THREDDS Catalogs are logical directories of on-line data resources, encoded as XML documents, which provide a place for annotations and other metadata about the data resources to reside. This is how THREDDS-enabled data consumers find out what data is available from data providers.
THREDDS Catalogs were originally designed for clients to use to access remote data. They have been extended to allow the TDS to use them for its own configuration. In this mode they are called TDS Configuration Catalogs, or server-side Catalogs. They contain information needed only on the server, which is removed when the TDS sends the catalog to the client, called the client-side or client-view catalog.
For client-side catalogs, the current specifications are:
The Java NetCDF library has a complete package (thredds.catalog) to parse client-side catalogs. A newer package (thredds.catalog2) is scheduled for release in version 4.3.
The TDS dynamically generates THREDDS catalogs based on the TDS configuration catalogs. For server-side catalogs, the current specifications are: