diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AFlatValuePointable.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AFlatValuePointable.java
index 2416cc4..41d55b6 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AFlatValuePointable.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AFlatValuePointable.java
@@ -22,11 +22,16 @@
 import edu.uci.ics.asterix.runtime.util.container.IElementFactory;
 import edu.uci.ics.hyracks.data.std.api.IValueReference;
 
+/**
+ * This class is to represent a flat field, e.g., int field, string field, and
+ * so on, based on an binary representation
+ */
 public class AFlatValuePointable extends AbstractVisitablePointable {
 
     /**
      * DO NOT allow to create AFlatValuePointable object arbitrarily, force to
-     * use object pool based allocator
+     * use object pool based allocator. The factory is not public so that it
+     * cannot called in other places than PointableAllocator.
      */
     static IElementFactory<IVisitablePointable, IAType> FACTORY = new IElementFactory<IVisitablePointable, IAType>() {
         public AFlatValuePointable createElement(IAType type) {
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AListPointable.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AListPointable.java
index 558ec58..85b5297 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AListPointable.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AListPointable.java
@@ -31,6 +31,12 @@
 import edu.uci.ics.asterix.runtime.util.ResettableByteArrayOutputStream;
 import edu.uci.ics.asterix.runtime.util.container.IElementFactory;
 
+/**
+ * This class is to interpret the binary data representation of a list, one can
+ * call getItems and getItemTags to get pointable objects for items and item
+ * type tags
+ * 
+ */
 public class AListPointable extends AbstractVisitablePointable {
 
     /**
@@ -43,10 +49,6 @@
         }
     };
 
-    private IAType itemType;
-    private ATypeTag itemTag;
-    private boolean typedItemList = false;
-
     private final List<IVisitablePointable> items = new ArrayList<IVisitablePointable>();
     private final List<IVisitablePointable> itemTags = new ArrayList<IVisitablePointable>();
     private final PointableAllocator allocator = new PointableAllocator();
@@ -55,8 +57,12 @@
     private final ResettableByteArrayOutputStream dataBos = new ResettableByteArrayOutputStream();
     private final DataOutputStream dataDos = new DataOutputStream(dataBos);
 
+    private IAType itemType;
+    private ATypeTag itemTag;
+    private boolean typedItemList = false;
+
     /**
-     * private constructor, to prevent constructing it
+     * private constructor, to prevent constructing it arbitrarily
      * 
      * @param inputType
      *            , the input type
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/ARecordPointable.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/ARecordPointable.java
index 75a3737..8535db3 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/ARecordPointable.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/ARecordPointable.java
@@ -35,6 +35,12 @@
 import edu.uci.ics.asterix.runtime.util.container.IElementFactory;
 import edu.uci.ics.hyracks.api.dataflow.value.INullWriter;
 
+/**
+ * This class is to interpret the binary data representation of a record, one
+ * can call getFieldNames, getFieldTypeTags and getFieldValues to get pointable
+ * objects for field names, field type tags, and field values
+ * 
+ */
 public class ARecordPointable extends AbstractVisitablePointable {
 
     /**
@@ -48,32 +54,33 @@
     };
 
     // access results: field names, field types, and field values
-    private List<IVisitablePointable> fieldNames = new ArrayList<IVisitablePointable>();
-    private List<IVisitablePointable> fieldTypeTags = new ArrayList<IVisitablePointable>();
-    private List<IVisitablePointable> fieldValues = new ArrayList<IVisitablePointable>();
+    private final List<IVisitablePointable> fieldNames = new ArrayList<IVisitablePointable>();
+    private final List<IVisitablePointable> fieldTypeTags = new ArrayList<IVisitablePointable>();
+    private final List<IVisitablePointable> fieldValues = new ArrayList<IVisitablePointable>();
 
     // pointable allocator
-    private PointableAllocator allocator = new PointableAllocator();
+    private final PointableAllocator allocator = new PointableAllocator();
 
-    private byte[] typeBuffer = new byte[32768];
-    private ResettableByteArrayOutputStream typeBos = new ResettableByteArrayOutputStream();
-    private DataOutputStream typeDos = new DataOutputStream(typeBos);
+    private final byte[] typeBuffer = new byte[32768];
+    private final ResettableByteArrayOutputStream typeBos = new ResettableByteArrayOutputStream();
+    private final DataOutputStream typeDos = new DataOutputStream(typeBos);
 
