cdm/src/main/java/thredds/inventory/MFileCollectionManager.java
static public MFileCollectionManager open(String collectionName, String collectionSpec, String olderThan, Formatter errlog) throws IOException {
    return new MFileCollectionManager(collectionName, collectionSpec, olderThan, errlog);
  }
static public MFileCollectionManager open(String collectionName, String collectionSpec, String olderThan, Formatter errlog) throws IOException {
    return new MFileCollectionManager(collectionName, collectionSpec, olderThan, errlog);
  }
called from Aggregation, Fmrc, FeatureDatasetFactoryManager