Global Change Master Directory (GCMD) Keywords

An Overview - 6/3/2024

Valere Dixon (valerie.dixon@nasa.gov), NASA ESDIS

Way back in the 1990s…

… with the Landsat missions of the 70’s and 80’s fueling a growing demand for Earth science & observation data, NASA created the Global Change Master Directory (GCMD).

Around the same time, NASA became involved in the international Committee on Earth Observation Satellites (CEOS), and GCMD (by way of the International Directory Network (IDN)) became NASA’s main contribution to enabling international cooperation and collaboration of Earth Observation data.

A catalog for NASA’s Earth Science data, the GCMD grew alongside the Earth Observing System Data and Information System (EOSDIS), which was conceived to archive and disseminate Earth science data.

It took 20 years for the two projects to officially merge within the Earth Science Data and Information System (ESDIS) Project, though the technologies of the two projects had been growing increasingly co-dependent for years.

Through all the consolidation and renaming of tools and applications, the GCMD Keywords - a hierarchical controlled vocabulary that describes Earth science data, services, variables and more - remain.

GCMD’s Keywords remain essential to search and discovery and many core ESDIS services.

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https://www.earthdata.nasa.gov/eosdis

https://www.earthdata.nasa.gov/esdis

https://www.earthdata.nasa.gov/learn/find-data/idn/gcmd-keywords

https://ceos.org/

https://idn.ceos.org/index.html

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GCMD Today

GCMD Keywords are ever-evolving to suit the needs of NASA’s EOSDIS community. The following are current GCMD tools:

• The GCMD Keyword Viewer is a Graphical User Interface to navigate the GCMD Keyword hierarchies.
• The Keyword Management System (KMS) is a RESTful web service Application Programming Interface (API) for the GCMD Keywords, enabling access to the keywords as Simple Knowledge Organization System (SKOS) objects; there’s also a Static KMS Directory. See the User’s Guide for more information.
• The GCMD Keyword Forum, part of the Earthdata Forum, provides keyword users and metadata providers with an area for discussion of topics related to GCMD Keywords; to ask questions, submit keyword requests, discuss trade-offs, learn about Keyword releases, etc.

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https://wiki.earthdata.nasa.gov/display/ED/KMS+User%27s+Guide

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https://forum.earthdata.nasa.gov/app.php/tag/GCMD+Keywords

https://gcmd.earthdata.nasa.gov/KeywordViewer/

https://gcmd.earthdata.nasa.gov/kms/

https://gcmd.earthdata.nasa.gov/static/kms/

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GCMD Keyword Viewer

• While the Earth Science keyword category is most commonly known and referenced, GCMD Keywords house controlled vocabularies in many other categories too.
• The GCMD Keyword Viewer provides an easy to navigate interface that allows users to explore the various categories at length.

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https://gcmd.earthdata.nasa.gov/KeywordViewer/

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KMS RESTful API

• Allows navigation through the URL itself, enabling scripted access.

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https://gcmd.earthdata.nasa.gov/kms/

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KMS Static Directory

• Enables download of each keyword category as a static directory as an RDF, JSON, XML, or CSV file.

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https://gcmd.earthdata.nasa.gov/static/kms/

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KMS User’s Guide

• Walks you through how to use KMS API and Static Directory functionalities.
• Note: KMS API is primarily for programmatic use of GCMD’s Keywords.

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https://wiki.earthdata.nasa.gov/display/ED/KMS+User%27s+Guide

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GCMD Keyword Forum

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https://forum.earthdata.nasa.gov/app.php/tag/GCMD+Keywords

• Where the keyword community, from scientists to metadata curators to academics, can propose and discuss changes or additions to the GCMD Keywords.
• It is also where new Keyword releases are announced; these may occur as often as every two weeks, content pending.

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Keyword Uses in EOSDIS

A consistent vocabulary is crucial to enabling programmatic search & discovery and compatibility across tools and services.

• CMR and Earthdata Search rely on the controlled vocabularies of GCMD Keywords to work
• Keyword changes and additions come through the Forum, with broad potentially impactful changes put through an ESDIS Standards Coordination Office (ESCO) community review
• https://www.earthdata.nasa.gov/esdis/esco

GCMD Keywords has also contributed to Machine Learning (ML) tooling:

• GCMD Keyword Recommender (GKR), embedded within our Metadata Management Tool, suggests science keywords to metadata curators
• GKR is an ML-driven application that suggests science keywords to metadata curators based on the contents within a collection metadata record’s abstract and description fields
• Science Services Keywords have been recently introduced to GCMD, describing ML Training and Model data

Inter-agency collaboration:

• NOAA/USGS/NASA re-consolidation of Science Keywords
• Atmosphere and Oceans keywords reconciled and released in GCMD (v10.0 and v12.0, respectively)
• Curently on V18.6, as of June 2024
• Sun-Earth Interactions in progress
• CEOS partner agencies use various GCMD Keywords in their Earth Observation collection metadata…
• Numerous United States and International Agencies
• …which is housed in the ESDIS Common Metadata Repository (CMR) and made discoverable via the IDN at: https://search.earthdata.nasa.gov/search?portal=idn
• IDN is a portal of our Earthdata Search client, making NASA and CEOS Earth Science data (CMR’s contents) discoverable

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Earthdata Search

Search Client for CMR

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Search & Facet filters based off of CMR Tags and GCMD Keywords

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https://search.earthdata.nasa.gov/search

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Earthdata Search Portals

Search Portals allow projects to group topical subsets of data for search and discovery.

Same features as Earthdata Search.

https://search.earthdata.nasa.gov/search

https://search.earthdata.nasa.gov/search

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GCMD Keyword Recommender (GKR)

Within the Metadata Management Tool, the GKR suggests science keywords based on other content within the collection metadata; in this case, the test record’s abstract consisted of:

“Test file for water vapor and humidity in tropical jungles”

and the GKR suggested these Atmosphere keywords

https://mmt.uat.earthdata.nasa.gov/collection_drafts

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GCMD Tomorrow

Hierarchical keywords -> Semantic Ontology!

• But how…? When? With what resources?
• Earth Science Information Partners (ESIP) Semantic Web for Earth and Environmental Terminology (SWEET) is a start, maybe

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Knowledge Graph?

• We use GraphQL and GraphDB for metadata associations in CMR
• Currently lack the expertise and priority to look into how to use Graph for GCMD Keywords and/or associations, but there’s a path started

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Low-Hanging Fruit

• Create Unique ID’s for each Keyword
• And cite those in metadata so minor keyword updates don’t invalidate records

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Acronyms

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Thank you!

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Please reach out any time!

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Valerie Dixon

valerie.dixon@nasa.gov

NASA Earth Science Data & Information System

https://www.earthdata.nasa.gov/

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