-    private byte[] dataBuffer = new byte[32768];
-    private ResettableByteArrayOutputStream dataBos = new ResettableByteArrayOutputStream();
-    private DataOutputStream dataDos = new DataOutputStream(dataBos);
+    private final byte[] dataBuffer = new byte[32768];
+    private final ResettableByteArrayOutputStream dataBos = new ResettableByteArrayOutputStream();
+    private final DataOutputStream dataDos = new DataOutputStream(dataBos);
+
+    private final ARecordType inputRecType;
+
+    private final int numberOfSchemaFields;
+    private final int[] fieldOffsets;
+    private final IVisitablePointable nullReference = AFlatValuePointable.FACTORY.createElement(null);
 
     private int closedPartTypeInfoSize = 0;
-    private ARecordType inputRecType;
-
-    private int numberOfSchemaFields;
     private int offsetArrayOffset;
-    private int[] fieldOffsets;
     private ATypeTag typeTag;
-    private IVisitablePointable nullReference = AFlatValuePointable.FACTORY.createElement(null);
 
     /**
-     * private constructor, to prevent constructing it
+     * private constructor, to prevent constructing it arbitrarily
      * 
      * @param inputType
      *            , the input type
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AbstractVisitablePointable.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AbstractVisitablePointable.java
index 47fd7e5..6b844a0 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AbstractVisitablePointable.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/AbstractVisitablePointable.java
@@ -18,12 +18,17 @@
 import edu.uci.ics.asterix.runtime.pointables.base.IVisitablePointable;
 import edu.uci.ics.hyracks.data.std.api.IValueReference;
 
+/**
+ * This class implements several "routine" methods in IVisitablePointable
+ * interface, so that subclasses do not need to repeat the same code
+ * 
+ */
 public abstract class AbstractVisitablePointable implements IVisitablePointable {
 
     private byte[] data;
     private int start;
     private int len;
-    
+
     @Override
     public byte[] getByteArray() {
         return data;
@@ -45,7 +50,7 @@
         this.start = start;
         this.len = len;
     }
-    
+
     @Override
     public void set(IValueReference ivf) {
         set(ivf.getByteArray(), ivf.getStartOffset(), ivf.getLength());
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/PointableAllocator.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/PointableAllocator.java
index 2b654db..7675a2b 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/PointableAllocator.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/PointableAllocator.java
@@ -22,6 +22,11 @@
 import edu.uci.ics.asterix.runtime.util.container.IElementAllocator;
 import edu.uci.ics.asterix.runtime.util.container.ListElementAllocator;
 
+/**
+ * This class is the ONLY place to create IVisitablePointable object instances,
+ * so that all the client code are forced to have object reuse for those
+ * IVisitablePointable objects
+ */
 public class PointableAllocator {
 
     private IElementAllocator<IVisitablePointable, IAType> flatValueAllocator = new ListElementAllocator<IVisitablePointable, IAType>(
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/DefaultOpenFieldType.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/DefaultOpenFieldType.java
index f1f54bc..0c39aa0 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/DefaultOpenFieldType.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/DefaultOpenFieldType.java
@@ -22,6 +22,13 @@
 import edu.uci.ics.asterix.om.types.BuiltinType;
 import edu.uci.ics.asterix.om.types.IAType;
 
+/**
+ * This class serves as the repository for default record type and list type
+ * fields in the open part, e.g., a "record" (nested) field in the open part is
+ * always a fully open one, and a "list" field in the open part is always a list
+ * of "ANY"
+ * 
+ */
 public class DefaultOpenFieldType {
 
     // nested open field rec type
@@ -35,13 +42,13 @@
     // nested open list type
     public static AUnorderedListType NESTED_OPEN_AUNORDERED_LIST_TYPE = new AUnorderedListType(BuiltinType.ANY,
             "nested-unordered-list");
-    
-    public static IAType getDefaultOpenFieldType(ATypeTag tag){
-        if(tag.equals(ATypeTag.RECORD))
+
+    public static IAType getDefaultOpenFieldType(ATypeTag tag) {
+        if (tag.equals(ATypeTag.RECORD))
             return NESTED_OPEN_RECORD_TYPE;
-        if(tag.equals(ATypeTag.ORDEREDLIST))
+        if (tag.equals(ATypeTag.ORDEREDLIST))
             return NESTED_OPEN_AORDERED_LIST_TYPE;
-        if(tag.equals(ATypeTag.UNORDEREDLIST))
+        if (tag.equals(ATypeTag.UNORDEREDLIST))
             return NESTED_OPEN_AUNORDERED_LIST_TYPE;
         else
             return null;
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/IVisitablePointable.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/IVisitablePointable.java
index b3c088b..f630e24 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/IVisitablePointable.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/base/IVisitablePointable.java
@@ -19,6 +19,10 @@
 import edu.uci.ics.asterix.runtime.pointables.visitor.IVisitablePointableVisitor;
 import edu.uci.ics.hyracks.data.std.api.IPointable;
 
