Controlled vocabularies

Controlled vocabularies are used by data creators and data managers to standardise information. They are used for indexing and annotating data and associated information (metadata) in database and data files. They facilitate searching for data in web portals. They also enable records to be interpreted by computers. This opens up data sets to a whole world of possibilities for automated data workflows, computer aided manipulation, distribution, interoperability, and long-term reuse.

How can I use controlled vocabularies in my research?

Use of keywords drawn from a thesaurus is one way to enable browse-based discovery and to enhance searching. They are used in subject indexing schemes, subject headings, thesauri, taxonomies and other knowledge organisation systems. Using standardised terms, units, and concepts from controlled vocabularies in your metadata and research outputs can help to make your research more accessible, easier to understand, and enable it to be discovered by different networks.

Types of controlled vocabularies

There are different types of controlled vocabularies from simple term lists to complex machine-readable ontologies. Read through the types below and learn how to find ones relevant to your research field.

Authority Files

Authority files provide a consistent list of terms to describe different kinds of resources, but also include cross-references from variant or alternate terms. Authority files often include other contextual or biographical information to assist users with disambiguation. Providing the preferred term, along with alternate versions provides more context for the metadata creator. Authority files are commonly used to identify proper forms of names.

Term Lists

A term list is the simplest type of controlled vocabulary. To create a term list, an agreed upon list of words and/or phrases is developed to identify a specific characteristic of a person, event, object, or other "thing". To use a term list, the user must select a term identified in the list. There are no synonyms or related terms identified; it is just a simple list of terms. Term lists are usually best when there are not a lot of terms needed, such as lists of file formats or object types.

Taxonomies

The term "taxonomy" is often used as a generic term for any kind of controlled vocabulary. A taxonomy is a hierarchical classification or categorisation system in which all the terms belong to a single hierarchical structure and have parent/child or broader/narrower relationships to other terms. Taxonomies allow for classification according to a pre-determined system. A taxonomy includes a hierarchy, designating both broader and narrower terms.

Thesauri

A thesaurus is a type of dictionary that represents all the concepts for a specific domain in a consistent manner and labels each concept with a preferred term. Thesauri contain preferred terms, variant terms, and broader and narrower terms. The thesaurus also includes related terms, which may or may not be part of the same hierarchical structure of the term.

Where can I find controlled vocabularies relevant to my research?

The NERC Vocabulary Server (NVS) contains a list of thesauri and vocabularies for different scientific fields, and you can search their vocabulary collection for terms useful to you.

See the following link for an example to find controlled terms for units containing the word milligrams https://vocab.nerc.ac.uk/search_nvs/P06/.