public function rules()
{
// NOTE: you should only define rules for those attributes that
// will receive user inputs.
return array(array('drug_set_id, drug_id', 'required'), array('dose, frequency_id, duration_id', 'safe'), array('id, drug_set_id, drug_id, dose, frequency_id, duration_id', 'safe', 'on' => 'search'));
}