public function registerAt($step, $method, $args, $action)
    {
        $args   = $this->replaceWildcards($args);
        $method = strtolower($method);
        if (! isset($this->at[$method])) {
            $this->at[$method] = array();
        }
        if (! isset($this->at[$method][$step])) {
            $this->at[$method][$step] = new SimpleSignatureMap();
        }
        $this->at[$method][$step]->add($args, $action);
    }