . . . . . . . .  22
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  23  22

1.  Introduction

   In many applications we would like to specify the location of
   something geographically.  Some examples of locations in networking
   might be the location of data center, a rack in an internet exchange
   point, a router, a firewall, a port on some device, or it could be
   the endpoints of a fiber, or perhaps the failure point along a fiber.

   Additionally, while this location is typically relative to The Earth,
   it does not need to be.  Indeed it is easy to imagine a network or
   device located on The Moon, on Mars, on Enceladus (the moon of
   Saturn) or even a comet (e.g., 67p/churyumov-gerasimenko).

   Finally, one can imagine defining locations using different frames of
   reference or even alternate systems (e.g., simulations or virtual
   realities).

   This document defines a "geo-location" YANG grouping that allows for
   all of the above data to be captured.

   This specification conforms to [ISO.6709.2008].

   The YANG data model described in this document conforms to the
   Network Management Datastore Architecture defined in [RFC8342].

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119] [RFC8174] when, and only when, they appear in all capitals,
   as shown here.

2.  The Geo Location Object

2.1.  Frame of Reference

   The frame of reference ("reference-frame") defines what the location
   values refer to and their meaning.  The referred to object can be any
   astronomical body.  It could be a planet such as The Earth or Mars, a
   moon such as Enceladus, an asteroid such as Ceres, or even a comet
   such as 1P/Halley.  This value is specified in "astronomical-body"
   and is defined by the International Astronomical Union
   (<http://www.iau.org>),
   (http://www.iau.org), The default "astronomical-body" value is
   "earth".

   In addition to identifying the astronomical body we also need to
   define the meaning of the coordinates (e.g., latitude and longitude)
   and the definition of 0-height.  This is done with a "geodetic-datum"
   value.  The default value for "geodetic-datum" is "wgs-84" (i.e., the
   World Geodetic System, [WGS84]), which is used by the Global
   Positioning System (GPS) among many others.  We define an IANA
   registry for specifying standard values for the "geodetic-datum".

   In addition to the "geodetic-datum" value we allow refining the
   coordinate and height accuracy using "coord-accuracy" and "height-
   accuracy" respectively.  When specified these values override the
   defaults implied by the "geodetic-datum" value.

   Finally, we define an optional feature which allows for changing the
   system for which the above values are defined.  This optional feature
   adds an "alternate-system" value to the reference frame.  This value
   is normally not present which implies the natural universe is the
   system.  The use of this value is intended to allow for creating
   virtual realities or perhaps alternate coordinate systems.  The
   definition of alternate systems is outside the scope of this
   document.

2.2.  Location

   This is the location on or relative to the astronomical object.  It
   is specified using 2 or 3 coordinates values.  These values are given
   either as "latitude", "longitude", and an optional "height", or as
   Cartesian coordinates of "x", "y" and an optional "z".  For the standard location
   choice "latitude" and "longitude" are specified as fractions of
   decimal degrees, and the "height" value is in fractions of meters.
   For the Cartesian choice "x", "y" and "z" are in fractions of meters.
   In both choices the exact meanings of all of the values are defined
   by the "geodetic-datum" value in the Section 2.1.

2.3.  Motion

   Support is added for objects in relatively stable motion.  For
   objects in relatively stable motion the grouping provides a
   3-dimensional vector value.  The components of the vector are
   "v-north", "v-east" and "v-up" which are all given in fractional
   meters per second.  The values "v-north" and "v-east" are relative to
   true-north as defined by the reference frame for the astronomical
   body, "v-up" is perpendicular to the plane defined by "v-north" and
   "v-east", and is pointed away from the center of mass.

   To derive the 2-dimensional heading and speed one would use the
   following formulas:

                 ,------------------------------
       speed =  V  v_{north}^{2} + v_{east}^{2}

       heading = arctan(v_{east} / v_{north})

   For some applications that demand high accuracy, and where the data
   is infrequently updated this velocity vector can track very slow
   movement such as continental drift.

