Vocabularies: Dictionaries, Ontologies, and More

In many professional communities, the terminology used to communicate is often discipline-specific. For example, consider the use of the word "altitude." Altitude refers to the height of something above a reference point (like ground level), such as an airplane in flight. Although altitude is a common term, if we were examining a set of blueprints for a building we probably would not think of using the word 'altitude' to describe the level of the rooftop. Most likely, we would use the word "height." Similarly, if we were in a boat looking downward into the water, we probably wouldn't use "altitude" or "height" to describe the position of the bottom; rather we would use the word "depth."

The three words-altitude, height, and depth-are all similar in that they represent measures of distance relative to specified levels; but they are all used differently. As well, they can be associated with different communities. In this simple example, those communities include aviation, architecture and oceanography. What's more, the same term might be used differently in a different community, as when oceanographers use "altitude" to mean the distance above the ocean floor (for example, when operating a Remotely Operated Vehicle (ROV).

Various kinds of controlled vocabulariesA managed list of terms. In the context of vocabularies, management typically includes careful selection of terms, maintenance of terms over time (i.e. addition, deprecation, modification), and presentation of the vocabulary in an accessible format. Related Guide exist, but all can help improve metadataData about data. Metadata provides a context for research findings, ideally in a machine-readable format. It enables discovery of data via an electronic interface, and correct use and attribution of findings. Related Guide by restricting and better defining the content of metadata entries.

Controlled Vocabulary Management

Regardless of the type of controlled vocabulary you implement, it is useful to understand the process of managing a controlled vocabulary. Of course, your management tasks can be avoided if you use the vocabularies managed by another organization- usually a good idea (see Choosing and Implementing a Controlled Vocabulary). A controlled vocabulary may not exist that meets a project's needs, and a group will then need to become a controlled vocabulary manager (see A Last Resort... Developing a Local Controlled Vocabulary). In either case, it is very useful to understand the essence of controlled vocabulary development. What follows is a very simplified synopsis of the controlled vocabulary development process.

Simplified Controlled Vocabulary Development and Management

1. Clearly define the need for a controlled vocabulary. Individuals or groups that manage controlled vocabularies must, first and foremost, meet the needs of the appropriate scientific and technical community.
2. Using community expertise, evaluate each candidate term. Is the term widely used? Does it have appropriate meaning to the community?
3. After a thorough review, format the controlled vocabulary. Different types of controlled vocabularies can be implemented using different formats.
4. Register the controlled vocabulary with an appropriate organization.
5. Use the controlled vocabulary in community projects. Solicit input from implementing organizations.
6. Incorporate user community input to improve future versions of the controlled vocabulary.

Throughout the management process, the controlled vocabulary may evolve. For example, if an organization begins with an authority fileA type of flat controlled vocabulary that consists of a list of labels and terms which can be used for establishing the acceptable content, for example a metadata element or database field. Related Guide, they can provide descriptions and etymology in future versions of the controlled vocabulary. This will enhance the authority file and evolve it into a dictionaryIn the context of metadata, a dictionary is a type of controlled flat vocabulary, which provides a list of metadata terms, definitions and additional information within a specific domain. Related Guide. Perhaps one of the implementing organizations will enrich the dictionary by submitting classifications, relationshipsConnections between metadata terms within a vocabulary. These relationships can connect terms by scope, provenance, or other well-defined criteria., and axioms to the managing organization for the dictionary. What started as an authority file has now become an ontologyA type of relational controlled vocabulary, which provides for categories, relationships, rules and axioms among metadata elements. Typically a hierarchy of classes and terms, an ontology is a machine-readable way of relating metadata terminology. Related Guide/dictionary combination. This is one important benefit of a controlled vocabulary- it can become a living resource, which is relatively easy to implement, update, enhance, and understand.