further explanations to limit SAX output

Doc/course.xml

@@ -7908,11 +7908,56 @@ Subject: Firewall problems</programlisting>
                     int,int)</code> may be used to print the desired output.
                     But you have to limit this output to <tag
                     class="starttag">from</tag> and <tag
-                    class="starttag">subject</tag> elements. This can be
-                    achieved by introducing boolean variables being set to
-                    true or false inside your startElement and endElement
-                    methods accordingly to keep track of your current event
-                    state.</para>
+                    class="starttag">subject</tag> elements. Taking the <tag
+                    class="starttag">subject</tag>Firewall problems<tag
+                    class="endtag">subject</tag> element as an example the
+                    corresponding event sequence reads:</para>
+
+                    <informaltable border="1">
+                      <tr>
+                        <th>Event</th>
+
+                        <th>Corresponding callback</th>
+                      </tr>
+
+                      <tr>
+                        <td>...</td>
+
+                        <td>...</td>
+                      </tr>
+
+                      <tr>
+                        <td>Opening <tag class="starttag">subject</tag>
+                        element</td>
+
+                        <td>startElement(...)</td>
+                      </tr>
+
+                      <tr>
+                        <td>Firewall problems</td>
+
+                        <td>characters(...)</td>
+                      </tr>
+
+                      <tr>
+                        <td>Closing <tag class="endtag">subject</tag>
+                        element</td>
+
+                        <td>endElement(...)</td>
+                      </tr>
+
+                      <tr>
+                        <td>...</td>
+
+                        <td>...</td>
+                      </tr>
+                    </informaltable>
+
+                    <para>Limiting output of our characters(...) callback
+                    method can be achieved by introducing instance scope
+                    boolean variables being set to true or false inside your
+                    startElement(...) and endElement(...) methods accordingly
+                    to keep track of the current event state.</para>
                   </question>
                   <answer>