--- a/model/prov-dm-constraints.html	Mon Apr 02 09:44:00 2012 +0100
+++ b/model/prov-dm-constraints.html	Mon Apr 02 09:56:27 2012 +0100
@@ -680,9 +680,28 @@
 
 <section id="term-Start">
 <h3>Start</h3>
+
+
+<p>An <a>activity start event</a> is the <a title="event">instantaneous event</a> that marks the instant an activity starts. It allows for an optional time attribute.  Activities also allow for an optional start time attribute.  If both are specified, they MUST be the same, as expressed by the following constraint.
+</p>
+
+<div class='constraint' id='unique-startTime'>
+Given an activity <span class="name">activity(a,t1,t2,attr1)</span> and its start <span class="name">wasStartedBy(id,a,e,t,attrs)</span>,  then <span class="name">t</span>=<span class="name">t1</span>.
+</div> 
 </section> 
+
 <section id="term-End">
 <h3>End</h3>
+
+
+<p>An <a>activity end event</a> is the <a title="event">instantaneous event</a> that marks the instant an activity ends. It allows for an optional time attribute.  Activities also allow for an optional end time attribute.  If both are specified, they MUST be the same, as expressed by the following constraint.
+</p>
+
+<div class='constraint' id='unique-endTime'>
+Given an activity <span class="name">activity(a,t1,t2,attr1)</span> and its end <span class="name">wasEndedBy(id,a,e,t,attrs)</span>,  then <span class="name">t</span>=<span class="name">t2</span>.
+</div> 
+
+
 </section>