public static List<String> query(String[] keywords)
	{
		List<String> url = new ArrayList<String>();
		//Map<String, head> head;
		//scan if in the cache
		for(int i=0; i<keywords.length; i++)
		{
			//offset = check_in_cache();
			//maintain cache
		}
		//scan if in the lexicon
		for(int i=0; i<keywords.length; i++)
		{
			//offset = check_in_lexicon();
			
			
			//maintain cache
		}
		
		
		for (int i=0;i<keywords.length;i++){
			
		}
		//
		/*
		 * Map<DocID, score> TAAT;
		 * while(head.getValue(words[0]).hasNext())
		 * {
		 * 		//uncompress every DocID in head[0]
		 *      //check whether the other words in the DocID
		 *         use DAAT with chunkwise
		 *      if(true)
		 *      {
		 *      	double bm =  BM25;
		 *          TAAT.put(DocID, bm);
		 *      }
		 *      else
		 *        next;
		 * }
		 * TAAT.sort();
		 * if(TAAT.size>= 10)
		 * {
		 * 		for(int i=0; i<10; i++)
		 * 			url.add(TAAT.geturl);
		 * }
		*/
		
		return url;
		
	}