Merge pull request #781 from w3c/bp-edit-jtandy2

Added note about why w3cgeo:SpatialThing doesn't fit our need

bp/index.html

@@ -911,6 +911,17 @@ <h2>Spatial Things, Features and Geometry</h2>
       </div>
 
       <p>We say that the <a>spatial thing</a> is disjoint from the geometry object. The <a>spatial thing</a>, Eddystone Lighthouse (<a href="https://www.trinityhouse.co.uk/lighthouses-and-lightvessels/eddystone-lighthouse"><code>https://www.trinityhouse.co.uk/lighthouses-and-lightvessels/eddystone-lighthouse</code></a>), is the “real world phenomenon” about which we want to state facts (such as the height of its light is 41 meters above sea level) and link to other real world phenomena (for example, that it is located at Eddystone Rocks, Cornwall; another <a>spatial thing</a> identified as <a href="http://sws.geonames.org/2650253/"><code>http://sws.geonames.org/2650253/</code></a> by <a href="http://www.geonames.org">GeoNames</a>).</p>
+
+      <div class="note">
+        <p>Although we have borrowed the description of <a>spatial thing</a> from [[W3C-BASIC-GEO]], the formal RDFS definition of <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a> doesn't quite suit our purpose as there is the potential for confusion about whether it is <em>disjoint</em> from geometry. The definition of <a href="http://www.opengis.net/ont/geosparql#Feature"><code>geosparql:Feature</code></a>, which is derived from the [[ISO-19109]] definition of <a>Feature</a>, is a better semantic fit for <a>spatial thing</a> as it is explicity specified as being disjoint from <a href="http://www.opengis.net/ont/geosparql#Geometry"><code>geosparql:Geometry</code></a>.</p>
+
+        <p>First, the domain of <a href="http://www.w3.org/2003/01/geo/wgs84_pos#lat"><code>w3cgeo:lat</code></a>, <a href="http://www.w3.org/2003/01/geo/wgs84_pos#lon"><code>w3cgeo:lon</code></a> and <a href="http://www.w3.org/2003/01/geo/wgs84_pos#alt"><code>w3cgeo:alt</code></a> properties is <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a>. While one could interpret these properties as mapping to a geometry, as <a href="http://www.georss.org/simple">GeoRSS Simple</a> does, there isn't conclusive evidence that this is what was intended. Second, <a href="http://www.w3.org/2003/01/geo/wgs84_pos#Point"><code>w3cgeo:Point</code></a> is defined as a sub-class of <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a>. As a result, we have inconsistency in how <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a> may be interpretted. For example:</p>
+        <ul>
+          <li>Because a <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a> has lat/lon, some people might equate <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a> with <a href="http://www.opengis.net/ont/geosparql#Geometry"><code>geosparql:Geometry</code></a>;</li>
+          <li>Because the <a href="http://xmlns.com/foaf/0.1/Person"><code>foaf:Person</code></a> is defined as a sub-class of <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a>, some other people find it natural to equate <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a> with <a href="http://www.opengis.net/ont/geosparql#Feature"><code>geosparql:Feature</code></a></li>
+        </ul>
+        <p>So in summary, it's safer to say that our <a>spatial thing</a> equates to <a href="http://www.opengis.net/ont/geosparql#Feature"><code>geosparql:Feature</code></a>, and that it is <strong>not</strong> the same as <a href="http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"><code>w3cgeo:SpatialThing</code></a>.</p>
+      </div>
     </section>
 
     <section id="coverages">