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diff --git a/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/SingleSetAsyncListener.java b/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/SingleSetAsyncListener.java
new file mode 100644
index 000000000..7a30cc591
--- /dev/null
+++ b/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/SingleSetAsyncListener.java
@@ -0,0 +1,68 @@
+/*******************************************************************************
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management
+ * in Industry THTH ry.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     VTT Technical Research Centre of Finland - initial API and implementation
+ *******************************************************************************/
+package org.simantics.db.common.procedure.single;
+
+import java.util.Collection;
+import java.util.HashSet;
+
+import org.simantics.db.AsyncReadGraph;
+import org.simantics.db.procedure.AsyncListener;
+
+abstract public class SingleSetAsyncListener<T> implements AsyncListener<Collection<T>>{
+    
+	final private boolean changesOnly;
+	private Collection<T> previous = null;
+    
+    public void add(AsyncReadGraph graph, T item) {}
+    public void remove(AsyncReadGraph graph, T item) {}
+    
+    public SingleSetAsyncListener() {
+    	this(false);
+    }
+    
+    public SingleSetAsyncListener(boolean changesOnly) {
+    	this.changesOnly = changesOnly;
+    }
+
+    @Override
+    public void execute(AsyncReadGraph graph, final Collection<T> result) {
+    	
+        if(previous == null) {
+
+        	if(!changesOnly) {
+//        		for(T t : result)
+//        			add(graph, t);
+//        	} else {
+        		first(graph, result);
+        	}
+
+        } else {
+
+            HashSet<T> added = new HashSet<T>(result);
+            added.removeAll(previous);
+            HashSet<T> removed = new HashSet<T>(previous);
+            removed.removeAll(result);
+
+            for(T t : added) add(graph, t);
+            for(T t : removed) remove(graph, t);
+
+        }
+
+        previous = result;
+        
+    }
+    
+    public void first(AsyncReadGraph graph, final Collection<T> result) {
+    	for(T t : result) add(graph, t);
+    }
+	
+}