--- a/model/ProvenanceModel.html	Wed Sep 14 13:39:34 2011 +0100
+++ b/model/ProvenanceModel.html	Wed Sep 14 14:55:13 2011 +0100
@@ -1650,22 +1650,31 @@
 <span class="name">(</span> 
 <span class="nonterminal">identifier</span> 
 <span class="name">,</span> 
-<span class="nonterminal">identifier</span> 
+<span class="nonterminal">asserter</span> 
 <span class="name">,</span> 
-<span class="name">[</span> 
 { <span class="nonterminal">expression</span> }
-<span class="name">]</span> 
 <span class="name">)</span> 
 </div>
 
-<p>An instance of an account expression, noted <span class="name">account(id, a, constructs)</span> in PROV-ASN:
+<p>An instance of an account expression, noted <span class="name">account(id, http://x.com/user1, exprs)</span> in PROV-ASN:
 <ul>
-<li> contains an identifier <span class="name">id</span> intended to name this account;</li>
-<li> refers to an agent denoted by identifier <span class="name">a</span>;</li>
-<li> contains a set of provenance constructs <span class="name">constructs</span>.</li>
+<li> contains an identifier <span class="name">id</span> to identify this account;</li>
+<li> contains an asserter identified by URI <span class="name">http://x.com/user1</span>;</li>
+<li> contains a <em>set</em> of provenance expressions <span class="name">exprs</span>.</li>
 </ul>
 </p>
 
+<p>Account expressions constitue a scope for identifiers. An identifier within the scope of an account is intended to denote a single expression. However, nothing prevents an asserter from asserting an account containing, for example,  multiple entity expressions with a same identifier but different attribute-values. In that case, this should be understood the entity expression with this identifier, with the union of all attributes values, as formalized in <a href="#identified-entity-in-account">identifier-in-account</a>.</p>
+
+<div class='constraint' id='identified-entity-in-account'>
+Given an identifiers <span class="name">e</span>,  two set of attribute-values <span class="name">av1</span> and <span class="name">av2</span>, 
+ two entity expressions  <span class="name">entity(e,av1)</span> and <span class="name">entity(e,av2)</span> occurring in an account  are equivalent to the entity expression <span class="name">entity(e,av)</span> where <span class="name">av</span> is the set given by the union of <span class="name">av1</span> and <span class="name">av2</span>.
+</div>
+
+<div class='note'>Luc: explain this may lead to inconsistency when attribute have different values. Also, extend to any expression with identity (agent,annotation) </div>
+
+<p>Account expressions can be nested since  an account expression can occur among the expressions being wrapped by another account. </p>
+
 <p>
 The following account expression
 <pre class="example">