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  <title>W3C Semantic Web Interest Group: Basic Geo (WGS84
  lat/long) Vocabulary</title>
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  <h1><a href="/2001/sw/interest/">W3C Semantic Web Interest Group</a></h1>

  <h2>Basic Geo (WGS84 lat/long) Vocabulary</h2>

  <p>Nearby in the Web: <a href=
  "http://esw.w3.org/topic/GeoInfo">ESW:GeoInfo wiki</a> | <a
href="http://del.icio.us/tag/geo">del.icio.us/tag/geo</a> |<a
href="http://locative.us/">locative.us</a> | <a
href="http://mappinghacks.com/">Mapping Hacks</a> | <a
href="http://www.schemaweb.info/schema/SchemaDetails.aspx?id=42">SchemaWeb entry</a>
</p>

  <p>Editor: <a href="/People/DanBri/">Dan Brickley</a>
  &lt;<a href="mailto:danbri@danbri.org">danbri@danbri.org</a>&gt; (SWIG Chair)</p>

  <p>This is a <em>basic</em> RDF vocabulary that provides the
  Semantic Web community with a namespace for representing
  <strong>lat</strong>(itude), <strong>long</strong>(itude) and
  other information about spatially-located things, using WGS84 as
  a reference datum.</p>

  <p>The vocabulary is getting significant usage, both (as intended)
  within RDF documents, but also as a namespace used within non-RDF XML
  documents, such as RSS 2.0 (<a href="#nonrdf">see below</a>).
</p>

<p>
The <a
href="http://locative.net/workshop/index.cgi?Locative_Packets">Locative
packets</a> format uses this vocabulary, as do Map Bureau's <a
href="http://www.mapbureau.com/rdfmapper/">RDF mapping</a> tools.
The <a href="http://geocoder.us/">geocoder.us</a> site, provides a free
geocoding service for the US, based on TIGER data, and accessible via
an <a href="http://geocoder.us/help/">RDF Web service</a> that uses this
vocabulary. Other applications include <a
href="http://blogmapper.com/#howloc">blogmapper</a> and <a
href="http://openguides.org/">openguides</a>. The <a
href="http://brainoff.com/worldkit/doc/rss.php">WordKit</a> system
also uses it for geocoding RSS 1.0 (ie. RDF), RSS 2.0 (non-RDF) and Atom
(non-RDF). The <a href="http://developer.yahoo.net/maps/">Yahoo!
Maps</a> service also makes use of this namespace, although
apparently only within a RSS 2.0 context. See the <a
href="http://esw.w3.org/topic/GeoInfo">ESW:GeoInfo</a> Wiki
entry for links to other uses of this work.
</p>


  <h2 id="status">Status of this Document</h2>

  <p>This document was created as an informal collaboration within
  W3C's <a href="/2001/sw/interest/">Semantic Web Interest
  Group</a>. This work is not currently on the W3C <a href=
  "http://www.w3.org/2004/02/Process-20040205/tr.html#Reports">recommendation
  track</a> for standardization, and has not been subject to the
  associated review process, quality assurance, etc. If there is
  interest amongst the W3C membership in standards work on a
  location/mapping RDF vocabulary, this current work may inform any
  more formal efforts to follow.</p>

  <h2 id="overview">Overview</h2>

  <p>This vocabulary begins an exploration of the
  possibilities of representing mapping/location data in RDF, and
  does not attempt to address many of the issues covered in the
  professional GIS world, notably by the <a href="http://www.opengeospatial.org/">Open Geospatial Consortium</a>
(OGC). Instead, we provide just a few basic terms that can be used in RDF (eg. <a
href="http://purl.org/rss/1.0/">RSS 1.0</a> or <a
href="http://xmlns.com/foaf/0.1/">FOAF</A> documents)
  when there is a need to describe latitudes and longitudes. The
motivation for using RDF as a carrier for lat/long info is RDF's
capability for cross-domain data mixing. We can describe not only
maps, but the entities that are positioned on the map. And we can use
any relevant RDF vocabularies to do so, without the need for expensive
pre-coordination, or for changes to a centrally maintained schema.
</p>