   Tracking more complex forms of motion is outside the scope of this
   work.  The intent of the grouping being defined here is to identify
   where something is located, and generally this is expected to be
   somewhere on or relative to the Earth (or another astronomical body).
   At least two options are available to YANG models that wish to use
   this grouping with objects that are changing location frequently in
   non-simple ways, they can add additional motion data to their model
   directly, or if the application allows it can require more frequent
   queries to keep the location data current.

2.4.  Nested Locations

   When locations are nested (e.g., a building may have a location which
   houses routers that also have locations) the module using this
   grouping is free to indicate in its definition that the "reference-
   frame" is inherited from the containing object so that the
   "reference-frame" need not be repeated in every instance of location
   data.

2.5.  Non-location Attributes

   During the development of this module, the question of whether it
   would support data such as orientation arose.  These types of
   attributes are outside the scope of this grouping because they do not
   deal with a location but rather describe something more about the
   object that is at the location.  Module authors are free to add these
   non-location attributes along with their use of this location
   grouping.

2.6.  Tree

   The following is the YANG tree diagram [RFC8340] for the geo-location
   grouping.

     module: ietf-geo-location
       grouping geo-location
         +-- geo-location
            +-- reference-frame
            |  +-- alternate-system?    string {alternate-systems}?
            |  +-- astronomical-body?   string
            |  +-- geodetic-system
            |     +-- geodetic-datum?    string
            |     +-- coord-accuracy?    decimal64
            |     +-- height-accuracy?   decimal64
            +-- (location)?
            |  +--:(ellipsoid)
            |  |  +-- latitude?    degrees    decimal64
            |  |  +-- longitude?   degrees   decimal64
            |  |  +-- height?      decimal64
            |  +--:(cartesian)
            |     +-- x?           decimal64
            |     +-- y?           decimal64
            |     +-- z?           decimal64
            +-- velocity
            |  +-- v-north?   decimal64
            |  +-- v-east?    decimal64
            |  +-- v-up?      decimal64
            +-- timestamp?         types:date-and-time

                 Figure 1: Geo Location YANG tree diagram.
            +-- valid-until?       types:date-and-time

3.  YANG Module

   <CODE BEGINS> file "ietf-geo-location@2019-02-17.yang"
   module ietf-geo-location {
     namespace "urn:ietf:params:xml:ns:yang:ietf-geo-location";
     prefix geo;
     import ietf-yang-types { prefix types; }

     organization
       "IETF NETMOD Working Group (NETMOD)";
     contact
       "Christian Hopps <chopps@chopps.org>";

     // RFC Ed.: replace XXXX with actual RFC number and
     // remove this note.

     description
       "This module defines a grouping of a container object for
        specifying a location on or around an astronomical object (e.g.,
        The Earth).

        Copyright (c) 2019 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.

        // RFC Ed.: replace XXXX with actual RFC number and
        // remove this note.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
        'MAY', and 'OPTIONAL' in this document are to be interpreted as
        described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.";

     revision 2019-02-17 {
       description "Initial Revision";
       reference "RFC XXXX: YANG Geo Location";
     }

     typedef degrees {
       type decimal64 {
         fraction-digits 16;
       }
       units "decimal degrees";
       description "Coordinate value.";
     }

     feature alternate-systems {
       description
         "This feature means the device supports specifying locations
          using alternate systems for reference frames.";
     }

     grouping geo-location {
      description
         "Grouping to identify a location on an astronomical object.";

       container geo-location {
         description
           "A location on an astronomical body (e.g., The Earth)
            somewhere in a universe.";

         container reference-frame {
           description
             "The Frame of Reference for the location values.";

