Thesaurus (Relational Vocabulary)

Definition of a Thesaurus

In the context of metadataData about data. Metadata provides a context for research findings, ideally in a machine-readable format. It enables discovery of data via an electronic interface, and correct use and attribution of findings. Related Guide, a type of relational controlled vocabularyA managed list of terms. In the context of vocabularies, management typically includes careful selection of terms, maintenance of terms over time (i.e. addition, deprecation, modification), and presentation of the vocabulary in an accessible format. Related Guide which provides a list of metadata terms, with specific relationshipsConnections between metadata terms within a vocabulary. These relationships can connect terms by scope, provenance, or other well-defined criteria. between the terms.

Discussion

According to the Guidelines for the Construction, Format and Management of Monolingual Thesauri (ANSI/NISO Z39.19 - 2003), "A thesaurus is a controlled vocabulary arranged in a known order and structured so that equivalence, homographic, hierarchical, and associative relationships among valuesMetadata values are the content connected to metadata labels in a metadata element. For example, if the metadata label is "date", the metadata value could be "May 13, 2007". Related Guide are displayed clearly and identified by standardized relationship indicators that are employed reciprocally. The primary purposes of a thesaurus are (a) to facilitate retrieval of documents and (b) to achieve consistency in the indexing of written or otherwise recorded documents and other items, mainly for postcoordinate information storage and retrieval systems."

Four principal purposes are served by a thesaurus:

1. Translation. To provide a means for translating the natural language of authors, indexers, and users into a controlled vocabulary used for indexing and retrieval.
2. Consistency. To promote consistency in the assignment of index values.
3. Indication of Relationships. To indicate semantic relationships among values.
4. Retrieval. To serve as a searching aid in retrieval of documents.

There are a variety of relationships, which are described in ANSI/NISO Z39.19 – 2003, that can be used to relate terms in a thesaurus. A brief explanation of these can be found below, and on page 12 of the Standard.

* Abbreviation, or Thesaurus Code

Select Abstract Examples

	USE = Equivalent You might use the terminology "ConductivityTemperatureDepth" in your controlled vocabulary for data type. However, the scientific vernacular for this type of data is "CTDConductivity - Temperature - Depth ". In this scenario, CTD would not appear in your vocabulary, even though many scientists' first instinct would be to search for CTD. The thesaurus could enable discoveryUse of metadata values or vocabularies to find metadata or data sets. Related Guide by either CTD or ConductivityTemperatureDepth.
	BT = Broader Term You might also use the terminology "OverTheSideSample" in your controlled vocabulary for data type. However, CTD samples are a type of over the side sampling. In this case, you could relate these two values in your vocabulary as the same variety of event. In this scenario, you could construct a query of over the side samples, and your search results would include both the more generic OverTheSideSample and ConductivityTemperatureDepth.
	RT = Related To A water temperature reading would be included both in the ConductivityTemperatureDepth data, and in Meteorological data. However, while a relationship between ConductivityTemperatureDepth and Meteorological exists, it cannot be characterized as scope, or equivalence.

Example - Alexandria Digital Library Thesaurus
(Selected sections of the complete thesaurus)

Alphabetical Representation

beaches
SN: The gently sloping shore that is washed by waves, usually composed of sand and pebbles. [USGSUnited States Geological Survey Circ 1048]
UF: sandy areas
strands
BT: physiographic features
RT: coastal zones
dunes

educational facilities
UF: academies
agricultural schools
campuses
colleges
military schools
schools
seminaries
training centers
universities
BT: institutional sites
RT: library buildings
research facilities

faults
SN: A fracture in the Earth's crust accompanied by a displacement of one side of the fracture with respect to the other. [UGSG Circ 1048]
BT: tectonic features
NT: fault zones
fracture zones
rift zones
RT: earthquake features

harbours
USE: harbors

oceans
SN: One of the major divisions of the vast expanse of salt water covering part of the earth. [NIMA]
BT: seas
NT: ocean currents
ocean regions

Comma Delimited Representation

"beaches","Used for","sandy areas"
"beaches","Used for","strands"
"beaches","Related Terms","coastal zones"
"beaches","Related Terms","dunes"
"beaches","Scope Note","The gently sloping shore that is washed by waves, usually composed of sand and pebbles. [USGS Circ 1048]"
"beaches","Broader Terms","physiographic features"
"beacons","Use","reference locations"
"educational facilities","Used for","academies"
"educational facilities","Used for","agricultural schools"
"educational facilities","Used for","campuses"
"educational facilities","Used for","colleges"
"educational facilities","Used for","military schools"
"educational facilities","Used for","schools"
"educational facilities","Used for","seminaries"
"educational facilities","Used for","training centers"
"educational facilities","Used for","universities"
"educational facilities","Related Terms","library buildings"
"educational facilities","Related Terms","research facilities"
"educational facilities","Broader Terms","institutional sites"
"faults","Narrower Terms","fault zones"
"faults","Narrower Terms","fracture zones"
"faults","Narrower Terms","rift zones"
"faults","Related Terms","earthquake features"
"faults","Scope Note","A fracture in the Earth's crust accompanied by a displacement of one side of the fracture with respect to the other. [UGSG Circ 1048]"
"faults","Broader Terms","tectonic features"
"harbours","Use","harbors"
"oceans","Narrower Terms","ocean currents"
"oceans","Narrower Terms","ocean regions"
"oceans","Scope Note","One of the major divisions of the vast expanse of salt water covering part of the earth. [NIMA]"
"oceans","Broader Terms","seas"

ADL Feature Type Thesaurus, Top Term Report, 10/03/01

hydrographic features
. aquifers
. bays
. . fjords
. channels
. deltas
. drainage basins
. estuaries
. floodplains
. gulfs
. guts
. ice masses
. . glacier features
. lakes
. seas
. . oceans
. . . ocean currents
. . . ocean regions
. streams
. . rivers
. . . bends (river)
. . . rapids
. . . waterfalls
. . springs (hydrographic)
. thermal features

regions
. biogeographic regions
. . barren lands
. . deserts
. . forests
. . . petrified forests
. . . rain forests
. . . woods
. . grasslands
. . habitats
. . jungles
. . oases
. . shrublands
. . snow regions
. . tundras
. . wetlands
. cadastral areas
. climatic regions
. coastal zones
. economic regions
. firebreaks
. land regions
. . continents
. . islands
. . . archipelagos
. . subcontinents
. map regions
. . chart regions
. . map quadrangle regions
. . UTM zones
. research areas
. . ecological research sites
. . paleontological sites

In each of the three representations of this thesaurus, the standard relationships are used to connect various values. Notice the content (values and relations) are the same in each of the representations - they are simply presented in a different format.

Additional Information

USGS Thesaurus, along with FAQ