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<!--#set var="title" value="GeoRSS in RDF"-->
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html">
<title>GeoRSS in RDF</title>
<link href='http://fonts.googleapis.com/css?family=Open+Sans' rel='stylesheet' type='text/css'><link href="global.css" type="text/css" rel="stylesheet">
</head>
<body>
<div class="nav"><a href="index.html">home</a> | <a href="overview.html">overview</a> | <a href="model.html">model</a> | <a href="gml.html">gml</a> | <a href="simple.html">simple</a> | <a href="w3c.html">W3C Geo</a> | <a href="atom.html">atom</a> | <a href="rdf_rss1.html">rdf/rss1</a> | <a href="implementations.html">implementations</a> | <a href="proposals.html">proposals</a></div>
<h4>GeoRSS ::<br/>Geographically Encoded Objects for RSS feeds</h4>
<h2>GeoRSS in RDF</h2>
<h3>RDF: a quick introduction</h3>
<p><i>This material is preliminary and only for discussion at this time. </i></p>
</p>
<p>
The RDF data model is so simple that it can be explained in a few paragraphs.</p>
RDF encodes information using statements of the form
"the object O has property P with value V". The value of a property may be a literal value,
such as a string or number, or another object. Properties and objects are usually named using URIs.
Here is an example:</p>
<p>
<pre style="z-index: 3;">
the Object http://en.wikipedia.org/wiki/Astoria_Oregon has
the Property http://www.georss.org/georss/point with value
"46.183 -123.816".
</pre>
</p>
<p>This statement means that the geographical location associated
with the specified Wikipedia page has latitude 46.183 and longitude
-123.816. In this case, the object is a web page, but physical or conceptual
entities can also be named by URI in RDF statements.</p>
<p>
A unit of RDF content (eg an RDF page) is nothing more than a set of such statements.
If the objects and literals are construed as nodes, and the statements as edges,
the RDF data model can be viewed as a labeled directed graph. In particular, the statement
"A has property P with value B" is represented by an edge labeled P joining node
A to node B.
The detailed rules concerning labeling are: an edge is always labeled with a URI;
an object node may be unlabeled, or labeled with a URI; a literal node is labeled
with its value.
</p>
<p>
This simple data model has several serializations - several representations as linear
text. The most commonly used (and the most complicated) utilizes XML. In XML,
nodes and properties are represented by XML elements. The properties of a node element are its
children; each property element has a child, or content in the case of a literal,
representing the value of the property. For example:
</p>
<pre style="z-index: 3;">
<?xml version="1.0"?>
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:georss="http://www.georss.org/georss/">
<rdf:Description rdf:about="http://en.wikipedia.org/wiki/Astoria_Oregon">
<dc:title>Astoria, Oregon</dc:title>
<strong><georss:point>46.183 -123.816</georss:point></strong>
</rdf:Description>
</rdf:RDF>
</pre>
</p>
<p>For more information about RDF, see the <a href="http://www.w3.org/RDF">RDF</a> pages at W3C.</p>
<h3>Simple GeoRSS in RDF and RSS 1.0</h3>
<p>
In the RDF framework, the content and meaning of <a href="simple.html">Simple
GeoRSS</a> can be
stated in a few words:
<strong>georss:point, georss:line, georss:polygon, and georss:box</strong>
are RDF properties. Each has a string literal as value, with the detailed
forms as explained on the <a href="simple.html">Simple GeoRSS</a> page.
Asserting that the value of the property <strong>georss:point</strong> for an
object <strong>A</strong>
is <strong>"lat,long"</strong>
means that the geographical location with these coordinates is associated with <strong>A</strong>.
The nature of the association is left unspecified.
Similarly, the properties <strong>georss:line, georss:polygon,</strong> and<strong> georss:box</strong>,
assert the existence of associated
earth-located geometries.</p>
<p>
These properties can be used in any RDF context to make simple geographical assertions
about objects. Of particular interest in the current context is the RDF dialect
of RSS:
<a href="http://web.resource.org/rss/1.0/">RSS 1.0</a>. However, there is nothing
special about how GeoRSS properties are used in RSS 1.0 - we need only note that
any of the RSS 1.0 elements can be annotated with GeoRSS properties, including
rss:channel, rss:item, and rss:image. Here is an example:</p>
<pre style="z-index: 3;">
<rdf:RDF
xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
xmlns:dc='http://purl.org/dc/elements/1.1/'
xmlns='http://purl.org/rss/1.0/'
xmlns:georss="http://www.georss.org/georss/">
<channel rdf:about='http://www.xml.com/'>
<title>XML.com</title>
<link>http://www.xml.com/</link>
<description>XML.com Articles and Weblogs</description>
<dc:rights>Copyright 2005, O'Reilly Media, Inc.</dc:rights>
<items>
<rdf:Seq>
<rdf:li rdf:resource=
'http://www.oreillynet.com/pub/wlg/8466?CMP=OTC-TY3388567169' />
</rdf:Seq>
</items>
</channel>
<item rdf:about=
'http://www.oreillynet.com/pub/wlg/8466?CMP=OTC-TY3388567169'>
<title>Live Coverage XML 2005 (Tuesday Keynotes)</title>
<link>http://www.oreillynet.com/pub/wlg/8466?CMP=OTC-TY3388567169</link>
<description>
<![CDATA[A live look at the XML Keynotes and seminal talks.]]>
</description>
<dc:creator>Kurt Cagle</dc:creator>
<dc:date>2005-11-15T07:45:58-08:00</dc:date>
<strong><georss:point> 46.183 -123.816</georss:point></strong>
</item>
</rdf:RDF>
</pre>
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