diff -N TransientFlagDriver.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ TransientFlagDriver.java	15 Aug 2008 22:12:42 -0000	1.1
@@ -0,0 +1,33 @@

+package org.lcsim.util;
+
+import java.util.List;
+import org.lcsim.event.EventHeader;
+import org.lcsim.util.Driver;
+
+/**
+ * A simple Driver which flags a named list as being transient.
+ *
+ * @version $Id: TransientFlagDriver.java,v 1.1 2008/08/15 22:12:42 mcharles Exp $
+ */
+
+public class TransientFlagDriver extends Driver
+{
+    /** Constructor, supplying name of list to be flagged as a subset. */
+    public TransientFlagDriver(String name) {
+        super();
+	m_listName = name;
+    }
+
+    /** Process one event. */
+    public void process(EventHeader event)
+    {
+	if (event.hasItem(m_listName)) {
+	    List listToFlag = (List) (event.get(m_listName));
+	    event.getMetaData(listToFlag).setTransient(true);
+	} else {
+	    System.out.println("WARNING: Tried to set Transient flag, but event did not contain list '"+m_listName+"'");
+	}
+    }
+
+    protected String m_listName;
+}