diff --git a/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluator.java b/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluator.java
index 5f022ca..575472c 100644
--- a/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluator.java
+++ b/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluator.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2009-2010 by The Regents of the University of California
+ * Copyright 2009-2013 by The Regents of the University of California
  * 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 from
@@ -17,6 +17,9 @@
 
 import edu.uci.ics.hyracks.api.comm.IFrameTupleAccessor;
 
+/*
+ * Compares two tuples to make sure that records, whose comparison keys are NULL do not pass comparator filter  
+ */
 public interface IPredicateEvaluator {
 	public boolean evaluate(IFrameTupleAccessor fta0, int tupId0, IFrameTupleAccessor fta1, int tupId1);
 }
diff --git a/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactory.java b/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactory.java
index 6bf82da..bc2f339 100644
--- a/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactory.java
+++ b/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactory.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2009-2010 by The Regents of the University of California
+ * Copyright 2009-2013 by The Regents of the University of California
  * 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 from
@@ -17,6 +17,10 @@
 
 import java.io.Serializable;
 
+/*
+ * Provides PredicateEvaluator for equi-join related operators 
+ */
+
 public interface IPredicateEvaluatorFactory extends Serializable {
 	public IPredicateEvaluator createPredicateEvaluator();
 }
diff --git a/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactoryProvider.java b/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactoryProvider.java
index 5646a34..029ab21 100644
--- a/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactoryProvider.java
+++ b/hyracks/hyracks-api/src/main/java/edu/uci/ics/hyracks/api/dataflow/value/IPredicateEvaluatorFactoryProvider.java
@@ -1,7 +1,26 @@
+/*
+ * Copyright 2009-2013 by The Regents of the University of California
+ * 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 from
+ * 
+ *     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 edu.uci.ics.hyracks.api.dataflow.value;
 
 import java.io.Serializable;
 
+/*
+ * Provides PredicateEvaluatorFactory based on (equi-join) keys 		
+ */
+
 public interface IPredicateEvaluatorFactoryProvider extends Serializable{
 	public IPredicateEvaluatorFactory getPredicateEvaluatorFactory(int[] keys0, int[] keys1);
 }