--- a/ontology/ProvenanceOntology.owl	Fri Feb 24 00:50:24 2012 -0500
+++ b/ontology/ProvenanceOntology.owl	Fri Feb 24 00:52:21 2012 -0500
@@ -283,6 +283,7 @@
     <!-- http://www.w3.org/ns/prov#occurredDuring -->
 
     <owl:ObjectProperty rdf:about="&prov;occurredDuring">
+        <rdfs:domain rdf:resource="&prov;Durable"/>
         <rdfs:range rdf:resource="&prov;TimeInterval"/>
     </owl:ObjectProperty>
     
@@ -547,8 +548,8 @@
 
     <owl:Class rdf:about="&prov;Activity">
         <rdfs:label xml:lang="en">Activity</rdfs:label>
+        <rdfs:subClassOf rdf:resource="&prov;Durable"/>
         <rdfs:subClassOf rdf:resource="&prov;Element"/>
-        <rdfs:subClassOf rdf:resource="&prov;InstantaneousEvent"/>
         <rdfs:comment xml:lang="en">Activity is defined to be &#39;an identifiable activity, which performs a piece of work.&#39;</rdfs:comment>
         <rdfs:seeAlso rdf:resource="http://www.w3.org/2011/prov/wiki/ProvRDF#Activity"/>
     </owl:Class>
@@ -625,6 +626,12 @@
     
 
 
+    <!-- http://www.w3.org/ns/prov#Durable -->
+
+    <owl:Class rdf:about="&prov;Durable"/>
+    
+
+
     <!-- http://www.w3.org/ns/prov#Element -->
 
     <owl:Class rdf:about="&prov;Element">