RDF Interest Group J. Walsh Internet-Draft Category: Informational May 2004 <draft-walsh-wgs84-geopos-00.txt>
see: RDFIG geo workspace, wgs84_pos schema
$Revision: 0.1 $ of $Date: 2004/05/18 13:34:00 $
This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.
This document describes a vocabulary suitable for use in XML and RDF/XML documents for indicating points in space defined by the WGS84 geospatial reference system.
RDF [rdf] is a language designed to support the Semantic Web, by facilitating resource description and data exchange on the Web. RDF provides common structures that can be used for interoperable data exchange and follows the W3C design principles of interoperability, evolution, and decentralization.
WGS (World Geodesic Survey) 84 [wgs84] is a common geodetic reference system, including an earth model ellipsoid and geodetic datum. WGS 84 is used in GPS (global positioning) and civil aviation systems.
This document describes an RDF vocabulary for representing WGS84 (world geodesic survey) lat/long/alt positioning. The RDF schema corresponding to this vocaulary is at http://www.w3.org/2003/01/geo/wgs84_pos#
This document illustrates the representation of points in RDF/XML, and demonstrates the suitability of the vocabulary for inclusion as a payload in other internet standards dealing with presence of agents, such as geopriv PIDF [pidf] and foaf [foaf]. It is intended to provide a low-implementation-threshold alternative to GML [gml] for the simple description of geospatial positions.
A SpatialThing defined by this vocabulary is anything with spatial extent.
The vocabulary defines a class 'Point', whose members are points referenced to the WGS84 datum. A Point MUST have a 'lat' and a 'long' and MAY have an 'alt' .
A Point is a subclass of a SpatialThing.
The 'lat' property indicates a WGS84 latitude in decimal format.
A Point or other spatially referenced object MUST include a latitude property.
The 'long' property indicates a WGS84 longitude in decimal format.
A Point or other spatially referenced object MUST include a longitude property.
The 'alt' property indicates a WGS84 altitude in decimal format. Value for 'alt' is in metres above the WGS84 sphere.
A Point or SpatialThing MAY include an altitude property.
The wgs84_pos RDF schema does not use RDF's datatyping mechanism in the vocabulary's schema to note that the rdfs:range of the lat,long and alt properties are XML Schema [xsd] 'double' datatypes. Instead, from RDF's point of view, the properties are simply strings.
The string representation of lat and long SHOULD follow the rules for XML Schema float, even though we do not indicate explicitly in RDF that we are representing floating point numbers.
A point fragment for embedding in other XML or RDF/XML document types such as RSS1.0[rss] or PIDF[pidf]
<geo:Point geo:lat="54.5722" geo:long="0.014024"/>
A fully-formed RDF/XML document describing a point
<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#">
<geo:Point>
<geo:lat>54.5722</geo:lat>
<geo:long>0.014024</geo:long>
</geo:Point>
</rdf:RDF>
Jo Walsh
Unicorn Precinct XIII
306 Elsie Street
San Francisco, CA, US
mailto:jo@frot.org
http://locative.net/workshop/index.cgi?Jo_Walsh