public function children($lang='',$alias=''){
		$collname=$this->collectionName;
		$bitems=$collname::GetInstance();
		$children=$bitems->itemsFilter(array('parent'=>$this->id));
		if(empty($alias)){
			return $children;
			}
		foreach($children as $ch){
			$chalias=$ch->getalias($lang);
			if($chalias==$alias){
				return $ch;
				}
			}
		return NULL;
		}