           leaf alternate-system {
             if-feature alternate-systems;
             type string;
             description
               "The system in which the astronomical body and
                geodetic-datum is defined. Normally, this value is not
                present and the system is the natural universe; however,
                when present this value allows for specifying alternate
                systems (e.g., virtual realities). An alternate-system
                modifies the definition (but not the type) of the other
                values in the reference frame.";
           }
           leaf astronomical-body {
             type string {
               pattern '[ -@\[-\^_-~]*';
             }
             default "earth";
             description
               "An astronomical body as named by the International
                Astronomical Union (IAU) or according to the alternate
                system if specified. Examples include 'sun' (our star),
                'earth' (our planet), 'moon' (our moon), 'enceladus' (a
                moon of Saturn), 'ceres' (an asteroid),
                '67p/churyumov-gerasimenko (a comet). The value should
                be comprised of all lower case ASCII characters not
                including control characters (i.e., values 32..64, and
                91..126). Any preceding 'the' in the name should not be
                included.";
           }
           container geodetic-system {
             description
               "The geodetic system of the location data.";
             leaf geodetic-datum {
               type string {
                 pattern '[ -@\[-\^_-~]*';
               }
               default "wgs-84";
               description
                 "A geodetic-datum defining the meaning of latitude,
                  longitude and height. The default is 'wgs-84' which is
                  used by the Global Positioning System (GPS). The value
                  SHOULD be comprised of all lower case ASCII characters
                  not including control characters (i.e., values 32..64,
                  and 91..126). The IANA registry further restricts the
                  value by converting all spaces (' ') to dashes ('-')";
             }
             leaf coord-accuracy {
               type decimal64 {
                 fraction-digits 6;
               }
               description
                 "The accuracy of the latitude longitude pair. pair for
                  ellipsoidal coordinates, or the X, Y and Z components
                  for Cartesian coordinates. When coord-accuracy is
                  specified it overrides the geodetic-datum implied accuracy. If Cartesian
                  coordinates are in use this accuracy corresponds to
                  the X and Y components";
                  accuracy.";
             }
             leaf height-accuracy {
               type decimal64 {
                 fraction-digits 6;
               }
               units "meters";
               description
                 "The accuracy of height value. value for ellipsoidal
                  coordinates, this value is not used with Cartesian
                  coordinates. When specified it overrides the
                  geodetic-datum implied default. If
                  Cartesian coordinates ar in use this accuracy
                  corresponds to the Z component.";
             }
             // May wish to allow for height to be relative.
             // If so need to decide if we have a boolean (to ground)
             // or an enumeration (e.g., local ground, sea-floor,
             // ground floor, containing object, ...) or even allow
             // for a string for most generic but least portable
             // comparable
             // leaf height-relative {
             // default.";
             }
           }
         }
         choice location {
           description
             "The location data either in lat/long or Cartesian values";
           case ellipsoid {
             leaf latitude {
               type degrees; decimal64 {
                 fraction-digits 16;
               }
               units "decimal degrees";
               description
                 "The latitude value on the astronomical body. The
                  definition and precision of this measurement is
                  indicated by the reference-frame value.";
             }
             leaf longitude {
               type degrees; decimal64 {
                 fraction-digits 16;
               }
               units "decimal degrees";
               description
                 "The longitude value on the astronomical body. The
                  definition and precision of this measurement is
                  indicated by the reference-frame.";
             }
             leaf height {
               type decimal64 {
                 fraction-digits 6;
               }
               units "meters";
               description
                 "Height from a reference 0 value. The precision and '0'
                  value is defined by the reference-frame.";
             }
           }
           case cartesian {
             leaf x {
               type decimal64 {
                 fraction-digits 6;
               }
               units "meters";
               description
                 "The X value as defined by the reference-frame.";
             }
             leaf y {
               type decimal64 {
                 fraction-digits 6;
               }
               units "meters";
               description
                 "The Y value as defined by the reference-frame.";
             }
             leaf z {
               type decimal64 {
                 fraction-digits 6;
               }
               units "meters";
               description
                 "The Z value as defined by the reference-frame.";
             }
           }
         }
         container velocity {
           description
             "If the object is in motion the velocity vector describes
              this motion at the the time given by the timestamp."; timestamp";

           leaf v-north {
             type decimal64 {
               fraction-digits 12;
             }
             units "meters per second";
             description
               "v-north is the rate of change (i.e., speed) towards
                truth north as defined by the ~geodetic-system~.";
           }
           leaf v-east {
             type decimal64 {
               fraction-digits 12;
             }
             units "meters per second";
             description
               "v-east is the rate of change (i.e., speed) perpendicular
                to truth-north as defined by the ~geodetic-system~.";
           }

           leaf v-up {
             type decimal64 {
               fraction-digits 12;
             }
             units "meters per second";
             description
               "v-up is the rate of change (i.e., speed) away from the
                center of mass.";
           }
         }
         leaf timestamp {
           type types:date-and-time;
           description "Reference time when location was recorded.";
         }
         leaf valid-until {
           type types:date-and-time;
           description
             "The timestamp for which this geo-location is valid until.
              If unspecified the geo-location has no specific expiration
              time.";
         }
       }
     }
   }
   <CODE ENDS>

