Documenting Keywords

Keywords are words or phrases that describe the metadata resource. They facilitate search, indexing and discovery of metadata, and are the largest single component of many metadata collections, regardless of the dialect. Keywords usually come from shared vocabularies in order to encourage consistency across metadata collections. Keywords can support text searches as well as facet searches.

ECHO

<ScienceKeyword>
    <CategoryKeyword>EARTH SCIENCE</CategoryKeyword>
    <TopicKeyword>ATMOSPHERE</TopicKeyword>
    <TermKeyword>ATMOSPHERIC CHEMISTRY</TermKeyword>
    <VariableLevel1Keyword>
        <Value>OXYGEN COMPOUNDS</Value>
        <VariableLevel2Keyword>
            <Value>OZONE</Value>
            <VariableLevel3Keyword>Keyword#3</VariableLevel3Keyword>
        </VariableLevel2Keyword>
    </VariableLevel1Keyword>
</ScienceKeyword>

DIF

<Parameters>
   <Category>EARTH SCIENCE</Category>
   <Topic>ATMOSPHERE</Topic>
   <Term>ATMOSPHERIC CHEMISTRY</Term>
   <Variable_Level_1>OXYGEN COMPOUNDS</Variable_Level_1>
   <Variable_Level_2>OZONE</Variable_Level_2>
   <Variable_Level_3>Keyword#3</Variable_Level_3>
   <Detailed_Variable>Uncontrolled Keyword</Detailed_Variable>
</Parameters>

SERF

<Parameters>
   <Category>EARTH SCIENCE</Category>
   <Topic>ATMOSPHERE</Topic>
   <Term>ATMOSPHERIC CHEMISTRY</Term>
   <Variable_Level_1>OXYGEN COMPOUNDS</Variable_Level_1>
   <Variable_Level_2>OZONE</Variable_Level_2>
   <Variable_Level_3>Keyword#3</Variable_Level_3>
   <Detailed_Variable>Uncontrolled Keyword</Detailed_Variable>
</Parameters>

FGDC

<keywords>
    <theme>
        <themekt> NASA/GCMD Earth Science Keywords </themekt>
        <themekey>EARTH SCIENCE > ATMOSPHERE > CLOUDS > CLOUD DYNAMICS > MOISTURE FLUX > DOWNWARD MOISTURE FLUX</themekey>
    </theme>
</keywords>

ISO

The MD_Keyword object in ISO 19115-1.

<mri:descriptiveKeywords>
  <mri:MD_Keywords>
     <mri:keyword/>         // Keyword
     <mri:type/>            // Type of Keyword (Theme, Instrument, Place etc)
     <mri:thesaurusName/>   // Reference to the controlled vocabulary keyword source (GCMD)
     <mri:keywordClass/>    // User-defined categorization of groups of keywords
  </mri:MD_Keywords>
</mri:descriptiveKeywords>

GCMD Vocabularies

NASA GCMD keyword vocabularies ensure that metadata is described in a consistent manner. There are seven sets of controlled keywords in the GCMD directory: (1) Earth Science, (2) Data Services, (3) Data Centers, (4) Locations, (5) Instrument/Sensors, (6) Platforms/Sources, and (7) Projects.

GCMD Keywords are organized into hierarchical groups ranging from general Category Keywords to very specific Variable Level Keywords. The GCMD keywords include the following hierarchy levels; Category > Topic > Term > Variable Level 1 > Variable Level 2 > Variable Level 3 > Detailed Variable. Earth Science Keywords, also know as 'Theme' Keywords are highly recommended by most metadata dialects.

EARTH SCIENCE > ATMOSPHERE > CLOUDS > CLOUD DYNAMICS > MOISTURE FLUX > DOWNWARD MOISTURE FLUX

Keyword Type Categories

As noted above GCMD includes 7 Keyword Set Categories. ISO 19115-1 includes 15 Keyword Type Categories. The table below provides a reference list and mapping of GCMD and ISO Keyword Types.