<!-- http://www.w3.org/2001/sw/Europe/graphics/tmbltext.html -->

  <h2 id="example">Examples</h2>

<p>A basic, standalone example:</p>

<pre>
&lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
        xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"&gt;
  &lt;geo:Point&gt;
    &lt;geo:lat&gt;55.701&lt;/geo:lat&gt;
    &lt;geo:long&gt;12.552&lt;/geo:long&gt;
  &lt;/geo:Point&gt;
&lt;/rdf:RDF&gt;

</pre>

<p>
An <a
href="http://www.w3.org/2001/sw/Europe/talks/200404-nict/slide6-2.html">example</a>
that combines Geo, <a href="http://www.dublincore.org/">Dublin Core</a>
and <a href="http://www.foaf-project.org/">FOAF</a> vocabularies:
</p>
<pre>
&lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
        xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
        xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"
        xmlns:dc="http://purl.org/dc/elements/1.1/"
        xmlns="http://xmlns.com/foaf/0.1/"&gt;
&lt;Person&gt;
 &lt;name&gt;Dan Brickley&lt;/name&gt;
 &lt;homepage dc:title="Dan's home page"
              rdf:resource="http://danbri.org/"/&gt;
 &lt;based_near geo:lat="51.47026" geo:long="-2.59466"/&gt;<span style="color: green;">
 &lt;rdfs:seeAlso rdf:resource="<a href="http://danbri.org/foaf.rdf">http:/danbri.org/foaf.rdf</a>"/&gt;</span>
 &lt;!-- more RDF here, using any RDF vocabularies --&gt;
&lt;/Person&gt;
&lt;/rdf:RDF&gt;
</pre>


<p>An example (from <a
href="http://brainoff.com/worldkit/doc/rss.php">WorldKit</a>) of
geo-coding with RSS 1.0:</p>

<div class="code">
&lt;?xml version="1.0"?&gt;<br/>
&lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
<span
style="color:red">xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"</span>
xmlns="http://purl.org/rss/1.0/"&gt;
<br/><br/>...<br/><br/>
&lt;item rdf:about="http://example.com/geo"&gt;<br/>
&nbsp;&lt;title&gt;An example annotation&lt;/title&gt;<br/>
&nbsp;&lt;link&gt;http://example.com/geo&lt;/link&gt;<br/>
&nbsp;&lt;description&gt;Just an example&lt;/description&gt;<br/>
<span style="color:red">&nbsp;&lt;geo:lat&gt;26.58&lt;/geo:lat&gt;<br/>
&nbsp;&lt;geo:long&gt;-97.83&lt;/geo:long&gt;<br/></span>
&lt;/item&gt;
<br/><br/>...<br/><br/>
&lt;/rdf:RDF&gt;
</div>


<!-- with an emphasis on representing WGS84 (world geodesic survey) -->
  <!--
<p>This document is a first-cut at providing some accompanying context
for the RDF vocabulary described below. Any supporting files can be accessed by
<a href="#files">browsing the file listings</a> provided below. </p> -->

  <h2 id="history">History</h2>

  <p>The origin of this workspace was the <a href=
  "http://rdfig.xmlhack.com/2003/01/09/2003-01-09.html#1042129747.716114">
  2003-01-09 discussion</a> in the RDF Interest Group <a href=
  "/RDF/Interest#irc">IRC channel</a>. We are taking a similar
  approach to the exploration of RDF vocabulary for calendars,
  although that work is more mature. See the <a href=
  "http://www.w3.org/2002/12/cal/">RDF Calendar Workspace</a> for
  more information.</p>

  <h2 id="vocabulary">Basic RDF Geo Vocabulary: Point/lat/long/alt</h2>

<p>See the <a
href="http://www.schemaweb.info/schema/SchemaInfo.aspx?id=42">SchemaWeb</a>
site for an overview of classes and properties, or the <a
href="http://www.w3.org/2003/01/geo/wgs84_pos#">underlying RDFS/OWL</a>
vocabulary description.</p>


  <p>Currently we specify only a very minimalistic RDF vocabulary
  for describing <strong>Point</strong>s with
  <strong>lat</strong>itude, <strong>long</strong>itude, and
  <strong>alt</strong>itude properties from the WGS84 reference
  datum specification.</p>

  <p>This design allows for basic information about points to be
  described in RDF/XML, and augmented with more sophisticated or
  application-specific metadata.</p>

