--- a/model/ProvenanceModel.html	Fri Sep 16 00:17:37 2011 +0100
+++ b/model/ProvenanceModel.html	Fri Sep 16 09:27:47 2011 +0100
@@ -2082,9 +2082,29 @@
     <section id="extensibility-section"> 
 <h2>PROV-DM Extensibility Points</h2>
 
-<div class='note'>Summarize here the extensibility points of PROV-DM.
-Attributes, annotations, namespaces. Predefined attributes: prov:type.</div>
-
+
+<p>The PROV data model provides several extensibility points that allow designers to specialize it to specific applications or domains. We summarize these extensibility points here:
+
+<ul>
+<li> Attributes are constructs of the data model that allow representations of aspects of the world's things and activities to be expressed.  Applications are free to introduce application-specific attributes, according to their perspective on the world.  Attributes for a given application can be distinguished by qualifying them with a prefix denoting a namespace declared in a namespace declaration.
+
+<p>The PROV DM namespace (TBD) declares a set of reserved attributes: <tt>type</tt>, <tt>location</tt>.</li>
+
+<li>Annotation expressions allow arbitrary metadata to be associated with identifiable expressions of PROV-DM. Annotation expressions consist of name-value pairs. Like attributes, names are qualified by a namespace.</li>
+
+<li>Use, generation, and control qualifiers offer a mechanism to
+describe modal aspects of use, generation, and control expressions.  
+They consist of ordered sequence of name-value pairs. Such names
+are also qualified by a namespace.</li>
+
+<li>Namespaces allow attributes and names to be qualified. </li>
+
+<li>Domain specific values can be expressed by means of typed literals. </li>
+</ul>
+
+<p>The PROV data model is designed to be application and technology independent, but specializations of PROV-DM are welcome and encouraged.  To ensure inter-operability, specializations of the PROV data model that exploit the extensibility points summarized in this section MUST preserve the semantics specified in this document. For instance, a qualified attribute on a domain specific entity expression MUST represent an aspect of a characterized thing and this aspect MUST remain unchanged during the characterization's interval of this entity expression.</p>
+
+</p>
 
     </section>