=== modified file 'dhis-2/dhis-api/src/main/java/org/hisp/dhis/dataset/DataSet.java'
--- dhis-2/dhis-api/src/main/java/org/hisp/dhis/dataset/DataSet.java	2011-05-30 14:56:19 +0000
+++ dhis-2/dhis-api/src/main/java/org/hisp/dhis/dataset/DataSet.java	2011-05-30 15:17:51 +0000
@@ -27,7 +27,6 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-import java.util.Collection;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -62,7 +61,7 @@
     /**
      * All DataElements associated with this DataSet.
      */
-    private Collection<DataElement> dataElements = new HashSet<DataElement>();
+    private Set<DataElement> dataElements = new HashSet<DataElement>();
 
     /**
      * Indicators associated with this data set. Indicators are used for view and
@@ -177,6 +176,34 @@
         }
     }
     
+    public void addDataElement( DataElement dataElement )
+    {
+        dataElements.add( dataElement );
+        dataElement.getDataSets().add( this );
+    }
+    
+    public void removeDataElement( DataElement dataElement )
+    {
+        dataElements.remove( dataElement );
+        dataElement.getDataSets().remove( dataElement );
+    }
+    
+    public void updateDataElements( Set<DataElement> updates )
+    {
+        for ( DataElement dataElement : new HashSet<DataElement>( dataElements ) )
+        {
+            if ( !updates.contains( dataElement ) )
+            {
+                removeDataElement( dataElement );
+            }
+        }
+        
+        for ( DataElement dataElement : updates )
+        {
+            addDataElement( dataElement );
+        }
+    }
+    
     public boolean hasDataEntryForm()
     {
         return dataEntryForm != null;
@@ -255,12 +282,12 @@
         this.periodType = periodType;
     }
 
-    public Collection<DataElement> getDataElements()
+    public Set<DataElement> getDataElements()
     {
         return dataElements;
     }
 
-    public void setDataElements( Collection<DataElement> dataElements )
+    public void setDataElements( Set<DataElement> dataElements )
     {
         this.dataElements = dataElements;
     }

=== modified file 'dhis-2/dhis-services/dhis-service-administration/src/test/java/org/hisp/dhis/dataarchive/DataArchiveTest.java'
--- dhis-2/dhis-services/dhis-service-administration/src/test/java/org/hisp/dhis/dataarchive/DataArchiveTest.java	2010-10-01 09:05:32 +0000
+++ dhis-2/dhis-services/dhis-service-administration/src/test/java/org/hisp/dhis/dataarchive/DataArchiveTest.java	2011-05-30 15:17:51 +0000
@@ -31,6 +31,7 @@
 import java.util.Date;
 import java.util.HashSet;
 import java.util.Iterator;
+import java.util.Set;
 
 import org.hisp.dhis.DhisTest;
 import org.hisp.dhis.dataelement.DataElement;
@@ -174,9 +175,9 @@
         dataElementIds.add( dataElementService.addDataElement( dataElementE ) );
         dataElementIds.add( dataElementService.addDataElement( dataElementF ) );
 
-        Collection<DataElement> dataElementsA = new HashSet<DataElement>();
-        Collection<DataElement> dataElementsB = new HashSet<DataElement>();
-        Collection<DataElement> dataElementsC = new HashSet<DataElement>();
+        Set<DataElement> dataElementsA = new HashSet<DataElement>();
+        Set<DataElement> dataElementsB = new HashSet<DataElement>();
+        Set<DataElement> dataElementsC = new HashSet<DataElement>();
 
         // One dataElement
         dataElementsA.add( dataElementA );

=== modified file 'dhis-2/dhis-services/dhis-service-administration/src/test/java/org/hisp/dhis/databrowser/DataBrowserTest.java'
--- dhis-2/dhis-services/dhis-service-administration/src/test/java/org/hisp/dhis/databrowser/DataBrowserTest.java	2011-03-14 09:16:45 +0000
+++ dhis-2/dhis-services/dhis-service-administration/src/test/java/org/hisp/dhis/databrowser/DataBrowserTest.java	2011-05-30 15:17:51 +0000
@@ -174,9 +174,9 @@
         dataElementIds.add( dataElementService.addDataElement( dataElementE ) );
         dataElementIds.add( dataElementService.addDataElement( dataElementF ) );
 
