public function getValues()
 {
     $formValues = parent::getValues();
     $modelValues = array();
     foreach ($formValues as $formValue) {
         $expression = new ilAssQuestionSolutionComparisonExpression();
         $expression->setExpression($formValue->getAnswertext());
         $expression->setPoints($formValue->getPoints());
         $expression->setOrderIndex($formValue->getOrder() + 1);
         $modelValues[] = $expression;
     }
     return $modelValues;
 }