protected function bootstrapAlert($content, $dismissible, $class) {

        $span   = static::coreHTMLElement("span", "&times;", ["aria-hidden" => "true"]);
        $button = static::coreHTMLElement("button", $span, ["class" => "close", "type" => "button", "data-dismiss" => "alert", "aria-label" => "Close"]);

        $attributes = [];

        $attributes["class"]   = ["alert", $class];
        $attributes["class"][] = true === $dismissible ? "alert-dismissible" : null;
        $attributes["role"]    = ["alert"];

        $innerHTML = (true === $dismissible ? $button : "") . (null !== $content ? $content : "");

        return static::coreHTMLElement("div", $innerHTML, $attributes);
    }