diff --git a/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/OperatorTypeMap.java b/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/OperatorTypeMap.java
index 3505748..1737817 100644
--- a/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/OperatorTypeMap.java
+++ b/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/OperatorTypeMap.java
@@ -79,8 +79,7 @@ public class OperatorTypeMap {
 		case ANY:
 			break;
 		case BEGINS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextBeginsWith(placeHolder,new C_ConstantList(arguments));
+			exp=new C_TextBeginsWith(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case BETWEEN:
 			fArg=new TD_Value(dataType,firstArg);
@@ -116,23 +115,19 @@ public class OperatorTypeMap {
 		case DIVISION:
 			break;
 		case ENDS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextEndsWith(placeHolder,new C_ConstantList(arguments));
+			exp=new C_TextEndsWith(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_Equals(placeHolder,new C_ConstantList(arguments));
+			exp=new C_Equals(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case EXISTS:
 			//exp=new C_Exi(placeHolder,new C_ConstantList(arguments));
 			break;
 		case GREATER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_GreaterThan(placeHolder,new C_ConstantList(arguments));
+			exp=new C_GreaterThan(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case GREATER_OR_EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_GreaterOrEquals(placeHolder,new C_ConstantList(arguments));
+			exp=new C_GreaterOrEquals(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case IN:
 			break;
@@ -143,18 +138,15 @@ public class OperatorTypeMap {
 			exp=new C_IsNull(placeHolder);
 			break;
 		case LESSER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_LessThan(placeHolder,new C_ConstantList(arguments));
+			exp=new C_LessThan(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case LESSER_OR_EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_LessOrEquals(placeHolder,new C_ConstantList(arguments));	
+			exp=new C_LessOrEquals(placeHolder,new TD_Value(dataType,firstArg));	
 			break;
 		case LIKE:
 			break;
 		case MATCH_REGEX:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextMatchSQLRegexp(placeHolder,new C_ConstantList(arguments));
+			exp=new C_TextMatchSQLRegexp(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case MODULUS:
 			break;
@@ -163,8 +155,7 @@ public class OperatorTypeMap {
 		case NOT:
 			break;
 		case NOT_BEGINS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextBeginsWith(placeHolder,new C_ConstantList(arguments));
+			exp=new C_TextBeginsWith(placeHolder, new TD_Value(dataType,firstArg));
 			exp=new C_Not(exp);
 			break;
 		case NOT_BETWEEN:
@@ -201,29 +192,24 @@ public class OperatorTypeMap {
 			exp=new C_Not(exp);
 			break;
 		case NOT_ENDS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextEndsWith(placeHolder,new C_ConstantList(arguments));
+			exp=new C_TextEndsWith(placeHolder,new TD_Value(dataType,firstArg));
 			exp=new C_Not(exp);
 			break;
 		case NOT_EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_NotEquals(placeHolder,new C_ConstantList(arguments));
+			exp=new C_NotEquals(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case NOT_GREATER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_NotGreater(placeHolder,new C_ConstantList(arguments));
+			exp=new C_NotGreater(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case NOT_IN:
 			break;
 		case NOT_LESSER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_NotLess(placeHolder,new C_ConstantList(arguments));
+			exp=new C_NotLess(placeHolder,new TD_Value(dataType,firstArg));
 			break;
 		case NOT_LIKE:
 			break;
 		case NOT_MATCH_REGEX:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextMatchSQLRegexp(placeHolder,new C_ConstantList(arguments));
+			exp=new C_TextMatchSQLRegexp(placeHolder,new TD_Value(dataType,firstArg));
 			exp=new C_Not(exp);
 			break;
 		case OR:
@@ -267,8 +253,7 @@ public class OperatorTypeMap {
 		case ANY:
 			break;
 		case BEGINS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextBeginsWith(columnReference,new C_ConstantList(arguments));
+			exp=new C_TextBeginsWith(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case BETWEEN:
