--- a/model/prov-constraints.html	Tue Jul 10 09:34:55 2012 -0400
+++ b/model/prov-constraints.html	Tue Jul 10 14:40:04 2012 +0100
@@ -1030,7 +1030,7 @@
         <div class='inference' id="specialization-irreflexive">
 <p>
     For any entity <span class='name'>e</span>, it is not the case that
-    have <span class='name'>specializationOf(e,e)</span>.</p>
+<span class='name'>specializationOf(e,e)</span> holds.</p>
     </div>
 
 <p>
@@ -1926,7 +1926,7 @@
   validity checking</div>
 
   We define a
-notion of <a>normalization</a>, <a>validity</a> and <a>equivalence</a> of PROV instancess.  Equivalence has the following characteristics:
+notion of <a>normalization</a>, <a>validity</a> and <a>equivalence</a> of PROV instances.  Equivalence has the following characteristics:
 
 
 <ul>
@@ -1961,15 +1961,24 @@
 <div id="optional-attributes1">
 <p>PROV-N allows some statement parameters and attributes to
   be optional. Unless otherwise specified, when an
-  optional attribute is not present in a statement, some value
-  SHOULD be inferred for this attribute.</p>
+  optional attribute is not present in a statement, it has a default
+  value.</p>
 
-  The only exception is:
+  The only exceptions are:
   <ul>
 <li><div id="optional-attributes4">In an association of the form
-  <span class="name">wasAssociatedWith(a, ag,-,attr)</span>, the
+  <span class="name">wasAssociatedWith(id;a, ag,-,attr)</span>, the
   absence of a plan means: either no plan exists, or a plan exists but
-  it is not identified.</div></li>
+  it is not identified.  Thus, it is not equivalent to <span
+  class="name">wasAssociatedWith(id;a, ag,p,attr)</span> where a
+  plan <span class="name">p</span> is given.</div></li>
+  <li><div id="optional-attributes4">In an association of the form
+  <span class="name">wasDerivedFrom(id;e1, a,e2,attr)</span>, the
+  absence of the optional activity, generation and use identifiers
+  means that the derivation relationship may encompass multiple activities,
+generations, and uses.  Thus, it is not equivalent to <span
+  class="name">wasDerivedFrom(id;e1,e2,a,g,u,attr)</span> where some
+  activity, generation and use are given explicitly.</div></li>
 </div></li>
    </ul>
 </div>