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diff --git a/qpid/tools/src/java/qpid-qmf2/src/main/java/org/apache/qpid/qmf2/common/Expression.java b/qpid/tools/src/java/qpid-qmf2/src/main/java/org/apache/qpid/qmf2/common/Expression.java
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+++ b/qpid/tools/src/java/qpid-qmf2/src/main/java/org/apache/qpid/qmf2/common/Expression.java
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+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.qpid.qmf2.common;
+
+// Misc Imports
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * This class represents the base class for all Expressions created by expanding the Query predicate.
+ * <p>
+ * Depending on the structure of the expression list there might be a nested structure of Expressions comprising
+ * a mixture of LogicalExpressions and BooleanExpressions.
+ * <p>
+ * The Expression structure is illustrated below in the context of its relationship with QmfQuery.
+ * <img alt="" src="doc-files/QmfQuery.png">
+ *
+ * @author Fraser Adams
+ */
+public abstract class Expression
+{
+    /**
+     * Factory method to create concrete Expression instances base on the operator name extracted from the expression List.
+     * This method will create a LogicalExpression from an "and", "or" or "not" operator otherwise it will create
+     * a BooleanExpression.
+     *
+     * @param expr the List of Expressions extracted by parsing the Query predicate
+     */
+    public static Expression createExpression(final List expr) throws QmfException
+    {
+        Iterator iter = expr.listIterator();
+        if (!iter.hasNext())
+        {
+            throw new QmfException("Missing operator in predicate expression");
+        }
+
+        String op = (String)iter.next();
+        if (op.equals("not"))
+        {
+            return new LogicalNot(expr);
+        }
+        if (op.equals("and"))
+        {
+            return new LogicalAnd(expr);
+        }
+        if (op.equals("or"))
+        {
+            return new LogicalOr(expr);
+        }
+        return BooleanExpression.createExpression(expr);
+    }    
+
+    /**
+     * Evaluate expression against a QmfData instance.
+     * @return true if query matches the QmfData instance, else false.
+     */
+    public abstract boolean evaluate(final QmfData data);
+}
+