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The GCMD Earth science
keywords evolve as new metadata records are
added and existing records are modified to
meet the changing needs of the Earth science
community. These keywords were
first offered to the public on April 24, 1995
as Version 1.0.0. At that time,
they were organized in a hierarchy constructed
of TOPICs, TERMs, and VARIABLEs.
Changes at the TOPIC level (top level) required
a change in the key version number.
TERM changes were indicated through the second
digit, with VARIABLE level changes indicated
using the third digit of the version number.
A TOPIC change was made in early 2003 when
the new TOPIC, Climate Indicators, was added
as Version 4.2.2. A fourth change
was made in July 2004 when the TOPIC name,
Radiance/Imagery, was changed to Spectral/Engineering
to more accurately describe the data sets
behind the TOPIC. The new version
number thus became "GCMD Keywords,
Version 5.0.1". A TERM addition
was made in March 2005 when the TERM,
Paleoclimate Reconstructions, was added.
New TERMs were added in May 2005 (Sun-Earth
Interactions) and in December 2005 (Climate
Indicators). New variables were
added in 2006, bringing the version to "GCMD
Keywords, Version 5.3.8".
In April 2007, the hierarchy was expanded
to two additional levels. A new
TOPIC, Biological Classification, was added
and inspired the extension of the science
keyword taxonomy to five levels.
This added functionality arose from consultations
with Ocean Biogeographic Information System
(OBIS, http://www.iobis.org) representatives
and resulted in the implementation of the
OBIS taxonomic categories. The TERMs
and VARIABLEs under Biological Classification
were further extended based on the following
authoritative taxonomic sources: Integrated
Taxonomic Information system (ITIS) [2007]
http://www.itis.gov, Global Biodiversity Information
Facility (GBIF) [2007] http://www.gbif.org,
and Species 2000 [2007] http://www.sp2000.org/.
In addition, the Topic, Hydrosphere,
was clarified by adding the modifier, "terrestrial".
Thus, the first digit for the keyword set
will be "6" (Topic level changes)
and the number of digits was extended to five
to include Topic, Term, Variable1, Variable2,
Variable3, and Detailed Variables.
The "Detailed Variables" serve as
a critical component of the keyword taxonomy,
by providing a level to specify uncontrolled
keywords that the author chooses to include
in the hierarchy. Thus, the latest
iteration should now be cited at "GCMD
Keywords, Version 6.0.0.0.0".
For additional information see the GCMD Science Keyword Rules and the Procedures for Modification of the GCMD
Keywords. The expanded vocabulary content will be made public several months after the release of MD9.8 when mappings between keyword versions will be made available beginning with version 6.0.0.0.0.
We are
pleased with the increased interest and use
of the Global Change Master Directory's (GCMD)
Earth science keywords. At this time, we are
requesting that the following citation be
used by those individuals and groups using
the GCMD keywords.
Olsen, L.M., G. Major,
K. Shein, J. Scialdone, R. Vogel, S. Leicester,
H. Weir, S. Ritz, T. Stevens, M. Meaux, C.Solomon,
R. Bilodeau, M. Holland, T. Northcutt, R.
A. Restrepo, 2007 .
NASA/Global Change Master Directory (GCMD)
Earth Science Keywords. Version 6.0.0.0.0
Why hasn't the new version of the GCMD keywords been released?
We are planning to release the new vocabularies to the users within the coming months.
We did not include in our estimates the depth and breadth of the impact the changes and additions on those who currently maintain their metadata using the GCMD keywords outside of the directory itself. Therefore, it appeared to be prudent to build a well-structured keyword server to handle the mappings from the current version of the keywords to the new and extended sets. The keyword server is targeted to save valuable time in translations for everyone involved and is being built now.
DISCLAIMER: We are in the process of completing keyword revisions. Users should not integrate the current keywords into their systems until the revisions are complete. Thank you.
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