public static ArrayList<InveList> retrieval (String nodeName) throws IOException {
		//get inveted list for certain query term from local file
		ArrayList<InveList> retrievalResult = new ArrayList<InveList>();
		String filePath = System.getProperty("user.dir") + "\\clueweb09_wikipedia_15p_invLists\\" + nodeName +".inv";

		BufferedReader br = null;
		try {
			br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath)));
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			return null;
		}

		String line = br.readLine();
		line = br.readLine();
		if (line == null)
			return retrievalResult;

		//get every inverted list item and store it into the InveList structure
        for (; line != null; line = br.readLine()) {
        	String[] para = line.split(" ");
        	InveList temp= new InveList();

        	temp.setDocID(Integer.parseInt(para[0]));
        	temp.setTf(Integer.parseInt(para[1]));
        	temp.setDocLen(Integer.parseInt(para[2]));
        	for (int i = 3; i < temp.getTf() + 3; i++)
        		temp.Pos.add(Integer.parseInt(para[i]));

        	retrievalResult.add(temp);
        }
        br.close();

		return retrievalResult;
	}