private function checkAsset($name, array &$previously)
{
$formula = $this->am->hasFormula($name) ? serialize($this->am->getFormula($name)) : null;
$asset = $this->am->get($name);
$mtime = $asset->getLastModified();
if (isset($previously[$name])) {
$changed = $previously[$name]['mtime'] != $mtime || $previously[$name]['formula'] != $formula;
} else {
$changed = true;
}
$previously[$name] = array('mtime' => $mtime, 'formula' => $formula);
return $changed;
}