ISO Keyword Types	GCMD Keyword Sets
discipline
place	Locations
statum
temporal
theme	Earth Science
dataCentre	Data Centers
featureType
instrument	Instrument/Sensors
platform	Platforms/Sources
process
project	Projects
service	Data Services
product
subTopicCategory
taxon

Keyword

Keywords are used by many metadata dialects in order to enable discipline specific descriptions of various kinds and discovery using those descriptions. Keywords usually come from shared vocabularies in order to encourage consistency across metadata collections. Keywords can support text searches as well as facet searches.

Concept	Description	Dialect (Fit) Paths
Keyword Type	Methods used to group similar keywords	BDP /bdp:metadata/bdp:idinfo/bdp:keywords/bdp:theme/bdp:themekt CSDGM /csdgm:metadata/csdgm:idinfo/csdgm:keywords/csdgm:theme/csdgm:themekt EML /eml:eml/*/keywordSet/keyword/@keywordType ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:type/gmd:MD_KeywordTypeCode ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords/mri:type/mri:MD_KeywordTypeCode Mercury /mercury:metadata/mercury:idinfo/mercury:keywords/mercury:theme/mercury:themekt OGC-SOS /sos:Capabilities/ows:ServiceIdentification/ows:Keywords/ows:Type
Keyword Vocabulary	If you are following a guideline or using a shared vocabulary for the words/phrases in your "keywords" attribute, put the name of that guideline here. Note: DIF, ECHO and ECS require that theme keywords come from the Global Change Master Directory list.	ADIwg /adiwg:project/adiwg:idinfo/adiwg:keywords/adiwg:theme/adiwg:themekt BDP /bdp:metadata/bdp:idinfo/bdp:keywords/bdp:theme/bdp:themekt CSDGM /csdgm:metadata/csdgm:idinfo/csdgm:keywords/csdgm:theme/csdgm:themekt DCITE /dcite:resource/dcite:subjects/dcite:subject/@subjectScheme EML /eml:eml/*/keywordSet/keywordThesaurus HCLS void:vocabulary HDF5.1 /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Attribute[@Name='keywords_vocabulary']/hdf5:Data/hdf5:DataFromFile ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:thesaurusName ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[normalize-space(mri:type/mri:MD_KeywordTypeCode)='theme']/mri:thesaurusName/cit:CI_Citation MODS //mods:mods/mods:subject/@authority Mercury /mercury:metadata/mercury:idinfo/mercury:keywords/mercury:theme/mercury:themekt OGC-SOS /sos:Capabilities/ows:ServiceIdentification/ows:Keywords/ows:Type='theme']/ows:Type/@codespace RDA-CISL /rda:dsOverview/rda:variable/@vocabulary THREDDS //thredds:dataset/thredds:keyword/@vocabulary THREDDS /thredds:catalog/thredds:dataset/thredds:geospatialCoverage/thredds:name/@thredds:vocabulary
Keyword Vocabulary Citation	Name of the formally registered thesaurus or a similar authoritative source of keywords.	ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:thesaurusName/gmd:CI_Citation ISO /*/gmd:identificationInfo/srv:SV_ServiceIdentification/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:thesaurusName/gmd:CI_Citation ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/mri:MD_DataIdentification/mri:descriptiveKeywords/mri:MD_Keywords/mri:thesaurusName/cit:CI_Citation ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/srv:SV_ServiceIdentification/mri:descriptiveKeywords/mri:MD_Keywords/mri:thesaurusName/cit:CI_Citation