 			fArg=new TD_Value(dataType,firstArg);
@@ -304,23 +289,19 @@ public class OperatorTypeMap {
 		case DIVISION:
 			break;
 		case ENDS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextEndsWith(columnReference,new C_ConstantList(arguments));
+			exp=new C_TextEndsWith(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_Equals(columnReference,new C_ConstantList(arguments));
+			exp=new C_Equals(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case EXISTS:
 			//exp=new C_Exi(placeHolder,new C_ConstantList(arguments));
 			break;
 		case GREATER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_GreaterThan(columnReference,new C_ConstantList(arguments));
+			exp=new C_GreaterThan(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case GREATER_OR_EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_GreaterOrEquals(columnReference,new C_ConstantList(arguments));
+			exp=new C_GreaterOrEquals(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case IN:
 			break;
@@ -331,18 +312,15 @@ public class OperatorTypeMap {
 			exp=new C_IsNull(columnReference);
 			break;
 		case LESSER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_LessThan(columnReference,new C_ConstantList(arguments));
+			exp=new C_LessThan(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case LESSER_OR_EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_LessOrEquals(columnReference,new C_ConstantList(arguments));	
+			exp=new C_LessOrEquals(columnReference,new TD_Value(dataType,firstArg));	
 			break;
 		case LIKE:
 			break;
 		case MATCH_REGEX:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextMatchSQLRegexp(columnReference,new C_ConstantList(arguments));
+			exp=new C_TextMatchSQLRegexp(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case MODULUS:
 			break;
@@ -351,8 +329,7 @@ public class OperatorTypeMap {
 		case NOT:
 			break;
 		case NOT_BEGINS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextBeginsWith(columnReference,new C_ConstantList(arguments));
+			exp=new C_TextBeginsWith(columnReference,new TD_Value(dataType,firstArg));
 			exp=new C_Not(exp);
 			break;
 		case NOT_BETWEEN:
@@ -389,29 +366,24 @@ public class OperatorTypeMap {
 			exp=new C_Not(exp);
 			break;
 		case NOT_ENDS_WITH:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextEndsWith(columnReference,new C_ConstantList(arguments));
+			exp=new C_TextEndsWith(columnReference,new TD_Value(dataType,firstArg));
 			exp=new C_Not(exp);
 			break;
 		case NOT_EQUALS:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_NotEquals(columnReference,new C_ConstantList(arguments));
+			exp=new C_NotEquals(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case NOT_GREATER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_NotGreater(columnReference,new C_ConstantList(arguments));
+			exp=new C_NotGreater(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case NOT_IN:
 			break;
 		case NOT_LESSER:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_NotLess(columnReference,new C_ConstantList(arguments));
+			exp=new C_NotLess(columnReference,new TD_Value(dataType,firstArg));
 			break;
 		case NOT_LIKE:
 			break;
 		case NOT_MATCH_REGEX:
-			arguments.add(new TD_Value(dataType,firstArg));
-			exp=new C_TextMatchSQLRegexp(columnReference,new C_ConstantList(arguments));
+			exp=new C_TextMatchSQLRegexp(columnReference,new TD_Value(dataType,firstArg));
 			exp=new C_Not(exp);
 			break;
 		case OR:
diff --git a/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/leaf/TD_Value.java b/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/leaf/TD_Value.java
index 75b8e2b..505abb0 100644
--- a/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/leaf/TD_Value.java
+++ b/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/model/leaf/TD_Value.java
@@ -1,10 +1,8 @@
 package org.gcube.portlets.user.td.expressionwidget.shared.model.leaf;
 
-import java.io.Serializable;
-
 import org.gcube.portlets.user.td.widgetcommonevent.shared.tr.column.ColumnDataType;
 
-public class TD_Value implements Serializable {
+public class TD_Value extends C_Leaf {
 
 	private static final long serialVersionUID = 2802022467528178596L;
 	protected String id="TD_Value";