--- a/model/prov-constraints.html	Thu Jun 07 09:53:00 2012 +0100
+++ b/model/prov-constraints.html	Thu Jun 07 10:58:38 2012 +0100
@@ -2046,7 +2046,10 @@
   
 <h4>Collections and Contents</h4>
 
-<p>We model the contents of a dictionary <span class="name">d</span> with a function contents, which can have the possible values:
+<p>We model the contents of a dictionary  with a function contents that has the following signature
+ Dictionary x Value -> Entity U {&#8869,?}.</p>
+
+<p>Given a dictionary <span class="name">d</span>, a value <span class="name">k</span>, contents is interpreted as follows:</p>
 <ul>
 <li>contents(d,<em>k</em>)=<em>e</em>:  there is an entry with key <em>k</em> and entity <em>e</em> in <span class="name">d</span>;
 <li>contents(d,<em>k</em>)=&#8869:  there is no entry with key <em>k</em> in <span class="name">d</span>;