  <p>The vocabulary also defines a property
  <strong>lat_long</strong>, but this should probably be removed,
  as few commentators have valued it.</p>

  <p>The vocabulary defines a class 'Point', whose members are
  points. Points can be described using the 'lat', 'long' and 'alt'
  properties, as well as with other RDF properties defined
  elsewhere. For example, we might use an externally defined
  property such as 'bornNear' or 'withinFiveMilesFrom', or perhaps
  other properties for representing lat/long/alt in non-WGS84
  systems.</p>

  <p>The 'lat' and 'long' properties take literal (ie. textual values),
  each in decimal degrees. The 'alt' property is decimal metres about
  local reference ellipsoid.</p>


  <h3>Design note: Datatyping and Whitespace</h3>

  <p>Whitespace in property values is insignificant, and
  discouraged. We do not use RDF's datatyping mechanism in the
  vocabulary's schema to note that the <code>rdfs:range</code> of
  the <code>lat</code>,<code>long</code> and <code>alt</code>
  properties are XML Schema <code>float</code> datatypes. Instead,
  from RDF's point of view, the properties are simply strings.</p>

  <p>This reduces the syntactic burden on RDF/XML documents using
  our vocabulary, since we write lat and long information as
  strings. The string representation of lat and long should follow
  the rules for XML Schema <code>float</code>, even though we do
  not indicate explicitly in RDF that we are representing floating
  point numbers. A future version of this document may be stricter
  about whitespace when marking up <code>float</code> values, so it
  is probably best to avoid any whitespace in your lat/long/alt
  markup.</p>

  <p>The semantics of the lat/long/alt properties are unaffected by
  xml:lang values, if present.</p>

<h3 id="nonrdf">Design note: non-RDF XML</h3>


<p>While it is quite possible to use the namespace in non-RDF XML
documents, developers should note that this reduces the availability of
such data within the <em>Semantic Web</em>, since specialist knowledge
of each XML tagset is needed before data can be safely interpreted. The
<a href="http://www.w3.org/TR/2004/NOTE-grddl-20040413/">GRDDL</a>
specification offers an XSLT-based mechanism for mapping such data
into RDF.
</p>


  <h2 id="discussion">Discussion</h2>

  <p>As this is an RDF vocabulary, we define properties of a kind
  of thing, a Point, rather than the structure and characteristics
  of an XML document type. XML Schemas and DTDs typically adopt the
  latter approach, and thus provide more guarantees about the
  information content of each document of some type. By contrast,
  our RDF vocabulary provides no guarantee about which things will
  be described in any particular RDF/XML document. For example, it
  may turn out that many point descriptions omit the altitude
  property, 'alt'. This doesn't make those documents
  <em>invalid</em> in any sense; they are merely less
  informative.</p>

  <p>We can note some rules for reasoning about the identity
  conditions for points. If we encounter a description of a
  <strong>Point</strong>, call it ?X, and another, call it ?Y, and
  ?X and ?Y have identical values for their 'lat' and 'long' and
  'alt' properties, we can conclude that ?X == ?Y, ie. that ?X and
  ?Y represent the self-same thing. Anything that has any 'lat',
  'long' or 'alt' properties will be a 'Point'. In our RDF Schema
  for the vocabulary, we indicate this using the rdfs:domain
  property.</p>

  <p>A <strong>Point</strong> has only one 'lat', only one 'long',
  and only one 'alt'; we could use W3C's Web Ontology Language
  (OWL) to express this. OWL allows us to note that these RDF
  properties are 'functional properties'.
  <!-- @@TODO: <em>does it?
or does OWL only allow this for non-datatype properties?</em> --></p>

  <h2 id="documents">Documents</h2>

  <ul>
    <li>An <a href="http://www.w3.org/2003/01/geo/wgs84_pos#">RDF
    vocabulary for WGS84 latitude/longitude/altitude markup</a>
    (namespace uri: <a href=
    "http://www.w3.org/2003/01/geo/wgs84_pos#">http://www.w3.org/2003/01/geo/wgs84_pos#</a>)</li>

    <li><a href=
    "http://rdfig.xmlhack.com/2003/01/10/2003-01-10.html#1042200521.031970">
    2003-01-10 #rdfig links</a>, including test data</li>