4.  ISO 6709:2008 Conformance

   [ISO.6709.2008] provides an appendix with a set of tests for
   conformance to the standard.  The tests and results are given in the
   following table along with an explanation of non-applicable tests.

   +---------+-----------------------------------+---------------------+

           +---------+----------------------+------------------+
           | Test    | Description          | Pass Explanation |
   +---------+-----------------------------------+---------------------+
           +=========+======================+==================+
           | A.1.2.1 | elements reqd. for a geo. point | CRS is always    |
           |         | geo. point location  | indicated        |
   |         |                                   |                     |
           +---------+----------------------+------------------+
           | A.1.2.2 | Description of a CRS from a | CRS register is  |
           |         | from a register      | defined          |
   |         |                                   |                     |
           +---------+----------------------+------------------+
           | A.1.2.3 | definition of CRS    | N/A - Don't define      |
           |         |                      | define CRS       |
   |         |                                   |                     |
           +---------+----------------------+------------------+
           | A.1.2.4 | representation of horizontal    | lat/long values  |
           |         | horizontal position  | conform          |
   |         |                                   |                     |
           +---------+----------------------+------------------+
           | A.1.2.5 | representation of vertical    | height value     |
           |         | vertical position    | conforms         |
   |         |                                   |                     |
           +---------+----------------------+------------------+
           | A.1.2.6 | text string representation          | N/A - No string  |
           |         | representation       | format           |
   +---------+-----------------------------------+---------------------+
           +---------+----------------------+------------------+

                     Table 1: Conformance Test Results

   For test "A.1.2.1" the YANG geo location object either includes a CRS
   ("reference-frame") or has a default defined ([WGS84]).

   For "A.1.2.3" we do not define our own CRS, and doing so is not
   required for conformance.

   For "A.1.2.6" we do not define a text string representation, which is
   also not required for conformance.

5.  Usability

   The geo-location object defined in this document and YANG module have
   been designed to be usable in a very broad set of applications.  This
   includes the ability to locate things on astronomical bodies other
   than The Earth, and to utilize entirely different coordinate systems
   and realities.

   Many systems make use of geo-location data, and so it's important to
   be able describe this data using this geo-location object defined in
   this document.

5.1.  Portability

   In order to verify portability while developing this module the
   following standards and standard APIs and were considered.

5.1.1.  IETF URI Value

   [RFC5870] defines a standard URI value for geographic location data.
   It includes the ability to specify the "geodetic-value" (it calls
   this "crs") with the default being "wgs-84" [WGS84].  For the
   location data it allows 2 to 3 coordinates defined by the "crs"
   value.  For accuracy it has a single "u" parameter for specifying
   uncertainty.  The "u" value is in fractions of meters and applies to
   all the location values.  As the URI is a string, all values are
   specifies as strings and so are capable of as much precision as
   required.

   URI values can be mapped to and from the YANG grouping, with the
   caveat that some loss of precision (in the extremes) may occur due to
   the YANG grouping using decimal64 values rather than strings.

5.1.2.  W3C

   See <https://w3c.github.io/geolocation-api/#dom-geolocationposition>. https://w3c.github.io/geolocation-api/#dom-geolocationposition.

