code: private JSONObject getCriteriaFromWebDriverSelector(JSONObject payload) throws JSONException {
      String using = payload.getString("using");
      String value = payload.getString("value");
      if ("tag name".equals(using) || "class name".equals(using)) {
        try {
          Package p = UIAElement.class.getPackage();
          Criteria c = new TypeCriteria(Class.forName(p.getName() + "." + value));
          return c.stringify();
        } catch (ClassNotFoundException e) {
          throw new InvalidSelectorException(value + " is not a recognized type.");
        }
        //  http://developer.apple.com/library/ios/#documentation/uikit/reference/UIAccessibilityIdentification_Protocol/Introduction/Introduction.html
      } else if ("name".equals(using) || "id".equals(using)) {
        Criteria c = new NameCriteria(getAUT().applyL10N(value));
        return c.stringify();
      } else if ("link text".equals(using) || "partial link text".equals(using)) {
        return createGenericCriteria(using, value);
      } else {
        throw new InvalidSelectorException(
            using + "is not a valid selector for the native part of ios-driver.");
      }
    }
docs: handles the mapping from the webdriver using to a criteria.