/**
   * Build the resource map from the KML Model's <i>ResourceMap</i> element.
   *
   * @param model Model from which to create the resource map.
   * @return Map that relates relative paths in the COLLADA document to paths relative to the KML
   *     document.
   */
  protected Map<String, String> createResourceMap(KMLModel model) {
    Map<String, String> map = new HashMap<String, String>();

    KMLResourceMap resourceMap = model.getResourceMap();
    if (resourceMap == null) return Collections.emptyMap();

    for (KMLAlias alias : resourceMap.getAliases()) {
      if (alias != null
          && !WWUtil.isEmpty(alias.getSourceRef())
          && !WWUtil.isEmpty(alias.getTargetHref())) {
        map.put(alias.getSourceRef(), alias.getTargetHref());
      }
    }

    return map.size() > 0 ? map : Collections.<String, String>emptyMap();
  }
  /**
   * Determines and stores the network sites to test for public network connectivity. The sites are
   * drawn from the JVM's gov.nasa.worldwind.avkey.NetworkStatusTestSites property ({@link
   * AVKey#NETWORK_STATUS_TEST_SITES}). If that property is not defined, the sites are drawn from
   * the same property in the World Wind or application configuration file. If the sites are not
   * specified there, the set of sites specified in {@link #DEFAULT_NETWORK_TEST_SITES} are used. To
   * indicate an empty list in the JVM property or configuration file property, specify an empty
   * site list, "".
   */
  protected void establishNetworkTestSites() {
    String testSites = System.getProperty(AVKey.NETWORK_STATUS_TEST_SITES);

    if (testSites == null)
      testSites = Configuration.getStringValue(AVKey.NETWORK_STATUS_TEST_SITES);

    if (testSites == null) {
      this.networkTestSites.addAll(Arrays.asList(DEFAULT_NETWORK_TEST_SITES));
    } else {
      String[] sites = testSites.split(",");
      List<String> actualSites = new ArrayList<String>(sites.length);

      for (String site : sites) {
        site = WWUtil.removeWhiteSpace(site);
        if (!WWUtil.isEmpty(site)) actualSites.add(site);
      }

      this.setNetworkTestSites(actualSites);
    }
  }
  /**
   * Thread's off a task to determine whether the resource is local or remote and then retrieves it
   * either from disk cache or a remote server.
   *
   * @param dc the current draw context.
   */
  protected void requestResource(DrawContext dc) {
    if (WorldWind.getTaskService().isFull()) return;

    KMLLink link = this.model.getLink();
    if (link == null) return;

    String address = link.getAddress(dc);
    if (address != null) address = address.trim();

    if (WWUtil.isEmpty(address)) return;

    WorldWind.getTaskService().addTask(new RequestTask(this, address));
  }