   W3C Defines a geo-location API in [W3CGEO].  We show a snippet of
   code below which defines the geo-location data for this API.  This is
   used by many application (e.g., Google Maps API).

   interface GeolocationPosition {
     readonly attribute GeolocationCoordinates coords;
     readonly attribute DOMTimeStamp timestamp;
   };

   interface GeolocationCoordinates {
     readonly attribute double latitude;
     readonly attribute double longitude;
     readonly attribute double? altitude;
     readonly attribute double accuracy;
     readonly attribute double? altitudeAccuracy;

     readonly attribute double? speed;
   };

             Figure 2: 1: Snippet Showing Geo-Location Definition

5.1.2.1.  Compare with YANG Model

    +------------------+--------------+-----------------+-------------+
    | Field            | Type         | YANG            | Type        |
    +------------------+--------------+-----------------+-------------+
    +==================+==============+=================+=============+
    | accuracy         | double       | coord-accuracy  | dec64 fr 6  |
    |                  |              |                 |             |
    +------------------+--------------+-----------------+-------------+
    | altitude         | double       | height          | dec64 fr 6  |
    |                  |              |                 |             |
    +------------------+--------------+-----------------+-------------+
    | altitudeAccuracy | double       | height-accuracy | dec64 fr 6  |
    |                  |              |                 |             |
    +------------------+--------------+-----------------+-------------+
    | heading          | double       | heading v-north, v-east | dec64 fr 16 |
    |                  |              |                 | 12 |
    +------------------+--------------+-----------------+-------------+
    | latitude         | double       | latitude        | dec64 fr 16 |
    |                  |              |                 |             |
    +------------------+--------------+-----------------+-------------+
    | longitude        | double       | longitude       | dec64 fr 16 |
    |                  |              |                 |             |
    +------------------+--------------+-----------------+-------------+
    | speed            | double       | speed v-north, v-east | dec64 fr 12 |
    |                  |              |                 |             |
    +------------------+--------------+-----------------+-------------+
    | timestamp        | DOMTimeStamp | timestamp       | string      |
    +------------------+--------------+-----------------+-------------+

                                  Table 2

   accuracy (double): (double)  Accuracy of "latitude" and "longitude" values in
      meters.

   altitude (double): (double)  Optional height in meters above the [WGS84]
      ellipsoid.

   altitudeAccuracy (double): (double)  Optional accuracy of "altitude" value in
      meters.

   heading (double): (double)  Optional Direction in decimal deg from true north
      increasing clock-wise.

   latitude, longitude (double): (double)  Standard lat/long values in decimal
      degrees.

   speed (double): (double)  Speed along heading in meters per second.

   timestamp (DOMTimeStamp): (DOMTimeStamp)  Specifies milliseconds since the Unix EPOCH
      in 64 bit unsigned integer.  The YANG model defines the timestamp
      with arbitrarily large precision by using a string which
      encompasses all representable values of this timestamp value.

   W3C API values can be mapped to the YANG grouping, with the caveat
   that some loss of precision (in the extremes) may occur due to the
   YANG grouping using decimal64 values rather than doubles.

   Conversely, only YANG values for The Earth using the default "wgs-84"
   [WGS84] as the "geodetic-datum", can be directly mapped to the W3C
   values, as W3C does not provide the extra features necessary to map
   the broader set of values supported by the YANG grouping.

5.1.3.  Geography Markup Language (GML)

   ISO adopted the Geography Markup Language (GML) defined by OGC 07-036
   as [ISO.19136.2007].  GML defines, among many other things, a
   position type "gml:pos" which is a sequence of "double" values.  This
   sequence of values represent coordinates in a given CRS.  The CRS is
   either inherited from containing elements or directly specified as
   attributes "srsName" and optionally "srsDimension" on the "gml:pos".

   GML defines an Abstract CRS type which Concrete CRS types derive
   from.  This allows for many types of CRS definitions.  We are
   concerned with the Geodetic CRS type which can have either
   ellipsoidal or Cartesian coordinates.  We believe that other non-
   Earth based CRS as well as virtual CRS should also be representable
   by the GML CRS types as well.

   Thus GML "gml:pos" values can be mapped directly to the YANG
   grouping, with the caveat that some loss of precision (in the
   extremes) may occur due to the YANG grouping using decimal64 values
   rather than doubles.

   Conversely, YANG grouping values can be mapped to GML as directly as
   the GML CRS available definitions allow with a minimum of Earth-based
   geodetic systems fully supported.

