private Object evaluateExpression(Node<?> context, Node<?> thisNode, String expr)
     throws InvalidExpressionException {
   ExpressionFactory expressionFactory =
       context.getRecord().getSurveyContext().getExpressionFactory();
   DefaultValueExpression expression = expressionFactory.createDefaultValueExpression(expr);
   Object object = expression.evaluate(context, thisNode);
   return object;
 }