+/**
+ * This interface extends IPointable with a visitor interface in order to ease
+ * programming for recursive record structures
+ */
 public interface IVisitablePointable extends IPointable {
 
     public <R, T> R accept(IVisitablePointableVisitor<R, T> vistor, T tag) throws AsterixException;
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ACastVisitor.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ACastVisitor.java
index 67ff67e..9d3fe73 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ACastVisitor.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ACastVisitor.java
@@ -29,13 +29,27 @@
 import edu.uci.ics.asterix.runtime.pointables.visitor.IVisitablePointableVisitor;
 import edu.uci.ics.hyracks.algebricks.common.utils.Triple;
 
+/**
+ * This class is a IVisitablePointableVisitor implementation which recursively
+ * visit a given record, list or flat value of a given type, and recursively
+ * cast it to a specified type For example,
+ * 
+ * A record { "hobby": {{"music", "coding"}}, "id": "001", "name":
+ * "Person Three"} which confirms to closed type ( id: string, name: string,
+ * hobby: {{string}}? ) can be casted to a open type (id: string )
+ * 
+ * Since the open/close part of a record has completely different underlying
+ * memory/storage layout, the visitor will change the layout as specified at
+ * runtime.
+ */
 public class ACastVisitor implements IVisitablePointableVisitor<Void, Triple<IVisitablePointable, IAType, Boolean>> {
 
-    private Map<IVisitablePointable, ARecordCaster> raccessorToCaster = new HashMap<IVisitablePointable, ARecordCaster>();
-    private Map<IVisitablePointable, AListCaster> laccessorToCaster = new HashMap<IVisitablePointable, AListCaster>();
+    private final Map<IVisitablePointable, ARecordCaster> raccessorToCaster = new HashMap<IVisitablePointable, ARecordCaster>();
+    private final Map<IVisitablePointable, AListCaster> laccessorToCaster = new HashMap<IVisitablePointable, AListCaster>();
 
     @Override
-    public Void visit(AListPointable accessor, Triple<IVisitablePointable, IAType, Boolean> arg) throws AsterixException {
+    public Void visit(AListPointable accessor, Triple<IVisitablePointable, IAType, Boolean> arg)
+            throws AsterixException {
         AListCaster caster = laccessorToCaster.get(accessor);
         if (caster == null) {
             caster = new AListCaster();
@@ -50,7 +64,8 @@
     }
 
     @Override
-    public Void visit(ARecordPointable accessor, Triple<IVisitablePointable, IAType, Boolean> arg) throws AsterixException {
+    public Void visit(ARecordPointable accessor, Triple<IVisitablePointable, IAType, Boolean> arg)
+            throws AsterixException {
         ARecordCaster caster = raccessorToCaster.get(accessor);
         if (caster == null) {
             caster = new ARecordCaster();
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/AListCaster.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/AListCaster.java
index 930bb8b..9423a0c 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/AListCaster.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/AListCaster.java
@@ -36,23 +36,27 @@
 import edu.uci.ics.asterix.runtime.util.ResettableByteArrayOutputStream;
 import edu.uci.ics.hyracks.algebricks.common.utils.Triple;
 
+/**
+ * This class is to do the runtime type cast for a list. It is ONLY visible to
+ * ACastVisitor, so that no other client places can call into that caster and
+ * unnecessary bugs could be prevented.
+ */
 class AListCaster {
-
-    private IAType reqItemType;
     // pointable allocator
-    private PointableAllocator allocator = new PointableAllocator();
+    private final PointableAllocator allocator = new PointableAllocator();
 
     // for storing the cast result
-    private IVisitablePointable itemTempReference = allocator.allocateEmpty();
-    private Triple<IVisitablePointable, IAType, Boolean> itemVisitorArg = new Triple<IVisitablePointable, IAType, Boolean>(
+    private final IVisitablePointable itemTempReference = allocator.allocateEmpty();
+    private final Triple<IVisitablePointable, IAType, Boolean> itemVisitorArg = new Triple<IVisitablePointable, IAType, Boolean>(
             itemTempReference, null, null);
 
-    private UnorderedListBuilder unOrderedListBuilder = new UnorderedListBuilder();
-    private OrderedListBuilder orderedListBuilder = new OrderedListBuilder();
+    private final UnorderedListBuilder unOrderedListBuilder = new UnorderedListBuilder();
+    private final OrderedListBuilder orderedListBuilder = new OrderedListBuilder();
 