   GML also defines an observation value in "gml:Observation" which
   includes a timestamp value "gml:validTime" in addition to other
   components such as "gml:using" "gml:target" and "gml:resultOf".  Only
   the timestamp is mappable to and from the YANG grouping.  Furthermore
   "gml:validTime" can either be an Instantaneous measure
   ("gml:TimeInstant") or a time period ("gml:TimePeriod").  Only the  The
   instantaneous "gml:TimeInstant" is mappable to and from the YANG
   grouping "timestamp" value, and values down to the resolution of
   seconds for "gml:TimePeriod" can be mapped using the using the
   "valid-for" node of the YANG grouping.

5.1.4.  KML

   KML 2.2 [KML22] (formerly Keyhole Markup Language) was submitted by
   Google to Open Geospatial Consortium (OGC)
   <https://www.opengeospatial.org/>
   https://www.opengeospatial.org/ and was adopted.  The latest version
   as of this writing is KML 2.3 [KML23].  This schema includes
   geographic location data in some of it's its objects (e.g., <kml:Point "kml:Point" or
   <kml:Camera>
   "kml:Camera" objects).  This data is provided in string format and
   corresponds to the [W3CGEO] values.  The timestamp value is also
   specified as a string as in our YANG grouping.

   KML has some special handling for the height value useful for
   visualization software, "kml:altitudeMode".  These values for
   "kml:altitudeMode" include indicating the height is ignored
   ("clampToGround"), in relation to the locations location's ground level
   ("relativeToGround"), or in relation to the geodetic datum
   ("absolute").  The YANG grouping can directly map the ignored and
   absolute cases, but not the relative to ground case.

   In addition to the "kml:altitudeMode" KML also defines two seafloor
   height values using "kml:seaFloorAltitudeMode".  One value is to
   ignore the height value ("clampToSeaFloor") and the other is relative
   ("relativeToSeaFloor").  As with the "kml:altitudeMode" value, the
   YANG grouping supports the ignore case but not the relative case.

   The KML location values use a geodetic datum defined in Annex A by
   the GML Coordinate Reference System (CRS) [ISO.19136.2007] with
   identifier "LonLat84_5773".  The altitude value for KML absolute
   height mode is measured from the vertical datum specified by [WGS84].

   Thus the YANG grouping and KML values can be directly mapped in both
   directions (when using a supported altitude mode) with the caveat
   that some loss of precision (in the extremes) may occur due to the
   YANG grouping using decimal64 values rather than strings.  For the
   relative height cases the application doing the transformation is
   expected to have the data available to transform the relative height
   into an absolute height which can then be expressed using the YANG
   grouping.

6.  IANA Considerations

6.1.  Geodetic System Value Registry

   This registry allocates names for standard geodetic systems.  Often
   these values are referred to using multiple names (e.g., full names
   or multiple acronyms values).  The intent of this registry is to
   provide a single standard value for any given geodetic system.

   The values SHOULD use an acronym when available, they MUST be
   converted to lower case, and spaces MUST be changed to dashes "-".

   Each entry should be sufficient to define the 3 coordinate values (2
   if height is not required).  So for example the "wgs-84" is defined
   as WGS-84 with the geoid updated by at least [EGM96] for height
   values.  Specific entries for [EGM96] and [EGM08] are present if a
   more precise definition of the data is required.

   It should be noted that [RFC5870] also creates a registry for
   Geodetic Systems (it calls CRS); however, this registry has a very
   strict modification policy.  The authors of [RFC5870] have the stated
   goal of making CRS registration hard to avoid proliferation of CRS
   values.  As our module defines alternate systems and has a broader
   (beyond earth) scope, the registry defined below is meant to be more
   easily modified.

   TODO: Open question, should we create a new registry here or attempt
   to modify the one created by [RFC5870].  It's worth noting that we
   include the ability to specify any geodetic system including ones
   designed for astronomical bodies other than the earth, as well as
   ones based on alternate systems.  These requirements may be too broad
   for adapting the existing [RFC5870] registry.

   TODO: Open question, is FCFS too easy, perhaps expert review would
   strike a good balance.  If expert review is acceptable, would it also
   be acceptable to update the policy on [RFC5870] and use it instead?

