protected function processArgumentBoolean(Element $arg) {
		$definition = new stdClass();
		$definition->type = 'value';
		
		if (isset($arg->value)) {
			$definition->value = (trim($arg->value) === 'true');
			return $definition;
		}
		
		$value = $arg->getValue();
		
		if (! empty($value)) {
			$definition->value = (trim($value) === 'true');
			return $definition;
		}
		
		throw new InvalidConfig('Definition of an argument type "boolean" must contain a value as content or the "value" attribute', null, null, $arg);
	}