code: public String getPolicy(String url, Date captureDate, Date retrievalDate,
              String who) throws RobotsUnavailableException, 
                                 RuleOracleUnavailableException {
          return getPolicy(url, getRule(url, captureDate, retrievalDate, who));
      }
docs: Return the best-matching policy for the requested document.
  
  @param url
  URL of the requested document.
  @param captureDate
  Date the document was archived.
  @param retrievalDate
  Date of retrieval (usually now).
  @param who
  Group name of the user accessing the document.
  @return Access-control policy that should be enforced. eg "robots",
  "block" or "allow".
  @throws RobotsUnavailableException
  @throws RuleOracleUnavailableException