--- a/model/prov-constraints.html	Wed Aug 08 17:31:09 2012 +0100
+++ b/model/prov-constraints.html	Wed Aug 08 18:25:24 2012 +0100
@@ -1786,9 +1786,7 @@
 <p>
   <span class='conditional'>IF</span> <span
   class="name">wasDerivedFrom(_id; e2,e1,_a,_g,_u,[prov:type='prov:Revision'])</span>, <span class='conditional'>THEN</span> <span
-  class="name">alternateOf(e2,e1)</span>.  The activity <span class="name">_a</span>,
-  generation <span class="name">_g</span>,
-  or use <span class="name">_u</span> may be the placeholder <span class="name">-</span>.
+  class="name">alternateOf(e2,e1)</span>.  
 </p>
 <!--
 <li><span class='conditional'>IF</span> <span
@@ -2847,9 +2845,12 @@
 
 <div class='constraint'
   id='derivation-generation-generation-ordering'>
+  <p>
+In this constraint, any <span class="name">_a</span>, <span
+  class="name">_g</span>, <span class="name">_u</span> MAY be placeholders.</p>
 <p>
  <span class="conditional">IF</span>
-<span class="name">wasDerivedFrom(_d; e2,e1,-,-,-,attrs)</span>
+<span class="name">wasDerivedFrom(_d; e2,e1,_a,_g,_u,attrs)</span>
   and
 <span class="name">wasGeneratedBy(gen1; e1,_a1,_t1,_attrs1)</span>
   and
@@ -3163,7 +3164,12 @@
 <span class="math">I</span> is invalid).
 
 
-
+<hr />
+
+  <div class="note">
+    @TODO: Add constraint to the effect that in a normal form,
+    wasDerivedFrom(e1,e2,-,g,u) is only legal if g and u are also "-".
+    </div>
     
 <hr />
 
@@ -3419,7 +3425,8 @@
 <span class='conditional'>THEN</span> 
 <span class="name">'activity' &isin; typeOf(a)</span> AND
 <span class="name">'agent' &isin; typeOf(ag)</span> AND
-<span class="name">'entity' &isin; typeOf(pl)</span>.
+<span class="name">'entity' &isin; typeOf(pl)</span>.  In this
+constraint, <span class="name">pl</span> MUST NOT be a placeholder.
 
 <li>
 <span class='conditional'>IF</span>