2002 Annual

Wednesday, 16 January 2002
NASA's Global Change Master Directory's New Distributed Metadata Database Attracts Large Influx of Data Descriptions
Scott A. Ritz, SSAI, Lanham, MD
The Global Change Master (GCMD), http://gcmd.nasa.gov, is a database designed to assist scientists in locating Earth Science data sets. The GCMD provides over 10,000 data set descriptions of atmospheric, oceanographic, geologic, geographic, ecologic, and socioeconomic data holdings from around the world. The GCMD's latest release of its software (MD8) marks a clear change in the way the GCMD manages its meta-database. Prior to the release of MD8, new and modified metadata content was received by the GCMD manually either by e-mail, FTP, or through one of the online authoring tools. The GCMD's database administrator then loaded all content into the database. This practice worked well for many years, but as the number of the GCMD's cooperating partners and database content increased, it became crucial for the software to provide for distributed input and the automatic synchronization of metadata content. These features have spurred interest from many other groups.

The MD8 software provides participants with the tools to maintain a relational meta-database. The directory content is shared among the Committee on Earth Observation Satellites (CEOS) International Directory Network (IDN) partners. The GCMD serves as the American Coordinating node and is responsible for the IDN's software development. The GCMD also maintains the science keywords and controlled vocabulary.

Other international CEOS partners participate by providing content or by running "distributed nodes" of the directory. The metadata in each participating node's database is then automatically propagated throughout the IDN network.

Most encouraging has been the interest by other organizations who wish to use the directory to reference their data sets - providing their own data citation and access information. These organizations can participate as distributed nodes, use the JAVA-based MD8 client software for input, or simply participate as an individual by using the GCMD's authoring tools. The inner workings of the distributed system will be presented, along with the use of the JAVA-based MD8 client software.

The Directory Interchange Format (DIF) describes the content of the data sets and will be compliant with the new ISO 19115 standard for metadata. The standard for exchange of content among nodes is the Extensible Markup Language (XML).

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