diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalOperator.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalOperator.java
index c11dd80..d786cff 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalOperator.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/ILogicalOperator.java
@@ -32,6 +32,8 @@
 
 public interface ILogicalOperator {
 
+    public LogicalOperatorTag getOperatorTag();
+
     public List<Mutable<ILogicalOperator>> getInputs();
 
     boolean hasInputs();
@@ -89,7 +91,7 @@
     public IPhysicalPropertiesVector getDeliveredPhysicalProperties();
 
     public void computeDeliveredPhysicalProperties(IOptimizationContext context) throws AlgebricksException;
-    
+
     /**
      * Indicates whether the expressions used by this operator must be variable reference expressions.
      */
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/AbstractLogicalOperator.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/AbstractLogicalOperator.java
index a7e8479..78efd0d 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/AbstractLogicalOperator.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/AbstractLogicalOperator.java
@@ -69,6 +69,7 @@
         // outputs = new ArrayList<LogicalOperatorReference>();
     }
 
+    @Override
     public abstract LogicalOperatorTag getOperatorTag();
 
     public ExecutionMode getExecutionMode() {
@@ -182,7 +183,7 @@
         return new PropagatingTypeEnvironment(ctx.getExpressionTypeComputer(), ctx.getNullableTypeComputer(),
                 ctx.getMetadataProvider(), TypePropagationPolicy.ALL, envPointers);
     }
-    
+
     @Override
     public boolean requiresVariableReferenceExpressions() {
         return true;