--- a/model/ProvenanceModel.html	Thu Dec 08 23:01:47 2011 +0000
+++ b/model/ProvenanceModel.html	Thu Dec 08 23:06:15 2011 +0000
@@ -997,7 +997,7 @@
 <li><em>recipeLink</em>: an OPTIONAL <a href="#record-RecipeLink">recipe link</a> <span class="name">rl</span>, which consists of a domain specific specification of the activity;</li>
 <li><em>startTime</em>: an OPTIONAL time <span class="name">st</span> indicating the start of the activity;</li>
 <li><em>endTime</em>: an OPTIONAL time <span class="name">et</span> indicating the end of the activity;</li>
-<li><em>attributes</em>:  a set of attribute-value pairs <span class="name">[ attr1=val1, ...]</span>, representing other attributes of this activity that hold for its whole duration.</li>
+<li><em>attributes</em>:  an OPTIONAL set of attribute-value pairs <span class="name">[ attr1=val1, ...]</span>, representing other attributes of this activity that hold for its whole duration.</li>
 </ul>
 
 <p>In PROV-ASN, an activity record's text matches the <span class='nonterminal'>activityRecord</span> production of the grammar defined in this specification document.</p>