    <li><a href="http://www.w3.org/2003/01/geo/">SWIG Basic Geo (WGS84 lat/long) Vocabulary</a> (this document)</li>
  </ul>

  <h2 id="development">Development Plans</h2>

  <p>Regarding the <a href=
  "http://www.w3.org/2003/01/geo/wgs84_pos#">http://www.w3.org/2003/01/geo/wgs84_pos#</a>
  vocabulary: it is pretty simple and should hopefully stay that
  way, ie. short and simple enough to memorise and use. There may
  be some need to extend it, based on deployment experience, test
  cases etc. Time will tell.</p>

  <p>Interested SWIG members meet occasionally in the <a href=
  "irc://irc.freenode.net:6667/swig">#swig</a> IRC channel on
  FreeNode. The <a href=
  "http://ilrt.org/discovery/chatlogs/swig/">IRC logs</a> and
  <a href="http://swig.xmlhack.com/">weblogs</a> generally serve as
  meeting records. At the time of writing, no meetings are
  scheduled.</p>

  <p>For related work and further discussion and collaboration, see
  the <a href="http://esw.w3.org/topic/GeoInfo">GeoInfo</a> entry
  in the <a href="http://esw.w3.org/topic/FrontPage">ESW
  Wiki</a>.</p>
  <hr />

  <p>Contact: <a href="http://danbri.org/">Dan Brickley</a>
  &lt;<a href="mailto:danbri@danbri.org">danbri@danbri.org</a>&gt;</p>$Id:
  HEADER.html,v 1.38 2004/02/06 17:38:12 danbri Exp $

  <h4>recent changes</h4>
  <pre>
$Log: Overview.html,v $
Revision 1.21  2006/02/01 22:14:46  danbri
added a parag noting decimal degrees for lat and long; decimal metres above ellipsoid for alt

Revision 1.20  2005/07/08 18:22:34  danbri
A few more introductory words.

Revision 1.19  2005/07/08 18:14:35  danbri
added links to rss1, dublincore, foaf pages

Revision 1.18  2005/07/08 18:01:08  danbri
s/rdfig/swig/ somewhere i missed

Revision 1.17  2005/07/08 17:59:11  danbri
trimmed

Revision 1.16  2005/07/08 17:55:54  danbri
more links

Revision 1.15  2005/07/08 17:45:30  danbri
added geocoder link

Revision 1.14  2005/07/08 17:44:41  danbri
added geocoder link

Revision 1.13  2005/07/08 17:19:35  danbri
markup bug

Revision 1.12  2005/07/08 17:18:25  danbri
noted that 2nd eg uses DC too

Revision 1.11  2005/07/08 17:17:08  danbri
CSS

Revision 1.10  2005/07/08 17:14:35  danbri
CSS

Revision 1.9  2005/07/08 17:11:56  danbri
CSS

Revision 1.8  2005/07/08 17:11:06  danbri
CSS

Revision 1.7  2005/07/08 17:05:26  danbri
more examples

Revision 1.6  2005/07/08 16:55:36  danbri
tidying text

Revision 1.5  2005/07/08 16:54:25  danbri
moved nonrdf later into doc

Revision 1.4  2005/07/08 16:51:59  danbri
markup fixes

Revision 1.3  2005/07/08 16:50:41  danbri
more text, discussion of non-rdf xml, and links to apps

Revision 1.2  2005/07/08 16:33:23  danbri
added more navigation

Revision 1.1  2005/07/08 16:25:23  danbri
new writeup

Revision 1.38  2004/02/06 17:38:12  danbri
Fixed a bad commit screwup

Revision 1.36  2003/12/14 02:23:14  danbri
anchored

Revision 1.35  2003/12/14 02:19:29  danbri
anchored

Revision 1.34  2003/04/03 00:30:01  danbri
removed related links; linked to Wiki instead

Revision 1.33  2003/02/19 00:40:10  danbri
removed SuckyCaps from Grub[Ss]treet (even if it is WikiBased :)

Revision 1.32  2003/01/11 19:02:23  danbri
Updated datatypes section, now that datatyping has been removed from the
schema.

Revision 1.31  2003/01/11 12:27:52  danbri
Added link to 2.2M Danish addresses.

