PH 570: Introduction to Health Informatics

Controlled Vocabularies 

• Controlled vocabularies are standardized and organized arrangements of words and phrases and provide a consistent way to describe data. Metadata creators assign terms from vocabularies to improve information retrieval.
• Not all databases use controlled vocabulary. 
• They're not keywords. 

Common Types of Vocabularies

• Term Lists: A term lists, sometimes called a pick list, is the simplest type of controlled vocabularies. 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.
• Authority Files: The next level of complexity in controlled vocabularies is the authority file. Like term lists, authorities 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. Additionally, alternate and variant terms could be indexed in databases, allowing users to find the appropriate resources, even if they do not know the proper term. Authority files are commonly used to identify proper forms of names, such as in the Library of Congress Name Authority File.
• Taxonomies:  A hierarchical classification or categorization 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. In comparison to authority files, which have preferred terms and variant terms, a taxonomy also includes a hierarchy, designating both broader and narrower terms. 
• Thesauri: A thesaurus is a kind of dictionary represents all the concepts for a specific domain in a consistent manner and labels each concept with a preferred term. Like the previously described examples of controlled vocabularies, thesauri contain preferred terms, variant terms, and broader and narrower terms. Additional, the thesaurus also includes related terms, which may or may not be part of the same hierarchical structure of the term. 

For Example: 

• Medical Subject Headings (MeSH) is created by the National Library of Medicine for indexing journal articles and books in the life sciences.
• AGROVOC  Multilingual Agriculture Thesaurus is used in agriculture and food science, including controlled terms in nutrition, fisheries, forestry, environment etc.
• International Classification of Disease (ICD) is the international standard to identify diseases and health conditions for clinical  and research purposes. 
• NASA Thesaurus covers aerospace engineering, the natural space sciences (astronomy, astrophysics, planetary science), Earth sciences, and the biological sciences.
• National Agricultural Library Thesaurus is a list of terms in English and Spanish for research in agriculture.