Bug 145022 Provide a utility method to help GUI enhance aggregate on.
DtE will provide a method hasAggregation(String expression) in org.eclipse.birt.core.data.ExpressionUtil, and the return value will be true when the expression is a valid JS expression and it has aggregation defined.
core/org.eclipse.birt.core/src/org/eclipse/birt/core/data/ExpressionParserUtility.java
Node rowColumn = rowFirstNode.getNext( );
				if ( rowColumn.getType( ) == Token.STRING )
				{
					if ( "_outer".equals( rowColumn.getString( ) ) )
						count++;
				}
				return count;
			}
			else if ( rowFirstNode.getType( ) == Token.GETPROP )
			{
				if ( compileOuterColRefExpr( rowFirstNode ) == -1 )
					return -1;
				else
					count = count + compileOuterColRefExpr( rowFirstNode );
				Node nextChild = rowFirstNode.getNext( );
				if ( nextChild.getType( ) == Token.STRING )
				{
					if ( "_outer".equals( nextChild.getString( ) ) )
						count++;
				}
			}
			else
				return -1;
			return count;
		}
		else
			return -1;
	}
	/**
	 * compile aggregate expression