=== modified file 'dhis-2/dhis-services/dhis-service-aggregationengine-default/src/main/java/org/hisp/dhis/aggregation/impl/indicator/IndicatorAggregation.java'
--- dhis-2/dhis-services/dhis-service-aggregationengine-default/src/main/java/org/hisp/dhis/aggregation/impl/indicator/IndicatorAggregation.java	2010-12-06 21:06:40 +0000
+++ dhis-2/dhis-services/dhis-service-aggregationengine-default/src/main/java/org/hisp/dhis/aggregation/impl/indicator/IndicatorAggregation.java	2011-05-20 13:18:16 +0000
@@ -33,8 +33,9 @@
 import static org.hisp.dhis.system.util.MathUtils.calculateExpression;
 
 import java.util.Date;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
 
 import org.hisp.dhis.aggregation.impl.cache.AggregationCache;
 import org.hisp.dhis.dataelement.DataElement;
@@ -52,8 +53,6 @@
  */
 public class IndicatorAggregation
 {
-    private static final Pattern FORMULA_PATTERN = Pattern.compile( ExpressionService.FORMULA_EXPRESSION );
-    
     // -------------------------------------------------------------------------
     // Dependencies
     // -------------------------------------------------------------------------
@@ -71,6 +70,13 @@
     {
         this.dataElementService = dataElementService;
     }
+
+    private ExpressionService expressionService;
+
+    public void setExpressionService( ExpressionService expressionService )
+    {
+        this.expressionService = expressionService;
+    }
     
     private DataElementCategoryService categoryService;
 
@@ -143,46 +149,20 @@
         return factor;
     }
     
-    /**
-     * Converts an expression on the form<br>
-     * [34] + [23], where the numbers are IDs of DataElements, to the form<br>
-     * 200 + 450, where the numbers are the values of the DataValues registered
-     * for the Period and source.
-     * 
-     * @return The generated expression
-     */
-    private String generateExpression( String formula, Date startDate, Date endDate, OrganisationUnit organisationUnit )
-    {    	
-        try
-        {        	
-            Matcher matcher = FORMULA_PATTERN.matcher( formula );
-            
-            StringBuffer buffer = new StringBuffer();            
-            
-            while ( matcher.find() )
-            {
-                String match = matcher.group();
-                
-                DataElementOperand operand = DataElementOperand.getOperand( match );
-                
-                DataElement dataElement = dataElementService.getDataElement( operand.getDataElementId() );
-                
-                DataElementCategoryOptionCombo optionCombo = !operand.isTotal() ? categoryService.getDataElementCategoryOptionCombo( operand.getOptionComboId() ) : null;
-
-                Double aggregatedValue = aggregationCache.getAggregatedDataValue( dataElement, optionCombo, startDate, endDate, organisationUnit );   
-                
-                match = aggregatedValue == null ? ExpressionService.NULL_REPLACEMENT : String.valueOf( aggregatedValue );
-                
-                matcher.appendReplacement( buffer, match );
-            }
-
-            matcher.appendTail( buffer );
-
-            return buffer.toString();
-        }
-        catch ( NumberFormatException ex )
+    private String generateExpression( String expression, Date startDate, Date endDate, OrganisationUnit organisationUnit )
+    {
+        Set<DataElementOperand> operands = expressionService.getOperandsInExpression( expression );
+        
+        Map<DataElementOperand, Double> valueMap = new HashMap<DataElementOperand, Double>();
+        
+        for ( DataElementOperand operand : operands )
         {
-            throw new RuntimeException( "Illegal DataElement id", ex );
+            DataElement dataElement = dataElementService.getDataElement( operand.getDataElementId() );
+            DataElementCategoryOptionCombo optionCombo = !operand.isTotal() ? categoryService.getDataElementCategoryOptionCombo( operand.getOptionComboId() ) : null;
+
+            valueMap.put( operand, aggregationCache.getAggregatedDataValue( dataElement, optionCombo, startDate, endDate, organisationUnit ) );            
         }
+        
+        return expressionService.generateExpression( expression, valueMap );
     }
 }

=== modified file 'dhis-2/dhis-services/dhis-service-aggregationengine-default/src/main/resources/META-INF/dhis/beans.xml'
--- dhis-2/dhis-services/dhis-service-aggregationengine-default/src/main/resources/META-INF/dhis/beans.xml	2010-07-04 11:50:16 +0000
+++ dhis-2/dhis-services/dhis-service-aggregationengine-default/src/main/resources/META-INF/dhis/beans.xml	2011-05-20 13:18:16 +0000
@@ -87,6 +87,8 @@
 		ref="org.hisp.dhis.dataelement.DataElementService"/>
 	<property name="categoryService"
 		ref="org.hisp.dhis.dataelement.DataElementCategoryService"/>
+	<property name="expressionService"
+		ref="org.hisp.dhis.expression.ExpressionService"/>
 	<property name="aggregationCache"
         ref="org.hisp.dhis.aggregation.impl.cache.AggregationCache"/>    
   </bean>