   The allocation policy for this registry is First Come First Served,
   [RFC8126] as the intent is simply to avoid duplicate values.

   The initial values for this registry are as follows.

   +------------+------------------------------------------------------+
   | Name       | Description                                          |
   +------------+------------------------------------------------------+
   +============+======================================================+
   | me         | Mean Earth/Polar Axis (Moon)                         |
   |            |                                                      |
   +------------+------------------------------------------------------+
   | mola-vik-1 | MOLA Height, IAU Viking-1 PM (Mars)                  |
   |            |                                                      |
   +------------+------------------------------------------------------+
   | wgs-84-96  | World Geodetic System 1984 [WGS84] w/ EGM96          |
   |            |                                                      |
   +------------+------------------------------------------------------+
   | wgs-84-08  | World Geodetic System 1984 [WGS84] w/ [EGM08]        |
   |            |                                                      |
   +------------+------------------------------------------------------+
   | wgs-84     | World Geodetic System 1984 [WGS84] (EGM96 or         |
   |            | better)                                              |
   +------------+------------------------------------------------------+

                                  Table 3

7.  Security Considerations

   This document defines a common geo location grouping using the YANG
   data modeling language.  The grouping itself has no security or
   privacy impact on the Internet, but the usage of the grouping in
   concrete YANG modules might have.  The security considerations
   spelled out in the YANG 1.1 specification [RFC7950] apply for this
   document as well.

8.  References

8.1.  Normative References

   [EGM08]    Pavlis, N., N.K., Holmes, S., S.A., Kenyon, S., S.C., and J. J.K. Factor,
              "An Earth Gravitational Model to Degree 2160: EGM08.",
              Presented at the 2008 General Assembly of the European
              Geosciences Union, Vienna, Arpil13-18, 2008, 2008,
              <http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/
              egm08_wgs84.html>.

   [EGM96]    Lemoine, F., F.G., Kenyon, S., S.C., Factor, J., J.K., Trimmer, R., R.G.,
              Pavlis,
              N., N.K., Chinn, D., D.S., Cox, C., C.M., Klosko, S., S.M.,
              Luthcke, S., S.B., Torrence,
              M., M.H., Wang, Y., Y.M., Williamson, R.,
              R.G., Pavlis, E., E.C., Rapp, R., R.H., and T. T.R. Olson, "The
              Development of the Joint NASA GSFC and the National
              Imagery and Mapping Agency (NIMA) Geopotential Model
              EGM96.", Technical Report NASA/TP-1998-206861, NASA,
              Greenbelt., 1998,
              <https://cddis.nasa.gov/926/egm96/egm96.html>.

   [ISO.6709.2008]
              International Organization for Standardization, "ISO
              6709:2008 Standard representation of geographic point
              location by coordinates.", 2008.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [WGS84]    National Imagery and Mapping Agency., "National Imagery
              and Mapping Agency Technical Report 8350.2, Third
              Edition.", 1 3 January 2000, <http://earth-
              info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf>.

8.2.

9.  Informative References

   [ISO.19136.2007]
              International Organization for Standardization, "ISO
              19136:2007 Geographic information -- Geography Markup
              Language (GML)".

   [KML22]    Wilson, T., Ed., "OGC KML (Version 2.2)", 4 14 April 2008,
              <http://portal.opengeospatial.org/
              files/?artifact_id=27810>.

   [KML23]    Burggraf, D., Ed., "OGC KML 2.3", 8 4 August 2015,
              <http://docs.opengeospatial.org/
              is/12-007r2/12-007r2.html>.

   [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>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [W3CGEO]   Popescu, A., "Geolocation API Specification", 11 8 November
              2016,
              <https://www.w3.org/TR/2016/
              REC-geolocation-API-20161108/>. <https://www.w3.org/TR/2016/REC-geolocation-API-
              20161108/>.

