Organising content with controlled vocabularies

Why use controlled vocabularies?

Controlled vocabularies organise information and make it possible to catalogue, curate, retrieve and aggregate information across the European institutions. They make the European institutions’ information systems more interoperable and improve information retrieval, including search, for all stakeholders.

When a vocabulary is ‘controlled’, this indicates that it is created and managed by a community of experts (not crowdsourced) and that it evolves in a controlled manner based on a set of guidelines. A controlled vocabulary is a kind of common language that is understandable for humans and machines, allowing to describe ‘things’ like web content, persons, events, etc., and how they relate to one another.

Types of controlled vocabularies

Various types of controlled vocabularies are used in the European institutions. Depending on their features, these vocabularies are called taxonomies, thesauri, lists of terms or named authority tables. You will also see them being referred to as corporate vocabularies, corporate taxonomies, or local taxonomies.

Taxonomies and thesauri

A taxonomy is a type of controlled vocabulary that is based on unambiguous concepts, not just words. It gathers synonyms, acronyms, and variant spellings to ensure that content is not miscategorized because different users apply different terms for the same concept (e.g., cars instead of automobiles). A search restricted to a taxonomy retrieves concepts, not just matching words (e.g., searching for monitors will return content about display monitors for computers, not content using the verb “monitors/observes”). A thesaurus is a type of taxonomy with more elaborate relationships between concepts.

Vocabularies management

The Publications Office manages controlled vocabularies as a centralised service. Their website has a dedicated section where you can review the different types of controlled vocabularies used across the European institutions. It publishes vocabularies - in all the official EU languages - with a unique online identifier, so that machines can reference and ‘understand’ them; making it possible to use one set of vocabularies to describe similar things across multiple sites and languages.