draft-daviel-html-geo-tag-03
INTERNET-DRAFT Vancouver Webpages
<draft-daviel-html-geo-tag-03.txt> Sept 2000 (Expires Mar. 2001)
Geographic registration of HTML documents
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
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Abstract
This memo describes a method of registering HTML documents with a
specific geographic location through means of embedded META tags. The
content of the META tags gives the geographic position of the
resource described by the HTML document in terms of Longitude,
Latitude and optionally Elevation in a simple, machine-readable
manner. This information may be used for automated resource discovery
by means of an HTML indexing agent or search engine.
1. Introduction
Many resources described by HTML documents on the World-Wide-Web are
associated with a particular place on the Earth's surface. While
resource discovery on the Web has thus far focussed on document title
and open-text keyword searching, in these cases it may be beneficial
to facilitate geographic searching. Examples of this kind of resource
include pages describing restaurants, shipwrecks, wildlife refuges
etc.
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2. Coordinate Systems
Resource positions on the Earth's surface should be expressed in
degrees North of Latitude, degrees East of Longitude as signed
decimal numbers. Elevation should be expressed as a signed decimal
number of metres above datum. The number of decimal places given
should reflect the precision of the coordinates, with zeroes being
used as placeholders. A decimal point is optional where the
precision is less than one degree. Where the precision of the
coordinates is such that the datum used is significant, typically
more precise than one kilometre distance, positions should be
converted to the WGS 84 datum [3]. Elevations, if given, should be in
metres above datum. Positions given by a GPS set [4] with datum set
to "WGS 84" will in most cases be adequate, of the order of 15 metres
accuracy (with SA off).
3. Implementation
HTML markup should be added to the document in the form of a META
statement. This should be placed in the document head in accordance
with the HTML 4 specification [1]. The identifier "geo.position" is
used for Latitude, Longitude and optionally Elevation data. The
identifier "geo.placename" is used for a free text representation of
the position, for example "city, province" or "town, county, state".
The identifier "geo.region" is used for the country subdivision code
from ISO 3166-2 [10].
For resources within the United States and Canada, the "geo.region"
identifier as given by ISO 3166-2 is typically constructed from the
2-character country code [5] as used in Internet domain names, and
the common 2-character State/Province codes [8][9], joined with a
hyphen, for example "CA-BC" for British Columbia, Canada.
Where the official subdivision code is unknown, the 2-character
country code alone may be used in "geo.region", for example "DE" for
Germany.
It is anticipated that the "geo.placename" tag be used for resource
recognition, rather than resource discovery, due to possible
ambiguities in naming convention, language, word ordering and
placename duplicates.
Although the HTML specification [1] states that the name field is in
general case-sensitive, these "geo" tags should be recognized by
compliant agents regardless of case. Coordinates should be ordered
(Latitude ; Longitude) as for RFC 2426, RFC 2445 (vCard and iCal
specifications) [6][7]. If elevation is given, coordinates should be
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ordered (Latitude ; Longitude ; Elevation). (This is at variance
with common GIS practice, but better matches the intended audience of
this Draft.)
The Metadata Profile "http://geotags.com/geo" may be used as defined
in [1] to define the geo tag properties.
4. Examples
<HEAD profile="http://geotags.com/geo">
<META name="geo.position" content="48.54;-123.84;115">
describes a resource 115 metres above datum at position 48.54 degrees
North, 123.84 degrees West, while
<META name="geo.position" content="-10;60">
describes a resource at position 10 degrees South, 60 degrees East.
<META name="geo.placename" content="London, Ont">
<META name="geo.region" content="CA-ON">
describes a resource in London, Ontario, Canada, while
<META name="geo.placename" content="London">
<META name="geo.region" content="GB">
describes a resource in London, England (Great Britain).
The HTML attributes "lang", "dir" may be used to define the language
and directionality for the "geo.placename" tag as defined in [1], for
instance
<META name="geo.placename" lang="fr" content="Londres">
5. Applicability
As stated in the introduction, certain HTML documents may be
associated with a geographic position, while other documents are not.
For proper use of the "geo" tags as described in this draft, the
resource described in an HTML document should be associated with a
particular location for the lifetime of the document. The tags may
be properly used to describe, for instance, a retail store, a
mountain peak or a railway station but not a multinational company,
river, aircraft or mathematical theory.
The geographic position given is associated with the resource
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described by the HTML document, not with the physical location of the
document [2], or the location of the company responsible for
publishing or hosting the document. Thus, in some cases the country
code used in "geo.position" may differ from the country code forming
part of the host address in the document URL.
6. Further information
Further information may be obtained at http://geotags.com/geo
7. Security Considerations
This draft raises no security issues.
8. Internationalization considerations
The "geo.placename" tag content is free text, and should obey the
internationalization rules of HTML 4. "lang" and "dir" modifiers may
be used to specify the language of the content. Multiple instances of
geo.placename may be used with different "lang" modifiers.
Geo.placename content is coded using the character set of the
containing document.
Geo.position and geo.region tag content should use US-ASCII or UTF-8.
9. References
[1] Raggett, Le Hors, Jacobs, "HTML 4.0 Specification",
http://www.w3.org/TR/1998/REC-html40-19980424 , W3C, April 1998
[2] Davis et al., "A Means for Expressing Location Information in
the Domain Name System", RFC 1876, January 1996
http://www.alternic.org/rfcs/rfc1800/rfc1876.txt
[3] United States Department of Defense; DoD WGS-1984 - Its
Definition and Relationships with Local Geodetic Systems;
Washington, D.C.; 1985; Report AD-A188 815 DMA; 6127; 7-R-
138-R; CV, KV;
[4] ARINC Research Corporation, "Navstar GPS Space Segment /
Navigation User Interfaces", IRN-200C-002, September 1997
[5] International Organization For Standardization / Organisation
Internationale De Normalisation (ISO), "Standard ISO
3166-1:1997: Codes for the Representation of Names of
Countries and their subdivisions -- Part 1: Country codes",
1997.
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[6] Dawson & Stenerson, Internet Calendaring and Scheduling Core
Object Specification (iCalendar), RFC 2445, November 1998
http://www.alternic.org/rfcs/rfc2400/rfc2445.txt
[7] Dawson & Howes, vCard MIME Directory Profile, RFC 2426,
September 1998
http://www.alternic.org/rfcs/rfc2400/rfc2426.txt
[8] United States Postal Service, Official Abbreviations -
States and Possessions,
http://www.usps.gov/ncsc/lookups/abbr_state.txt
[9] Canada Post, the Postal Code, two-letter abbreviations,
http://www.canadapost.ca/CPC2/addrm/addrguide/prov_symbols.html
[10] International Organization For Standardization / Organisation
Internationale De Normalisation (ISO), "Standard ISO
3166-2:1998: Codes for the Representation of Names of Countries
and their subdivisions -- Part 2: Country subdivision code",
1998.
10. Author's Address
Andrew Daviel
Vancouver Webpages, Box 357
185-9040 Blundell Rd
Richmond BC
V6Y 1K3
Canada
Tel. (604)-377-4796
Fax. (604)-270-8285
andrew@vancouver-webpages.com
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