-    private byte[] dataBuffer = new byte[32768];
-    private ResettableByteArrayOutputStream dataBos = new ResettableByteArrayOutputStream();
-    private DataOutput dataDos = new DataOutputStream(dataBos);
+    private final ResettableByteArrayOutputStream dataBos = new ResettableByteArrayOutputStream();
+    private final DataOutput dataDos = new DataOutputStream(dataBos);
+    private final byte[] dataBuffer = new byte[32768];
+    private IAType reqItemType;
 
     public AListCaster() {
 
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ARecordCaster.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ARecordCaster.java
index 52aab9d..70fbc4a 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ARecordCaster.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/pointables/cast/ARecordCaster.java
@@ -41,11 +41,41 @@
 import edu.uci.ics.hyracks.data.std.accessors.PointableBinaryComparatorFactory;
 import edu.uci.ics.hyracks.data.std.api.IValueReference;
 import edu.uci.ics.hyracks.data.std.primitive.UTF8StringPointable;
+import edu.uci.ics.hyracks.dataflow.common.comm.io.ByteArrayAccessibleOutputStream;
 
+/**
+ * This class is to do the runtime type cast for a record. It is ONLY visible to
+ * ACastVisitor, so that no other client places can call into that caster and
+ * unnecessary bugs could be prevented.
+ */
 class ARecordCaster {
 
     // pointable allocator
-    private PointableAllocator allocator = new PointableAllocator();
+    private final PointableAllocator allocator = new PointableAllocator();
+
+    private final List<IVisitablePointable> reqFieldNames = new ArrayList<IVisitablePointable>();
+    private final List<IVisitablePointable> reqFieldTypeTags = new ArrayList<IVisitablePointable>();
+    private ARecordType cachedReqType = null;
+
+    private final byte[] buffer = new byte[32768];
+    private final ResettableByteArrayOutputStream bos = new ResettableByteArrayOutputStream();
+    private final DataOutputStream dos = new DataOutputStream(bos);
+
+    private final RecordBuilder recBuilder = new RecordBuilder();
+    private final IVisitablePointable nullReference = allocator.allocateEmpty();
+    private final IVisitablePointable nullTypeTag = allocator.allocateEmpty();
+
+    private final IBinaryComparator fieldNameComparator = PointableBinaryComparatorFactory.of(
+            UTF8StringPointable.FACTORY).createBinaryComparator();
+
+    private final ByteArrayAccessibleOutputStream outputBos = new ByteArrayAccessibleOutputStream();
+    private final DataOutputStream outputDos = new DataOutputStream(outputBos);
+
+    private final IVisitablePointable fieldTempReference = allocator.allocateEmpty();
+    private final Triple<IVisitablePointable, IAType, Boolean> nestedVisitorArg = new Triple<IVisitablePointable, IAType, Boolean>(
+            fieldTempReference, null, null);
+
+    private int numInputFields = 0;
 
     // describe closed fields in the required type
     private int[] fieldPermutation;
@@ -54,31 +84,7 @@
     // describe fields (open or not) in the input records
     private boolean[] openFields;
     private int[] fieldNamesSortedIndex;
-
-    private List<IVisitablePointable> reqFieldNames = new ArrayList<IVisitablePointable>();
     private int[] reqFieldNamesSortedIndex;
-    private List<IVisitablePointable> reqFieldTypeTags = new ArrayList<IVisitablePointable>();
-    private ARecordType cachedReqType = null;
-
-    private byte[] buffer = new byte[32768];
-    private ResettableByteArrayOutputStream bos = new ResettableByteArrayOutputStream();
-    private DataOutputStream dos = new DataOutputStream(bos);
-
-    private RecordBuilder recBuilder = new RecordBuilder();
-    private IVisitablePointable nullReference = allocator.allocateEmpty();
-    private IVisitablePointable nullTypeTag = allocator.allocateEmpty();
-
-    private int numInputFields = 0;
-    private IBinaryComparator fieldNameComparator = PointableBinaryComparatorFactory.of(UTF8StringPointable.FACTORY)
-            .createBinaryComparator();
-
-    private byte[] outputBuffer = new byte[32768];
-    private ResettableByteArrayOutputStream outputBos = new ResettableByteArrayOutputStream();
-    private DataOutputStream outputDos = new DataOutputStream(outputBos);
-
-    private IVisitablePointable fieldTempReference = allocator.allocateEmpty();
-    private Triple<IVisitablePointable, IAType, Boolean> nestedVisitorArg = new Triple<IVisitablePointable, IAType, Boolean>(
-            fieldTempReference, null, null);
 
