--- a/model/working-copy/wd6-collections-constraints.html	Fri Jun 08 20:14:53 2012 +0100
+++ b/model/working-copy/wd6-collections-constraints.html	Fri Jun 08 20:22:51 2012 +0100
@@ -279,7 +279,7 @@
 
 The interpretation of Collection statements is defined by the following axioms. 
 
-Function Contents: C → ℘(E) maps a collection entity c ∈ C to a finite set {e1, … en} ⊂ ℘(E) of entities, where C is the set of all Entities of type Collection, and E  is the set of all Entities.
+Function Contents: C → ℘(E) maps a collection entity c ∈ C to a finite set {e1, … en} ⊂ E of entities, where C is the set of all Entities of type Collection, and E  is the set of all Entities.
 <ol>
 <li><span class="name">entity(c, [prov:type='prov:EmptyCollection'])</span> &rArr; Contents(c) = &empty;
 
@@ -304,13 +304,21 @@
 
 <p/>Similarly: <p/>
 <span class="name">
- entity(c, [prov:type='prov:Collection'])
+ entity(c, [prov:type='prov:EmptyCollection'])
  memberOf(c, E, true)
  derivedByInsertionFrom(c1, c, E1)
  derivedByInsertionFrom(c2, c1, E2) 
 </span>
         &rArr;   Contents(c2) = E &cup; E1 &cup; E2
 
+<p/>But in other cases, the presence of additional unknown content cannot be excluded, for instance: <p/>
+<span class="name">
+ entity(c, [prov:type='prov:Collection'])
+ memberOf(c, E)
+ derivedByInsertionFrom(c1, c, E1)
+</span>
+        &rArr;   Contents(c1) &sup; E &cup; E1
+
 
 
 </section>