The following notation is commonly used by thesauri to establish or define terminology:

UF=Use for
UF+=Use for in combination
NT=Narrower term
BT=Broader term
RT=Related term

For example, below is an authority used by AGROVOC to describe biodiversity:

BIODIVERSITY

UF biological diversity
UF ecosystem diversity
UF species diversity
UF+ biological diversity conservation
UF+ genetic diversity as resource
RT ecosystems
RT gene pools
RT germplasm
RT species

Naturally, the Clearing-House Mechanism can choose to accept or reject the above descriptor. Or, alternatively, it could modify it and create a new authority record (as in the CBD controlled vocabulary list):

BIOLOGICAL DIVERSITY

UF Biodiversity
UF Ecosystem diversity
UF Species diversity
UF Biological diversity conservation
UF Genetic diversity as resources
NT Agricultural biological diversity
NT Forest Biological diversity
NT Inland waters biological diversity
NT Marine and coastal biological diversity
NT Microbial resources
NT Marine and coastal biological diversity
NT Protected areas
RT Convention on Biological Diversity
RT Natural resources
RT : Ecosystems
RT : Gene pools
RT : Germplasm
RT Savanna ecosystem
RT Species
RT Sustainable use
RT Terrestrial ecosystems

In this example, information pertaining to biodiversity is established under biological diversity. A well designed database will lead a user to biological diversity even if the term used to search the database is a synonym, i.e., biodiversity. Note also that a term that has been established may lead the user to other terms that are narrower in scope or related in some manner. In the example above, agricultural biological diversity is an established, but narrower term. In the same vein, terrestrial ecosystems is an established but related term.

An established term can also give information on broader terms (BT). For example, ENVOC establishes the term environmental indicators as a broader term under environmental quality standards:

ENVIRONMENTAL QUALITY STANDARDS

· BT Environmental indicators

Note also that in ENVOC, the established term environmental quality standards would also appear under environmental indicators as a narrower term:

ENVIRONMENTAL INDICATORS

· NT Environmental quality standards

Sometimes it is necessary to search more than one term to find information needed. Assume for example, that users need information on Asian marine and coastal biological diversity. If a search is made under Asia, many results will be totally irrelevant. If a search is made under marine and coastal biological diversity, information about other regions will be included in the results. There is, however, a consistent, logical method to link terms to filter information found on web sites and databases. This method is called Boolean searching, and is commonly used by many popular Internet search engines.