Controlled vocabularies

A controlled vocabulary is an agreed list of terms definitions used to provide a unique label to a concept. Controlled vocabularies are usually discipline related; their main aim is to facilitate sharing of data in the same community. For this reason, it is important that the community participate in the development of the vocabulary and agrees to its adoption for this to be useful.

In some cases vocabularies have been created in relation to a specific project, and then more widely adopted. As an example, since CMIP is an intercomparison project with modelling groups participating from across the world, it was essential to its success to define and use controlled vocabularies. CMIP6 controlled vocabularies cover many different aspects: experiments, variables, realms, models, sub-projects, frequency, resolution and grid labels. Their definition and labels for variables, frequency and realms are often adopted by other climate data producers.

Another example of controlled vocabulary is the CF conventions standard_name table. Anyone can contribute by proposing a definition for variables which are not yet covered.

Keywords

Controlled vocabularies also provide keywords to use when publishing data. Keywords are a powerful instrument when used properly. They can greatly increase the discoverability of a dataset, which is why it is one of the few highly recommended attributes in the ACDD conventions. Unfortunately, there is not yet an agreed controlled vocabulary to be used specifically for climate science. Lots of climate terms are however covered by the Global Change Master Directory Keywords, maintained by NASA. For practical advice on how to apply keywords, see Choosing keywords in the technical tips section of this book.

Research Vocabulary Australia

ARDC manage a controlled vocabulary service Research Vocabulary Australia (RVA), to list vocabularies used by the Australian research community. As well as making it easier to find controlled vocabularies, RVA also allows research organisation to contribute and publish new vocabularies.