     public ARecordCaster() {
         try {
@@ -116,7 +122,7 @@
         reset();
         matchClosedPart(fieldNames, fieldTypeTags, fieldValues);
         writeOutput(fieldNames, fieldTypeTags, fieldValues, outputDos, visitor);
-        resultAccessor.set(outputBuffer, 0, outputBos.size());
+        resultAccessor.set(outputBos.getByteArray(), 0, outputBos.size());
     }
 
     private void reset() {
@@ -126,7 +132,7 @@
             fieldPermutation[i] = -1;
         for (int i = 0; i < numInputFields; i++)
             fieldNamesSortedIndex[i] = i;
-        outputBos.setByteArray(outputBuffer, 0);
+        outputBos.reset();
     }
 
     private void loadRequiredType(ARecordType reqType) throws IOException {
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/ResettableByteArrayInputStream.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/ResettableByteArrayInputStream.java
deleted file mode 100644
index af18133..0000000
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/ResettableByteArrayInputStream.java
+++ /dev/null
@@ -1,61 +0,0 @@
-/*
- * Copyright 2009-2010 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.asterix.runtime.util;
-
-import java.io.ByteArrayInputStream;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-public class ResettableByteArrayInputStream extends ByteArrayInputStream {
-    private static final Logger LOGGER = Logger.getLogger(ResettableByteArrayInputStream.class.getName());
-
-    private byte[] data;
-    private int position;
-
-    public ResettableByteArrayInputStream(byte[] data) {
-        super(data);
-    }
-
-    public void setByteArray(byte[] data, int position) {
-        this.data = data;
-        this.position = position;
-    }
-
-    @Override
-    public int read() {
-        int remaining = data.length - position;
-        int value = remaining > 0 ? (data[position++] & 0xff) : -1;
-        if (LOGGER.isLoggable(Level.FINEST)) {
-            LOGGER.finest("read(): value: " + value + " remaining: " + remaining + " position: " + position);
-        }
-        return value;
-    }
-
-    @Override
-    public int read(byte[] bytes, int offset, int length) {
-        int remaining = data.length - position;
-        if (LOGGER.isLoggable(Level.FINEST)) {
-            LOGGER.finest("read(bytes[], int, int): remaining: " + remaining + " offset: " + offset + " length: "
-                    + length + " position: " + position);
-        }
-        if (remaining == 0) {
-            return -1;
-        }
-        int l = Math.min(length, remaining);
-        System.arraycopy(data, position, bytes, offset, l);
-        position += l;
-        return l;
-    }
-}
\ No newline at end of file
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementAllocator.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementAllocator.java
index b99f379..8172e56 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementAllocator.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementAllocator.java
@@ -20,7 +20,19 @@
  */
 public interface IElementAllocator<E, T> {
 
+    /**
+     * Give client an E instance
+     * 
+     * @param arg
+     *            , the argument to create E
+     * @return a E instance
+     */
     public E allocate(T arg);
 
+    /**
+     * Clean all the used(assigned) instances in the pool. Then all instances in
+     * the pool are marked as "unused" and can be returned to next bunch of
+     * allocate call from a client
+     */
     public void reset();
 }
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementFactory.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementFactory.java
index 293720e..f914d13 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementFactory.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/IElementFactory.java
@@ -16,13 +16,16 @@
 package edu.uci.ics.asterix.runtime.util.container;
 
 /**
- * A factory interface to create elements
+ * A factory interface to create elements. Elements in a reusable pool/container
+ * can ONLY be instantiated from the corresponding factory
  */
 public interface IElementFactory<E, T> {
 
     /**
      * create an element of type E
-     * @param arg of type T
+     * 
+     * @param arg
+     *            of type T
      * @return an E element
      */
     public E createElement(T arg);
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/ListElementAllocator.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/ListElementAllocator.java
index a2b2273..dc96153 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/ListElementAllocator.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/util/container/ListElementAllocator.java
@@ -25,7 +25,11 @@
  * other words, however elements in the list should be exactly the same class,
  * this is forced by IElementFactory<E, T> factory as a parameter to the
  * constructor once a ListElementAllocator is constructed, it can only store
- * objects of the same class
+ * objects of the same class.
+ * 
+ * The argument for creating E instances could be different. This class also
+ * considers arguments in object reusing, e.g., reuse an E instances ONLY when
+ * the construction argument is "equal".
  */
 public class ListElementAllocator<E, T> implements IElementAllocator<E, T> {