--- a/model/prov-n.html	Tue Jul 03 17:19:03 2012 +0100
+++ b/model/prov-n.html	Tue Jul 03 17:26:36 2012 +0100
@@ -2467,13 +2467,13 @@
 <section id="extensibility">
 <h4>Extensibility</h4>
 
-<p>The PROV data model is extensible by means of attributes <span class="name">prov:type</span> and <span class="name">prov:role</span>, allowing subtyping of expressions.  For some applications, novel  syntax may be convenient. Hence, the normative requirements are as follow.
+<p>The PROV data model is extensible by means of attributes <span class="name">prov:type</span> and <span class="name">prov:role</span> allowing subtyping of expressions.  For some applications, novel  syntax may also be convenient. Hence, the normative requirements are as follow.
 <ul>
 <li> PROV-N compliant parsers MUST be able to parse expressions matching the <code class="content"><a class="grammarRef"
- href="#prod-extensibilityExpression">extensibilityExpression</a></code> production.
-<li> As PROV provides no interpretation for these expressions, PROV compliant implementations 
+ href="#prod-extensibilityExpression">extensibilityExpression</a></code> production defined below.
+<li> As PROV provides no definition for these expressions, PROV compliant implementations 
  MAY ignore these expressions.</li>
-<li> Extensions to PROV and PROV-N MAY specify more specific productions and interpretations for these expressions. </li>
+<li> Extensions to PROV and PROV-N MAY specify more specific productions and interpretations for these expressions, which applications MAY adopt to follow. </li>
 </ul>
 </p>
 
@@ -2481,13 +2481,22 @@
 
 <tbody class="grammar-ref" data-ref="prod-extensibilityExpression"></tbody>
 <tbody class="grammar-ref" data-ref="prod-extensibilityArgument"></tbody>
-<tbody class="grammar-ref" data-ref="prod-extensibilityRecord"></tbody>
+<tbody class="grammar-ref" data-ref="prod-extensibilityTuple"></tbody>
 
 </table>
 
 <p>Expressions compatible with the
 <code class="content"><a class="grammarRef"
- href="#prod-extensibilityExpression">extensibilityExpression</a></code> production
+ href="#prod-extensibilityExpression">extensibilityExpression</a></code> production follow a general form of functional syntax, in which the predicate MUST be a
+<code class="content"><a class="grammarRef" href="#prod-QUALIFIED_NAME">qualifiedName</a></code>
+with a non-empty <code class="content"><a class="grammarRef" href="http://www.w3.org/TR/rdf-sparql-query/#rPN_PREFIX">prefix</a></code>.</p>
+
+
+
+<div class="anexample">
+<p>
+TODO: an example of extended syntax.</p>
+</div>