diff --git a/src/main/java/org/gcube/accounting/datamodel/AggregatedUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/AggregatedUsageRecord.java
new file mode 100644
index 0000000..18f0e44
--- /dev/null
+++ b/src/main/java/org/gcube/accounting/datamodel/AggregatedUsageRecord.java
@@ -0,0 +1,28 @@
+/**
+ * 
+ */
+package org.gcube.accounting.datamodel;
+
+import org.gcube.accounting.exception.InvalidValueException;
+
+/**
+ * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
+ */
+public interface AggregatedUsageRecord extends UsageRecord {
+	
+	/**
+	 * Return the id of the usage record aggregating this
+	 * @return Aggregated Id
+	 */
+	@Override
+	public String getAggregatedId();
+
+	/**
+	 * Set the id of the usage record aggregating this
+	 * @param aggregatedId
+	 * @throws InvalidValueException
+	 */
+	@Override
+	public void setAggregatedId(String aggregatedId) throws InvalidValueException;
+	
+}
diff --git a/src/main/java/org/gcube/accounting/datamodel/SingleUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/SingleUsageRecord.java
new file mode 100644
index 0000000..d6349f4
--- /dev/null
+++ b/src/main/java/org/gcube/accounting/datamodel/SingleUsageRecord.java
@@ -0,0 +1,12 @@
+/**
+ * 
+ */
+package org.gcube.accounting.datamodel;
+
+/**
+ * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
+ *
+ */
+public interface SingleUsageRecord extends UsageRecord {
+
+}
diff --git a/src/main/java/org/gcube/accounting/datamodel/implementations/JobUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/implementations/JobUsageRecord.java
index b480807..c63eb32 100644
--- a/src/main/java/org/gcube/accounting/datamodel/implementations/JobUsageRecord.java
+++ b/src/main/java/org/gcube/accounting/datamodel/implementations/JobUsageRecord.java
@@ -6,6 +6,7 @@ package org.gcube.accounting.datamodel.implementations;
 import java.util.Calendar;
 
 import org.gcube.accounting.datamodel.RawUsageRecord;
+import org.gcube.accounting.datamodel.SingleUsageRecord;
 import org.gcube.accounting.datamodel.annotations.NotEmpty;
 import org.gcube.accounting.datamodel.annotations.ValidInteger;
 import org.gcube.accounting.datamodel.annotations.ValidLong;
@@ -15,7 +16,7 @@ import org.gcube.accounting.exception.InvalidValueException;
  * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
  *
  */
-public class JobUsageRecord extends RawUsageRecord {
+public class JobUsageRecord extends RawUsageRecord implements SingleUsageRecord {
 
 	/**
 	 * Generated Serial Version UID
diff --git a/src/main/java/org/gcube/accounting/datamodel/implementations/PortletUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/implementations/PortletUsageRecord.java
index d19e927..b7155d7 100644
--- a/src/main/java/org/gcube/accounting/datamodel/implementations/PortletUsageRecord.java
+++ b/src/main/java/org/gcube/accounting/datamodel/implementations/PortletUsageRecord.java
@@ -4,6 +4,7 @@
 package org.gcube.accounting.datamodel.implementations;
 
 import org.gcube.accounting.datamodel.RawUsageRecord;
+import org.gcube.accounting.datamodel.SingleUsageRecord;
 import org.gcube.accounting.datamodel.annotations.NotEmpty;
 import org.gcube.accounting.exception.InvalidValueException;
 
@@ -11,7 +12,7 @@ import org.gcube.accounting.exception.InvalidValueException;
  * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
  *
  */
-public class PortletUsageRecord extends RawUsageRecord {
+public class PortletUsageRecord extends RawUsageRecord implements SingleUsageRecord {
 
 	/**
 	 * Generated Serial Version UID
diff --git a/src/main/java/org/gcube/accounting/datamodel/implementations/ServiceUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/implementations/ServiceUsageRecord.java
index 17d2fff..e6a1ff6 100644
--- a/src/main/java/org/gcube/accounting/datamodel/implementations/ServiceUsageRecord.java
+++ b/src/main/java/org/gcube/accounting/datamodel/implementations/ServiceUsageRecord.java
@@ -4,6 +4,7 @@
 package org.gcube.accounting.datamodel.implementations;
 
 import org.gcube.accounting.datamodel.RawUsageRecord;
+import org.gcube.accounting.datamodel.SingleUsageRecord;
 import org.gcube.accounting.datamodel.annotations.NotEmpty;
 import org.gcube.accounting.datamodel.annotations.ValidIP;
 import org.gcube.accounting.datamodel.annotations.ValidInteger;
@@ -13,7 +14,7 @@ import org.gcube.accounting.exception.InvalidValueException;
  * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
  *
  */
-public class ServiceUsageRecord extends RawUsageRecord {
+public class ServiceUsageRecord extends RawUsageRecord implements SingleUsageRecord {
 
 	/**
 	 * Generated Serial Version UID
diff --git a/src/main/java/org/gcube/accounting/datamodel/implementations/StorageUsageUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/implementations/StorageUsageUsageRecord.java
index 2f2769a..0043870 100644
--- a/src/main/java/org/gcube/accounting/datamodel/implementations/StorageUsageUsageRecord.java
+++ b/src/main/java/org/gcube/accounting/datamodel/implementations/StorageUsageUsageRecord.java
@@ -3,19 +3,20 @@
  */
 package org.gcube.accounting.datamodel.implementations;
 
-import org.gcube.accounting.datamodel.aggregated.StorageStatusUsageRecord;
+import org.gcube.accounting.datamodel.SingleUsageRecord;
 import org.gcube.accounting.datamodel.annotations.NotEmpty;
 import org.gcube.accounting.datamodel.annotations.NotEmptyIfNotNull;
 import org.gcube.accounting.datamodel.annotations.ValidIP;
 import org.gcube.accounting.datamodel.annotations.ValidInteger;
 import org.gcube.accounting.datamodel.annotations.ValidLong;
+import org.gcube.accounting.datamodel.implementations.aggregated.StorageStatusUsageRecord;
 import org.gcube.accounting.exception.InvalidValueException;
 
 /**
  * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
  *
  */
-public class StorageUsageUsageRecord extends StorageStatusUsageRecord {
+public class StorageUsageUsageRecord extends StorageStatusUsageRecord implements SingleUsageRecord {
 
 	/**
 	 * Generated Serial Version UID
diff --git a/src/main/java/org/gcube/accounting/datamodel/implementations/TaskUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/implementations/TaskUsageRecord.java
index 3215f9f..bd5a016 100644
--- a/src/main/java/org/gcube/accounting/datamodel/implementations/TaskUsageRecord.java
+++ b/src/main/java/org/gcube/accounting/datamodel/implementations/TaskUsageRecord.java
@@ -6,6 +6,7 @@ package org.gcube.accounting.datamodel.implementations;
 import java.util.Calendar;
 
 import org.gcube.accounting.datamodel.RawUsageRecord;
+import org.gcube.accounting.datamodel.SingleUsageRecord;
 import org.gcube.accounting.datamodel.annotations.NotEmpty;
 import org.gcube.accounting.datamodel.annotations.ValidInteger;
 import org.gcube.accounting.datamodel.annotations.ValidLong;
@@ -15,7 +16,7 @@ import org.gcube.accounting.exception.InvalidValueException;
  * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
  *
  */
-public class TaskUsageRecord extends RawUsageRecord {
+public class TaskUsageRecord extends RawUsageRecord implements SingleUsageRecord {
 
 	/**
 	 * Generated Serial Version UID
diff --git a/src/main/java/org/gcube/accounting/datamodel/aggregated/StorageStatusUsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/implementations/aggregated/StorageStatusUsageRecord.java
similarity index 96%
rename from src/main/java/org/gcube/accounting/datamodel/aggregated/StorageStatusUsageRecord.java
rename to src/main/java/org/gcube/accounting/datamodel/implementations/aggregated/StorageStatusUsageRecord.java
index 0ee0607..c71a46d 100644
--- a/src/main/java/org/gcube/accounting/datamodel/aggregated/StorageStatusUsageRecord.java
+++ b/src/main/java/org/gcube/accounting/datamodel/implementations/aggregated/StorageStatusUsageRecord.java
@@ -1,7 +1,7 @@
 /**
  * 
  */
-package org.gcube.accounting.datamodel.aggregated;
+package org.gcube.accounting.datamodel.implementations.aggregated;
 
 import org.gcube.accounting.datamodel.RawUsageRecord;
 import org.gcube.accounting.datamodel.annotations.NotEmpty;
@@ -11,7 +11,6 @@ import org.gcube.accounting.exception.InvalidValueException;
 
 /**
  * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
- *
  */
 public class StorageStatusUsageRecord extends RawUsageRecord {