fsm contains objects that model files that are stored in a FileSystem with the filename parametric in time. For example, suppose there is a store of data in http://cdaweb.gsfc.nasa.gov/istp_public/data/ace/swe/, where the data files are stored by year and then in each yearly folder, the files contain the date encoded within the filename. We can then model the storage with the template specification %Y/ac_k0_swe_%Y%m%d_v01.cdf. A FileStorageModel object can be queried as to what is available for a time range, and will use the FileSystem object to provide local copies of the file. FileStorageModel is the production object providing this functionality. FileStorageModelNew is an attempt to unify codes by treating filenames as formatted time range strings, which should reduce code and run more efficiently. This code is not yet proven and should be used with caution. FileStorageModelAvailabilityDataSetDescriptor provides a DataSetDescriptor that can be used to get DataSet views describing when data is available.