Main algorithm

1. Input options and necessary data (from command line)
2. Start recursive URL retrieval algorithm

      retrieveData(URL, maxDepth, Graph) {
        get current timestamp;
        store timestamp in graph
        retrieveData(URL, maxDepth, Graph, 0);
      }
      store graph on disk
      
      retrieveData(URL, maxDepth, Graph, currentDepth) {
        if (currentDepth < maxDepth) {
          retrieve URL;
          parse HTML, get list of sub-URLs;
          for each sub-URL in list {
            store arc (URL, sub-URL) in graph
            retrieveData(sub-URL, maxDepth, graph, currentDepth + 1);
          }
        }
      }