The Time Zone Data Distribution Service (TZDIST) Geolocate Extension
draft-murchison-tzdist-geolocate-00

Abstract

This document defines an extension to the Time Zone Data Distribution Service (RFC 7808) to allow a client to determine the correct time zone for a geographic point location using a 'geo' URI (RFC 5870).

Open Issues

• Does the 'geo' URI value have to be percent-encoded?
• Should we advertise the supported coordinate reference systems (and if so, how?) or simply mandate crs=wgs84?
• Should we discuss territorial and/or international waters?
• What, if any, additional security and privacy concerns are introduced by this extension?

Status of This Memo

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This Internet-Draft will expire on April 17, 2017.

Copyright Notice

Copyright (c) 2016 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Table of Contents

• 1. Introduction
• 2. Conventions Used in This Document
• 3. "geolocate" Action
• 3.1. Examples: geolocate action
• 4. Security Considerations
• 5. Privacy Considerations
• 6. IANA Considerations
• 6.1. Service Action Registration
• 6.2. Registration of invalid-location Error URN
• 7. Acknowledgments
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Author's Address

1. Introduction

Clients using a Time Zone Data Distribution Service (TZDIST), particularly mobile clients, may not have prior knowledge of which time zone is appropriate for a particular geographic region. This specification defines a new TZDIST service action to allow a client to query a server with a geographic point location and have that server determine if the location lies within the boundaries of an existing time zone and return the corresponding time zone identifiers.

This specification does not define the source of the time zone boundary data. It is assumed that a reliable and accurate source is available. Two such sources are [TZSHAPE] and [TZBB].

2. Conventions Used in This Document

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].

3. "geolocate" Action

Name:

gelocate

Request-URI Template:

{/service-prefix,data-prefix}/zones{?location}

Description:

This action allows a client to query the time zone data distribution service for the time zone identifier corresponding to the given geographic point location, specified as a 'geo' URI [RFC5870].

If the 'geo' URI specifies an uncertainty value (";u=" parameter), the server MUST return the time zone identifiers for all time zones whose boundary passes through the radius of uncertainty. In the absence of a client-supplied uncertainty value, the server MAY use an implicit uncertainty to coincide with any uncertainty in the time zone boundary data that it uses.

If the 'geo' URI specifies a coordinate reference system (";crs=" parameter) that is unsupported by the server, the server SHOULD return a JSON "problem details" object [RFC7807] in the response body including a "type" member with an "invalid-location" error URN as defined below.

Parameters:

location=<geo-URI>

REQUIRED, and MUST occur only once.

Response:

The response has the same format as the "list" and "find" actions (see [RFC7808] Section 6.2), with one result object for each geolocated time zone. If for any reason the server can not determine a time zone in which the point is located (e.g. uninhabited location), it MUST return a "list" response containing zero time zone objects.

Possible Error Codes

urn:ietf:params:tzdist:error:invalid-location

The "location" URI query parameter is missing, has an incorrect/unsupported value, or appears more than once.

3.1. Examples: geolocate action

The examples below presume that the timezone context path has been discovered (see [RFC7808] Section 4.2.1) to be "/tzdist".

In this example the client asks for the time zone corresponding to Carnegie Mellon University.

>> Request <<

GET /tzdist/zones?location=geo:40.44388,-79.94199 HTTP/1.1
Host: tz.example.com

>> Response <<

HTTP/1.1 200 OK
Date: Fri, 30 Sep 2016 12:28:03 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx

{
  "synctoken": "890939292-1466089793",
  "timezones": [
    {
      "tzid": "America/New_York",
      "etag": "6602582-1466089793",
      "last-modified": "2016-06-16T15:09:53Z",
      "publisher": "IANA Time Zone Database",
      "version": "2016e",
      "aliases": [
        "US/Eastern"
      ]
    }
  ]
}

In this example the client asks for the timezone corresponding to the Hoover Dam with an uncertainty of 25m. Note that the dam straddles the Nevada/Arizona state line and therefore a time zone boundary.

>> Request <<

GET /tzdist/zones?location=geo:36.01596,-114.73748;u=25 HTTP/1.1
Host: tz.example.com

>> Response <<

HTTP/1.1 200 OK
Date: Fri, 30 Sep 2016 12:28:03 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx

{
  "synctoken": "890939292-1466089793",
  "timezones": [
    {
      "tzid": "America/Los_Angeles",
      "etag": "52807330-1466089793",
      "last-modified": "2016-06-16T15:09:53Z",
      "publisher": "IANA Time Zone Database",
      "version": "2016e",
      "aliases": [
        "US/Pacific"
      ]
    },
    {
      "tzid": "America/Phoenix",
      "etag": "3297940-1466089793",
      "last-modified": "2016-06-16T15:09:53Z",
      "publisher": "IANA Time Zone Database",
      "version": "2016e",
      "aliases": [
        "US/Arizona"
      ]
    }
  ]
}

4. Security Considerations

This specification does not introduce any additional security concerns beyond those described in [RFC7808]

5. Privacy Considerations

This specification does not introduce any additional privacy concerns beyond those described in [RFC7808].

6. IANA Considerations

6.1. Service Action Registration

This document defines the following new TZDIST Service Action to be added to the registry defined in Section 10.3.1 of [RFC7808]:

6.2. Registration of invalid-location Error URN

This section registers the "urn:ietf:params:tzdist:error:invalid-location" URN in the "TZDIST Identifiers" registry defined in Section 10.4 of [RFC7808].

URN:

urn:ietf:params:tzdist:error:invalid-location

Specification:

RFCXXXX, Section 3

Repository:

http://www.iana.org/assignments/tzdist-identifiers.

Contact:

IESG <iesg@ietf.org>

Index value:

N/A.

7. Acknowledgments

The author would like to thank the following individuals for contributing their ideas and support for writing this specification: Cyrus Daboo.

8. References

8.1. Normative References

8.2. Informative References

Author's Address