Revision 1.30  2003/01/11 12:09:12  danbri
Added Sean Palmer's work on computing distances in RDF, and his infomesh-geo schema.

Revision 1.29  2003/01/11 12:03:33  danbri
Added link to Sean Palmer's 'geo' URN proposal.

Revision 1.28  2003/01/11 11:19:58  danbri
Revised the note re whitespace to mention use of RDF datatyping, and
to discourage use of whitespace. This should be re-organised to separate the
two issues. Also noted need for clearer advice on the whitespace issue.

Revision 1.27  2003/01/11 10:57:40  danbri
Added final '#' to namespace uriref in one place that I missed yesterday.

Revision 1.26  2003/01/11 01:23:25  danbri
Added DAML Geofile data.

Revision 1.25  2003/01/10 23:05:49  danbri
Changed to say: *An* RDF Geo vocab... (there will doubtless be others).

Revision 1.24  2003/01/10 22:52:40  danbri
Fixed a bug in the identity reasoning section ('alt' was ommitted from
the identity rules).  Added a paragraph contrasting RDF and XML schema
systems.

Revision 1.23  2003/01/10 22:33:54  danbri
Added example snippet. Also Syndic8 Geo metadata maker.

Revision 1.22  2003/01/10 21:31:43  danbri
Swapped a couple of paragraphs around, fixed some markup bugs and added a comment
explaining the role of rdfs:domain.

Revision 1.21  2003/01/10 21:28:29  danbri
Re-organised the page, and added some more detailed description of the
Point/lat/long/alt design, mentioning identity rules for the Point class and
the possible use of OWL to clarify the design.

Revision 1.20  2003/01/10 19:53:43  danbri
Added DCMI Point Encoding Scheme.

Revision 1.19  2003/01/10 19:46:54  danbri
Adding final '#' to geo vocab namespace uriref, for consistency with schema.

Revision 1.18  2003/01/10 19:45:28  danbri
Added link to Syndic8 metadata spec.

Revision 1.17  2003/01/10 17:58:22  danbri
Added a link to GML 2.0, Simon Cox et al. for OGC., Feb 2001.

Revision 1.16  2003/01/10 17:50:22  danbri
Added Muxway links, from Joshua Schachter.

Revision 1.15  2003/01/10 17:45:20  danbri
Added @semantics link from Alberto.

Revision 1.14  2003/01/10 16:51:46  danbri
Added streetmap Perl module, and reference to xmethods.net web service
directory.

Revision 1.13  2003/01/10 16:43:03  danbri
Added GeoURL location/add yourself page, NVML and DCMI Box Encoding
Scheme.

Revision 1.12  2003/01/10 16:09:45  danbri
Added Spacenamespace sample data from Jo Walsh, and ptr to PostGIS docs.

Revision 1.11  2003/01/10 14:15:14  danbri
Noted that OSGB FAQ includes pointers to conversion code.

Revision 1.10  2003/01/10 14:13:05  danbri
Added Garmin, UK waypoints and OS links.

Revision 1.9  2003/01/10 12:50:21  danbri
added previous cvs history, so you can see how busy I've been...


revision 1.8
date: 2003/01/10 12:48:14;  author: danbri;  state: Exp;  lines: +8 -1
added blogmapper and rdfmap links

revision 1.7
date: 2003/01/10 12:42:05;  author: danbri;  state: Exp;  lines: +4 -1
added rdfmap

revision 1.6
date: 2003/01/10 12:37:16;  author: danbri;  state: Exp;  lines: +27 -8
added Status info

revision 1.5
date: 2003/01/10 12:30:23;  author: danbri;  state: Exp;  lines: +3 -1
added opengis consortium

revision 1.4
date: 2003/01/10 11:59:03;  author: danbri;  state: Exp;  lines: +3 -2
fixed buglet in vocab, added more wgs links

revision 1.3
date: 2003/01/10 11:46:43;  author: danbri;  state: Exp;  lines: +4 -4
added more links

revision 1.2
date: 2003/01/10 11:40:50;  author: danbri;  state: Exp;  lines: +5 -5
added more links

revision 1.1
date: 2003/01/10 11:28:17;  author: danbri;  state: Exp;
first cut at contextual overview doc


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