Keyword Ontology Citation	Reference that binds the keyword class to a formal conceptualization of a knowledge domain for use in semantic processing.	ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/mri:MD_DataIdentification/mri:descriptiveKeywords/mri:MD_Keywords/mri:keywordClass/mri:MD_KeywordClass/mri:ontology/cit:CI_Citation ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/srv:SV_ServiceIdentification/mri:descriptiveKeywords/mri:MD_Keywords/mri:keywordClass/mri:MD_KeywordClass/mri:ontology/cit:CI_Citation
Keyword	A word or phrase that describes some aspect of a resource. Can be one of several types.	ADIwg /adiwg:project/adiwg:idinfo/adiwg:keywords/adiwg:theme/adiwg:themekey ADIwg /adiwg:project/adiwg:idinfo/adiwg:keywords/adiwg:place/adiwg:placekey BDP /bdp:metadata/bdp:idinfo/bdp:keywords/bdp:theme/bdp:themekey BDP /bdp:metadata/bdp:idinfo/bdp:keywords/bdp:place/bdp:placekey CSDGM /csdgm:metadata/csdgm:idinfo/csdgm:keywords/csdgm:theme/csdgm:themekey CSDGM /csdgm:metadata/csdgm:idinfo/csdgm:keywords/csdgm:place/csdgm:placekey DCAT /dct:keyword DCITE /dcite:resource/dcite:subjects/dcite:subject DIF /*/dif:Keyword DIF /*/dif:AncillaryKeyword DIF /dif:DIF/dif:Location/dif:Location_Category DIF /dif:DIF/dif:Location/dif:Location_Type DIF /dif:DIF/dif:Location/dif:Location_Subregion1 DIF /dif:DIF/dif:Location/dif:Location_Subregion2 DIF /dif:DIF/dif:Location/dif:Location_Subregion3 DIF /dif:DIF/dif:Location/dif:Detailed_Location DIF /dif:DIF/dif:Sensor_Name/dif:Short_Name DIF /dif:DIF/dif:Sensor_Name/dif:Long_Name DIF /*/dif:Source_Name/dif:Short_Name DIF /*/dif:Source_Name/dif:Long_Name DIF /*/dif:Project/dif:Short_Name DIF /*/dif:Project/dif:Short_Name DIF-10 /*/dif:Science_Keywords/dif:Category DIF-10 /*/dif:Science_Keywords/dif:Topic DIF-10 /*/dif:Science_Keywords/dif:Term DIF-10 /*/dif:Science_Keywords/dif:Variable_Level_1 DIF-10 /*/dif:Science_Keywords/dif:Variable_Level_2 DIF-10 /*/dif:Science_Keywords/dif:Variable_Level_3 DIF-10 /*/dif:Science_Keywords/dif:Detailed_Variable DIF-10 /*/dif:Ancillary_Keyword DIF-10 /dif:DIF/dif:Location/dif:Location_Category DIF-10 /dif:DIF/dif:Location/dif:Location_Type DIF-10 /dif:DIF/dif:Location/dif:Location_Subregion1 DIF-10 /dif:DIF/dif:Location/dif:Location_Subregion2 DIF-10 /dif:DIF/dif:Location/dif:Location_Subregion3 DIF-10 /dif:DIF/dif:Location/dif:Detailed_Location DIF-10 /dif:DIF/dif:Platform/dif:Instrument/dif:Short_Name DIF-10 /dif:DIF/dif:Platform/dif:Instrument/dif:Long_Name DIF-10 /*/dif:Platform/dif:Short_Name DIF-10 /*/dif:Platform/dif:Long_Name DIF-10 /*/dif:Project/dif:Campaign Dryad /*/dcterms:subject ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword/echo:CategoryKeyword ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword/echo:TopicKeyword ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword/echo:TermKeyword ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword/echo:VariableLevel1Keyword/echo:Value ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword/echo:VariableLevel1Keyword/echo:VariableLevel2Keyword/echo:Value ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword/echo:VariableLevel1Keyword/echo:VariableLevel2Keyword/echo:VariableLevel3Keyword ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword/echo:DetailedVariableKeyword ECHO /*/echo:ScienceKeywords/echo:ScienceKeyword//* ECHO /*/echo:Spatial/echo:GranuleLocality/echo:LocalityValue ECHO /*/SpatialKeywords/Keyword ECHO /*/echo:Platforms/echo:Platform/echo:Instruments/echo:Instrument/echo:ShortName ECHO /*/echo:Platforms/echo:Platform/echo:Instruments/echo:Instrument/echo:LongName ECHO //echo:Platforms/echo:Platform/echo:ShortName ECHO //echo:Platforms/echo:Platform/echo:LongName ECHO /*/echo:Campaigns/echo:Campaign/echo:ShortName ECHO /*/echo:Campaigns/echo:Campaign/echo:LongName ECS (1) /*/ecs:DisciplineTopicParameters/ecs:DisciplineKeyword ECS (1) /*/ecs:DisciplineTopicParameters/ecs:TopicKeyword ECS (1) /*/ecs:DisciplineTopicParameters/ecs:TermKeyword ECS (1) /*/ecs:DisciplineTopicParameters/ecs:VariableKeyword ECS /*/ecs:Platform/ecs:PlatformShortName ECS /*/ecs:Platform/ecs:PlatformLongName EML /eml:eml/*/keywordSet/keyword HCLS dcat:keyword HDF5.1 (1) /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Attribute[@Name='keywords']/hdf5:Data/hdf5:DataFromFile HDF5.1 (1) /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Group[@Name='METADATA']/hdf5:Group[@Name='COLLECTIONMETADATA']/hdf5:Group[@Name='DisciplineTopicParameters']/hdf5:Group/hdf5:Attribute[@Name='ECSDisciplineKeyword']/hdf5:Data/hdf5:DataFromFile HDF5.1 (1) /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Group[@Name='METADATA']/hdf5:Group[@Name='COLLECTIONMETADATA']/hdf5:Group[@Name='DisciplineTopicParameters']/hdf5:Group/hdf5:Attribute[@Name='ECSTermKeyword']/hdf5:Data/hdf5:DataFromFile HDF5.1 (1) /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Group[@Name='METADATA']/hdf5:Group[@Name='COLLECTIONMETADATA']/hdf5:Group[@Name='DisciplineTopicParameters']/hdf5:Group/hdf5:Attribute[@Name='ECSTopicKeyword']/hdf5:Data/hdf5:DataFromFile HDF5.1 (1) /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Group[@Name='METADATA']/hdf5:Group[@Name='COLLECTIONMETADATA']/hdf5:Group[@Name='DisciplineTopicParameters']/hdf5:Group/hdf5:Attribute[@Name='ECSVariableKeyword']/hdf5:Data/hdf5:DataFromFile HDF5.1 (1) /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Group[@Name='METADATA']/hdf5:Group[@Name='COLLECTIONMETADATA']/hdf5:Group[@Name='DisciplineTopicParameters']/hdf5:Group/hdf5:Group[@Name='ECSParameter']/hdf5:Attribute[@Name='ECSParameterKeyword']/hdf5:Data/hdf5:DataFromFile HDF5.1 /hdf5:HDF5-File/hdf5:RootGroup/hdf5:Group[@Name='METADATA']/hdf5:Group[@Name='COLLECTIONMETADATA']/hdf5:Attribute[@Name='SpatialKeyword']/hdf5:Data/hdf5:DataFromFile ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:keyword ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords[normalize-space(gmd:type/gmd:MD_KeywordTypeCode)='place']/gmd:keyword//* ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords[normalize-space(gmd:type/gmd:MD_KeywordTypeCode)='instrument']/gmd:keyword//* ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords[normalize-space(gmd:type/gmd:MD_KeywordTypeCode)='platform']/gmd:keyword//* ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords[normalize-space(gmd:type/gmd:MD_KeywordTypeCode)='project']/gmd:keyword//* ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[normalize-space(mri:type/mri:MD_KeywordTypeCode)='theme']/mri:keyword//* ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[normalize-space(mri:type/mri:MD_KeywordTypeCode)='place']/mri:keyword//* ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicDescription/gex:geographicIdentifier/mcc:MD_Identifier/mcc:code//* ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[normalize-space(mri:type/mri:MD_KeywordTypeCode)='instrument']/mri:keyword//* ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[normalize-space(mri:type/mri:MD_KeywordTypeCode)='platform']/mri:keyword//* ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[normalize-space(mri:type/mri:MD_KeywordTypeCode)='project']/mri:keyword//* MODS //mods:mods/mods:subject/mods:topic MODS //mods:mods/mods:genre Mercury /mercury:metadata/mercury:idinfo/mercury:keywords/mercury:theme/mercury:themekey Mercury /mercury:metadata/mercury:mercury/mercury:Parameter_Description/mercury:Sensor Mercury /mercury:metadata/mercury:mercury/mercury:Parameter_Description/mercury:Source Mercury /mercury:metadata/mercury:mercury/mercury:Parameter_Description/mercury:Term Mercury /mercury:metadata/mercury:mercury/mercury:Parameter_Description/mercury:Topic Mercury /mercury:metadata/mercury:idinfo/mercury:keywords/mercury:place/mercury:placekey Mercury /mercury:metadata/mercury:mercury/mercury:Site_Information/mercury:Site Mercury /mercury:metadata/mercury:mercury/mercury:Keywords Mercury /mercury:metadata/mercury:mercury/mercury:Parameter_Description/mercury:Parameter Mercury /mercury:metadata/mercury:mercury/mercury:Navpath OGC-SOS (1) /sos:Capabilities/ows:ServiceIdentification/ows:Keywords[ows:Type='theme']/ows:Keyword OGC-SOS /sos:Capabilities/ows:ServiceIdentification/ows:Keywords[ows:Type='place']/ows:Keyword OGC-SOS /sos:Capabilities/ows:ServiceIdentification/ows:Keywords[ows:Type='instrument']/ows:Keyword OGC-SOS /sos:Capabilities/ows:ServiceIdentification/ows:Keywords[ows:Type='platform']/ows:Keyword Onedcx /onedcx:metadata/onedcx:simpleDc/dcterms:subject RDA-CISL /rda:dsOverview/rda:variable RDA-CISL /rda:dsOverview/rda:keyword SERF /serf:SERF/serf:Keyword SERF /serf:SERF/serf:Sensor_Name/serf:Short_Name SERF /serf:SERF/serf:Sensor_Name/serf:Long_Name SERF /serf:SERF/serf:Source_Name/serf:Short_Name SERF /serf:SERF/serf:Source_Name/serf:Long_Name SERF /serf:SERF/serf:Project/serf:Short_Name SERF /serf:SERF/serf:Project/serf:Long_Name THREDDS (1) //thredds:metadata/thredds:keyword THREDDS (1) //thredds:dataset/thredds:keyword THREDDS /thredds:catalog/thredds:dataset/thredds:geospatialCoverage/thredds:name UMM (1) /umm:UMM/umm:ScienceKeywords/umm:Category UMM (1) /umm:UMM/umm:ScienceKeywords/umm:Topic UMM (1) /umm:UMM/umm:ScienceKeywords/umm:Term UMM (1) /umm:UMM/umm:ScienceKeywords/umm:VariableLevel1/umm:Value UMM (1) /umm:UMM/umm:ScienceKeywords/umm:VariableLevel1/umm:VariableLevel2/umm:Value UMM (1) /umm:UMM/umm:ScienceKeywords/umm:VariableLevel1/umm:VariableLevel2/umm:VariableLevel3/umm:Value UMM (1) /umm:UMM/umm:ScienceKeywords/umm:DetailedVariable

xPath Note: The xPaths included in this table use several wildcards. // means any path, so //gmd:CI_ResponsibleParty indicates a gmd:CI_ResponsibleParty anywhere in an XML file. /*/ indicates a single level with several possible elements. This usually indicates one of several concrete realizations of an abstract object. For example /*/gmd:identificationInfo could be gmd:MD_Metadata/gmd:identificationInfo or gmi:MI_Metadata/gmd:identificationInfo and gmd:identificationInfo//*/gmd:descriptiveKeywords could be gmd:identificationInfo/gmd:MD_DataIdentification/gmd:descriptiveKeywords or gmd:identificationInfo/srv:SV_ServiceIdentification/gmd:descriptiveKeywords.

Metadata Implementation