diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalExpression.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalExpression.java
index 84d7fab..c4ae9bc 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalExpression.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalExpression.java
@@ -67,4 +67,6 @@
     public boolean splitIntoConjuncts(List<Mutable<ILogicalExpression>> conjs);
 
     public abstract ILogicalExpression cloneExpression();
+
+    public boolean isFunctional();
 }
\ No newline at end of file
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractFunctionCallExpression.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractFunctionCallExpression.java
index 0c19c79..e360682 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractFunctionCallExpression.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractFunctionCallExpression.java
@@ -323,4 +323,16 @@
         }
     }
 
+    @Override
+    public boolean isFunctional() {
+        if (finfo.isFunctional()) {
+            for (Mutable<ILogicalExpression> e : arguments) {
+                if (!e.getValue().isFunctional()) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
 }
\ No newline at end of file
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractLogicalExpression.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractLogicalExpression.java
index abc46c0..2718076 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractLogicalExpression.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/AbstractLogicalExpression.java
@@ -36,4 +36,9 @@
         // do nothing
     }
 
+    @Override
+    public boolean isFunctional() {
+        return true;
+    }
+
 }
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/ConstantExpression.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/ConstantExpression.java
index 0482133..1a3fe47 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/ConstantExpression.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/ConstantExpression.java
@@ -170,4 +170,5 @@
     public boolean splitIntoConjuncts(List<Mutable<ILogicalExpression>> conjs) {
         return false;
     }
+
 }
\ No newline at end of file
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/functions/AbstractFunctionInfo.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/functions/AbstractFunctionInfo.java
new file mode 100644
index 0000000..fe47def
--- /dev/null
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/functions/AbstractFunctionInfo.java
@@ -0,0 +1,20 @@
+package edu.uci.ics.hyracks.algebricks.core.algebra.functions;
+
+import java.io.Serializable;
+
+public abstract class AbstractFunctionInfo implements IFunctionInfo, Serializable {
+
+    private static final long serialVersionUID = 1L;
+
+    private final boolean isFunctional;
+
+    protected AbstractFunctionInfo(boolean isFunctional) {
+        this.isFunctional = isFunctional;
+    }
+
+    @Override
+    public boolean isFunctional() {
+        return isFunctional;
+    }
+
+}
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java
index 4c294a7..02cd6de 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java
@@ -14,7 +14,8 @@
  */
 package edu.uci.ics.hyracks.algebricks.core.algebra.functions;
 
-
 public interface IFunctionInfo {
     FunctionIdentifier getFunctionIdentifier();
+
+    public boolean isFunctional();
 }
diff --git a/algebricks/algebricks-examples/piglet-example/src/main/java/edu/uci/ics/hyracks/algebricks/examples/piglet/metadata/PigletFunction.java b/algebricks/algebricks-examples/piglet-example/src/main/java/edu/uci/ics/hyracks/algebricks/examples/piglet/metadata/PigletFunction.java
index 47148ac..ba5c5aa 100644
--- a/algebricks/algebricks-examples/piglet-example/src/main/java/edu/uci/ics/hyracks/algebricks/examples/piglet/metadata/PigletFunction.java
+++ b/algebricks/algebricks-examples/piglet-example/src/main/java/edu/uci/ics/hyracks/algebricks/examples/piglet/metadata/PigletFunction.java
@@ -14,13 +14,16 @@
  */
 package edu.uci.ics.hyracks.algebricks.examples.piglet.metadata;
 
+import edu.uci.ics.hyracks.algebricks.core.algebra.functions.AbstractFunctionInfo;
 import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
-import edu.uci.ics.hyracks.algebricks.core.algebra.functions.IFunctionInfo;
 
-public class PigletFunction implements IFunctionInfo {
+public class PigletFunction extends AbstractFunctionInfo {
+    private static final long serialVersionUID = 1L;
+
     private final FunctionIdentifier fid;
 
     public PigletFunction(FunctionIdentifier fid) {
+        super(true);
         this.fid = fid;
     }
 
diff --git a/hivesterix/hivesterix-common/src/main/java/edu/uci/ics/hivesterix/logical/expression/HiveFunctionInfo.java b/hivesterix/hivesterix-common/src/main/java/edu/uci/ics/hivesterix/logical/expression/HiveFunctionInfo.java
index 4f4ca90..95b63b7 100644
--- a/hivesterix/hivesterix-common/src/main/java/edu/uci/ics/hivesterix/logical/expression/HiveFunctionInfo.java
+++ b/hivesterix/hivesterix-common/src/main/java/edu/uci/ics/hivesterix/logical/expression/HiveFunctionInfo.java
@@ -12,39 +12,38 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package edu.uci.ics.hivesterix.logical.expression;
-
-import java.io.Serializable;
-
-import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
-import edu.uci.ics.hyracks.algebricks.core.algebra.functions.IFunctionInfo;
-
-public class HiveFunctionInfo implements IFunctionInfo, Serializable {
-
-    private static final long serialVersionUID = 1L;
-
-    /**
-     * primary function identifier
-     */
-    private transient FunctionIdentifier fid;
-
-    /**
-     * secondary function identifier: function name
-     */
-    private transient Object secondaryFid;
-
-    public HiveFunctionInfo(FunctionIdentifier fid, Object secondFid) {
-        this.fid = fid;
-        this.secondaryFid = secondFid;
-    }
-
-    @Override
-    public FunctionIdentifier getFunctionIdentifier() {
-        return fid;
-    }
-
-    public Object getInfo() {
-        return secondaryFid;
-    }
-
-}
+package edu.uci.ics.hivesterix.logical.expression;
+
+import edu.uci.ics.hyracks.algebricks.core.algebra.functions.AbstractFunctionInfo;
+import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
+
+public class HiveFunctionInfo extends AbstractFunctionInfo {
+
+    private static final long serialVersionUID = 1L;
+
+    /**
+     * primary function identifier
+     */
+    private transient FunctionIdentifier fid;
+
+    /**
+     * secondary function identifier: function name
+     */
+    private transient Object secondaryFid;
+
+    public HiveFunctionInfo(FunctionIdentifier fid, Object secondFid) {
+        super(true);
+        this.fid = fid;
+        this.secondaryFid = secondFid;
+    }
+
+    @Override
+    public FunctionIdentifier getFunctionIdentifier() {
+        return fid;
+    }
+
+    public Object getInfo() {
+        return secondaryFid;
+    }
+
+}