Index: trunk/autoquest-core-tasktrees/src/main/java/de/ugoe/cs/autoquest/tasktrees/treeifc/DefaultTaskInstanceTraversingVisitor.java
===================================================================
--- trunk/autoquest-core-tasktrees/src/main/java/de/ugoe/cs/autoquest/tasktrees/treeifc/DefaultTaskInstanceTraversingVisitor.java	(revision 1406)
+++ trunk/autoquest-core-tasktrees/src/main/java/de/ugoe/cs/autoquest/tasktrees/treeifc/DefaultTaskInstanceTraversingVisitor.java	(revision 1406)
@@ -0,0 +1,103 @@
+//   Copyright 2012 Georg-August-Universität Göttingen, Germany
+//
+//   Licensed under the Apache License, Version 2.0 (the "License");
+//   you may not use this file except in compliance with the License.
+//   You may obtain a copy of the License at
+//
+//       http://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+package de.ugoe.cs.autoquest.tasktrees.treeifc;
+
+/**
+ * <p>
+ * Default implementation for a task instance visitor performing a traversal of the instances
+ * </p>
+ * 
+ * @author Patrick Harms
+ */
+public class DefaultTaskInstanceTraversingVisitor implements ITaskInstanceVisitor {
+
+    /* (non-Javadoc)
+     * @see de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskInstanceVisitor#visit(IEventTaskInstance)
+     */
+    @Override
+    public void visit(IEventTaskInstance eventTaskInstance) {
+        // do nothing
+    }
+
+    /* (non-Javadoc)
+     * @see de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskInstanceVisitor#visit(IIterationInstance)
+     */
+    @Override
+    public void visit(IIterationInstance iterationInstance) {
+        visit((ITaskInstanceList) iterationInstance);
+    }
+
+    /* (non-Javadoc)
+     * @see de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskInstanceVisitor#visit(IOptionalInstance)
+     */
+    @Override
+    public void visit(IOptionalInstance optionalInstance) {
+        if (optionalInstance.getChild() != null) {
+            optionalInstance.getChild().accept(this);
+        }
+    }
+
+    /* (non-Javadoc)
+     * @see de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskInstanceVisitor#visit(ISelectionInstance)
+     */
+    @Override
+    public void visit(ISelectionInstance selectionInstance) {
+        selectionInstance.getChild().accept(this);
+    }
+
+    /* (non-Javadoc)
+     * @see de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskInstanceVisitor#visit(ISequenceInstance)
+     */
+    @Override
+    public void visit(ISequenceInstance sequenceInstance) {
+        visit((ITaskInstanceList) sequenceInstance);
+    }
+
+    /* (non-Javadoc)
+     * @see de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskInstanceVisitor#visit(ITaskInstance)
+     */
+    @Override
+    public void visit(ITaskInstance taskInstance) {
+        if (taskInstance instanceof IEventTaskInstance) {
+            visit((IEventTaskInstance) taskInstance);
+        }
+        else if (taskInstance instanceof IIterationInstance) {
+            visit((IIterationInstance) taskInstance);
+        }
+        else if (taskInstance instanceof IOptionalInstance) {
+            visit((IOptionalInstance) taskInstance);
+        }
+        else if (taskInstance instanceof ISelectionInstance) {
+            visit((ISelectionInstance) taskInstance);
+        }
+        else if (taskInstance instanceof ISequenceInstance) {
+            visit((ISequenceInstance) taskInstance);
+        }
+    }
+
+
+    /**
+     * <p>
+     * common implementation for traversing task instance lists.
+     * </p>
+     * 
+     * @param taskInstanceList the task instance list to be traversed
+     */
+    public void visit(ITaskInstanceList taskInstanceList) {
+        for (ITaskInstance child : taskInstanceList) {
+            child.accept(this);
+        }
+    }
+}