// retrieve already extracted THREDDS metadata
Metadata datasetMet = d.getDatasetMet(opendapUrl);
// extract DAS metadata
MetadataExtractor dasExtractor = new DasMetadataExtractor(dConn);
dasExtractor.extract(datasetMet, conf);
// extract NcML metadata, if available
if (datasetMet.containsKey(ThreddsMetadataExtractor.SERVICE_TYPE_NCML)) {
// retrieve URL of NcML document, previously stored
final String ncmlUrl = datasetMet.getMetadata(ThreddsMetadataExtractor.SERVICE_TYPE_NCML);