The goal of Unidata's Thematic Real-time Environmental Distributed Data Services (THREDDS) is to provide students, educators and researchers with coherent access to a large collection of real-time and archived datasets from a variety of environmental data sources at a number of distributed server sites.

The THREDDS Data Server (TDS) is a web server that provides catalog, metadata, and data access services for scientific data. Every TDS publishes THREDDS catalogs that advertise the datasets and services it makes available. THREDDS catalogs are XML documents that list datasets and the data access services available for the datasets. Catalogs may contain metadata to document details about the datasets. TDS configuration files provide the TDS with information about which datasets and data collections are available and what services are provided for the datasets. The available remote data access protocols include OPeNDAP, OGC WCS, OGC WMS, and HTTP. The ncISO service allows THREDDS catalogs to be translated into ISO metadata records. The TDS also supports several dataset collection services including some sophisticated dataset aggregation capabilities. This allows the TDS to aggregate a collection of datasets into a single virtual dataset, greatly simplifying user access to that data collection.

The TDS is open source and runs inside the open-source Tomcat Servlet container. The TDS is developed and supported by Unidata, a division of the University Corporation for Atmospheric Research (UCAR), and is sponsored by the National Science Foundation.

The Unidata Local Data Manager (LDM) is a collection of cooperating programs that select, capture, manage, and distribute arbitrary data products. The system is designed for event-driven data distribution of the kind used in the Unidata Internet Data Distribution (IDD) project. LDM system includes network client and server programs designed for event-driven data distribution and is the fundamental component comprising the IDD system.

• From the user's perspective, one should be able to retrieve data and:
  • Obtain information regarding the dataset, without the need to download any files:
    • Temporal spatial ranges, available variables, contact info, dataset details.
  • Retrieve user-relevant subset of the data (temporal, spatial, and variable subsetting).
  • Get data remotely in a variety of ways, including:
    • OPeNDAP (DAP2/DAP4) protocol.
    • ncWMS implementing the Web Map Service.
    • Web Coverage Service.
    • ncISO.
    • NetCDF Subset Services.
  • Download one file, even if data span multiple files.
• From the data provider's perspective, one should be able to provide data and:
  • Catalog data holdings.
  • Aggregate data files.
  • Provide a quick view of data.
  • Easily add information (metadata) to datasets.