-        Collection<DataElement> dataElementsA = new HashSet<DataElement>();
-        Collection<DataElement> dataElementsB = new HashSet<DataElement>();
-        Collection<DataElement> dataElementsC = new HashSet<DataElement>();
+        Set<DataElement> dataElementsA = new HashSet<DataElement>();
+        Set<DataElement> dataElementsB = new HashSet<DataElement>();
+        Set<DataElement> dataElementsC = new HashSet<DataElement>();
 
         // One dataElement
         dataElementsA.add( dataElementA );

=== modified file 'dhis-2/dhis-web/dhis-web-maintenance/dhis-web-maintenance-dataset/src/main/java/org/hisp/dhis/dataset/action/AddDataSetAction.java'
--- dhis-2/dhis-web/dhis-web-maintenance/dhis-web-maintenance-dataset/src/main/java/org/hisp/dhis/dataset/action/AddDataSetAction.java	2011-05-28 21:53:18 +0000
+++ dhis-2/dhis-web/dhis-web-maintenance/dhis-web-maintenance-dataset/src/main/java/org/hisp/dhis/dataset/action/AddDataSetAction.java	2011-05-30 15:17:51 +0000
@@ -31,7 +31,6 @@
 import java.util.HashSet;
 import java.util.Set;
 
-import org.hisp.dhis.dataelement.DataElement;
 import org.hisp.dhis.dataelement.DataElementService;
 import org.hisp.dhis.dataset.DataSet;
 import org.hisp.dhis.dataset.DataSetService;
@@ -165,11 +164,11 @@
 
         PeriodType periodType = periodService.getPeriodTypeByName( frequencySelect );
 
-        Collection<DataElement> dataElements = new HashSet<DataElement>();
+        DataSet dataSet = new DataSet( name, shortName, code, periodType );
 
         for ( String id : dataElementsSelectedList )
         {
-            dataElements.add( dataElementService.getDataElement( Integer.parseInt( id ) ) );
+            dataSet.addDataElement( dataElementService.getDataElement( Integer.parseInt( id ) ) );
         }
 
         Set<Indicator> indicators = new HashSet<Indicator>();
@@ -179,11 +178,8 @@
             indicators.add( indicatorService.getIndicator( Integer.parseInt( id ) ) );
         }
 
-        DataSet dataSet = new DataSet( name, shortName, code, periodType );
-
         dataSet.setMobile( mobile );
         dataSet.setVersion( 1 );
-        dataSet.setDataElements( dataElements );
         dataSet.setIndicators( indicators );
 
         dataSetService.addDataSet( dataSet );

=== modified file 'dhis-2/dhis-web/dhis-web-maintenance/dhis-web-maintenance-dataset/src/main/java/org/hisp/dhis/dataset/action/UpdateDataSetAction.java'
--- dhis-2/dhis-web/dhis-web-maintenance/dhis-web-maintenance-dataset/src/main/java/org/hisp/dhis/dataset/action/UpdateDataSetAction.java	2011-05-28 21:53:18 +0000
+++ dhis-2/dhis-web/dhis-web-maintenance/dhis-web-maintenance-dataset/src/main/java/org/hisp/dhis/dataset/action/UpdateDataSetAction.java	2011-05-30 15:17:51 +0000
@@ -155,7 +155,7 @@
             code = null;
         }
 
-        Collection<DataElement> dataElements = new HashSet<DataElement>();
+        Set<DataElement> dataElements = new HashSet<DataElement>();
 
         for ( String id : dataElementsSelectedList )
         {
@@ -177,7 +177,7 @@
         dataSet.setShortName( shortName );
         dataSet.setCode( code );
         dataSet.setPeriodType( periodService.getPeriodTypeByClass( periodType.getClass() ) );
-        dataSet.setDataElements( dataElements );
+        dataSet.updateDataElements( dataElements );
         dataSet.setIndicators( indicators );
 
         if ( dataSet.isMobile() )