Appendix A.  Examples

   Below is a fictitious module that uses the geo-location grouping.

   module example-uses-geo-location {
     namespace
       "urn:example:example-uses-geo-location";
     prefix ugeo;
     import ietf-geo-location { prefix geo; }
     organization "Empty Org";
     contact "Example Author <eauthor@example.com>";
     description "Example use of geo-location";
     revision 2019-02-02 { reference "None"; }
     container locatable-items {
       description "container of locatable items";
       list locatable-item {
         key name;
         description "A of locatable item";
         leaf name {
           type string;
           description "name of locatable item";
         }
         uses geo:geo-location;
       }
     }
   }

             Figure 3: 2: Example YANG module using geo location.

   Below is a the YANG tree for the fictitious module that uses the geo-
   location grouping.

     module: example-uses-geo-location
       +--rw locatable-items
          +--rw locatable-item* [name]
             +--rw name            string
             +--rw geo-location
                +--rw reference-frame
                |  +--rw alternate-system?    string {alternate-systems}?
                |  +--rw astronomical-body?   string
                |  +--rw geodetic-system
                |     +--rw geodetic-datum?    string
                |     +--rw coord-accuracy?    decimal64
                |     +--rw height-accuracy?   decimal64
                +--rw (location)?
                |  +--:(ellipsoid)
                |  |  +--rw latitude?    degrees    decimal64
                |  |  +--rw longitude?   degrees   decimal64
                |  |  +--rw height?      decimal64
                |  +--:(cartesian)
                |     +--rw x?           decimal64
                |     +--rw y?           decimal64
                |     +--rw z?           decimal64
                +--rw velocity
                |  +--rw v-north?   decimal64
                |  +--rw v-east?    decimal64
                |  +--rw v-up?      decimal64
                +--rw timestamp?         types:date-and-time
                +--rw valid-until?       types:date-and-time

   Below is some example YANG XML data for the fictitious module that
   uses the geo-location grouping.

   <ns0:config xmlns:ns0="urn:ietf:params:xml:ns:netconf:base:1.0">

   <locatable-items xmlns="urn:example:example-uses-geo-location">
     <locatable-item>
       <name>Gaetana's</name>
       <geo-location>
         <latitude>40.73297</latitude>
         <longitude>-74.007696</longitude>
       </geo-location>
     </locatable-item>
     <locatable-item>
       <name>Pont des Arts</name>
       <geo-location>
         <timestamp>2012-03-31T16:00:00Z</timestamp>
         <latitude>48.8583424</latitude>
         <longitude>2.3375084</longitude>
         <height>35</height>
       </geo-location>
     </locatable-item>
     <locatable-item>
       <name>Saint Louis Cathedral</name>
       <geo-location>
         <timestamp>2013-10-12T15:00:00-06:00</timestamp>
         <latitude>29.9579735</latitude>
         <longitude>-90.0637281</longitude>
       </geo-location>
     </locatable-item>
     <locatable-item>
       <name>Apollo 11 Landing Site</name>
       <geo-location>
         <timestamp>1969-07-21T02:56:15Z</timestamp>
         <reference-frame>
           <astronomical-body>moon</astronomical-body>
           <geodetic-system>
             <geodetic-datum>me</geodetic-datum>
           </geodetic-system>
         </reference-frame>
         <latitude>0.67409</latitude>
         <longitude>23.47298</longitude>
       </geo-location>
     </locatable-item>
     <locatable-item>
       <name>Reference Frame Only</name>
       <geo-location>
         <reference-frame>
           <astronomical-body>moon</astronomical-body>
           <geodetic-system>
             <geodetic-datum>me</geodetic-datum>
           </geodetic-system>
         </reference-frame>
       </geo-location>
     </locatable-item>
   </locatable-items>
   </ns0:config>

              Figure 4: 3: Example XML data of geo location use.

Appendix B.  Acknowledgements

   We would like to thank Jim Biard and Ben Koziol for their reviews and
   suggested improvements.  We would also like to thank Peter Lothberg
   for the motivation as well as help in defining a more broadly useful
   geographic location object.

   We would also like to thank object, and Acee Lindem and Qin Wu for their work
   on a geographic location object that led to this documents creation.

Author's Address
   Christian Hopps
   LabN Consulting, L.L.C.

   Email: chopps@chopps.org