Controlled vocabularies 

Controlled vocabularies are meant to organise knowledge that is classifiable in nature. They can be approached from a broad perspective or a more purpose-specific context. This last option is the usual case for the controlled vocabularies found in the EU Vocabularies website. In the context of the semantic web, controlled vocabularies have a double purpose.

The first purpose involves harmonising concepts to improve technical, business, institutional and inter-institutional communication.

The second purpose has to do with knowledge management and metadata interchange, and is geared to a machine-readable environment, meant to improve dissemination/discovery, repurposing/reuse, and collection/merging of data across the open and globally connected digital environment of the semantic web.

There is a third purpose very specific to the EU institutions, which comes from the multilingual nature of the European Union itself. Translation requirements are easily met with the conceptual nature of controlled vocabularies.

Authority tables 

In order to harmonise and standardise the codes and the associated labels used in the Publications Office and on interinstitutional level in the context of the data exchange between the institutions involved in the legal decision-making process, multiple authority tables have been created.


A thesaurus is a controlled and structured vocabulary where concepts are represented by labels. In the context of the EU Vocabularies, a thesaurus is a multilingual equivalent of the previous basic definition, where the same concept in each of the supported languages is represented by a single preferred label. Potentially, one or several alternative labels can also be linked to each language version of a concept. Check the available thesauri.

ATTO tables 

ATTO is an internal application of the Publications Office for managing translations. The acronym comes from the French term ‘Atelier des Tables de Traductions de l’Office des publications’ (Workbench for translation tables of the Publications Office). Find out more about ATTO tables.


Alignments are common in database interoperability projects and tasks however, from the perspective of the semantic web we are referring to ontology alignments when a variable degree of correspondence can be established between concepts that belong to different controlled vocabularies. Read more on alignments.


A taxonomy is a set of controlled vocabulary terms organised into a hierarchical structure. Each term in a taxonomy is in one or more parent/child relationship to other terms in the taxonomy.