--- a/rdf-primer/index.html	Tue Nov 12 01:02:00 2013 +0100
+++ b/rdf-primer/index.html	Tue Nov 12 12:52:18 2013 +0100
@@ -216,7 +216,7 @@
 
     <h2>RDF Data Model</h2>
 
-    <section id="subsection-statement">
+    <section id="subsection-triple">
 
     <h3>Triples</h3>
     
@@ -238,7 +238,6 @@
 
     <pre class="example">
       &lt;Bob&gt; &lt;is a&gt; &lt;person&gt;.
-      &lt;Alice&gt; &lt;is a&gt; &lt;person&gt;.
       &lt;Bob&gt; &lt;is a friend of&gt; &lt;Alice&gt;.
       &lt;Bob&gt; &lt;is born on&gt; &lt;the 4th of July 1990&gt;. 
       &lt;Bob&gt; &lt;is interested in&gt; &lt;the Mona Lisa&gt;.
@@ -451,7 +450,55 @@
     RDF. </p>
 
     <p>To support the definition of vocabularies RDF provides an RDF
-    Vocabulary Description Language called RDF-Schema [[!RDF-SCHEMA]].
+    Vocabulary Description Language called RDF-Schema
+    [[!RDF-SCHEMA]]. This allows you to define senabtuc cinstraints on
+    your RDF data. For example, you can state that
+    <code>ex:friendOf</code> is a predicate and that subject and
+    object of this property must be resources of class
+    </code>ex:Person</code>. <p>
+
+    <p>RDF Schema uses the noion of "class" to
+    model groups of resources that can act as subject or objects. The
+    term "property" is used to model predicates.  The main modelling
+    constructs in RDF Schema are listed in the Table below:
+
+<table border="1" id="table-rdf-schema">
+  <tbody>
+    <tr>
+      <th>RDF Schema construct</th>
+      <th>Description</th>
+    </tr>
+    <tr>
+      <td>rdfs:Class</td>
+      <td>The class of RDF classes.</td>
+    </tr>
+    <tr>
+      <td>rdf:Property</td>
+      <td>The class of RDF properties.</td>
+    </tr>
+    <tr>
+      <td>rdf:type</td>
+      <td>Subject (any resource) is an instance of object (a class)</td>
+    </tr>
+    <tr>
+      <td>rdfs:subClassOf</td>
+      <td>Subject (a class) is a subclass of object (a class)</td>
+    </tr>
+    <tr>
+      <td>rdfs:subPropertyOf</td>
+      <td>Subject (a property) is a subproperty of object (a property)</td>
+    </tr>
+    <tr>
+      <td>rdfs:domain</td>
+      <td>Domain of subject (a property) is object (a class)</td>
+    </tr>
+    <tr>
+      <td>rdfs:range</td>
+      <td>Range of subject (a property) is object (a class)</td>
+    </tr>
+  </tbody>
+  <caption>Main RDF Schema constructs</caption>
+</table>
     
 
     <p>@@ Discuss FOAF, Dublin Core, schema.org, SKOS and WordNet as typical examples</p>
@@ -599,7 +646,7 @@
 
     <h2>RDF Graphs and what you can do with them</h2>
 
-    <p></p>
+    <p>@@ example: derive that Alice is a person</p>
 
 </section>