Using Controlled Vocabulary

When you search in an online database or in the library catalog, you are usually given the option of searching by Keyword or by Subject.

• Keyword searching is the broadest kind of searching you can do. Keyword searching searches for the term(s) you entered anywhere within a record (author field, title field, subject field, abstract, full-text, if available, etc.) This is the broadest and most general kind of searching you can do.
• Subject searching searches only the subject heading (also called a descriptor in some databases). Creators of databases will often use a standardized set of vocabulary (often called a controlled vocabulary or thesaurus) to describe the contents of a record, a journal article, book, book chapter, etc. A controlled vocabulary is an established list of standardized terminology for use in indexing and retrieval of information. Using the same terminology throughout a database creates consistency and precision and helps you find relevant information no matter what terminology the author may have used.

Most databases (but not the Internet) are built with standard or controlled vocabulary, usually called subject headings in bibliographic databases. To find out what the subject headings are, you can, in most cases, simply do a keyword search, retrieve a record that looks like it is appropriate to your topic and then check the subject headings for that record.

One of the most commonly used controlled vocabulary is the Library of Congress Subject Headings (LCSH). It is used primarily in databases which list books, such as the Library Catalog. You will find the controlled vocabulary terms in the subject field of the record.

The terms listed in the SUBJECT field are the controlled vocabulary terms from the LCSH. In the library catalog, click on the subject heading to locate more records with the same subject.

Periodical Indexes or databases may use the LCSH, but most of them have their own controlled vocabulary. Some databases such as ERIC, PsycInfo, Sociological Abstracts, Social Services Abstracts, Linguistics and Language Behavior Abstracts and MEDLINE, even develop very complex controlled vocabulary or thesauri. In order to search these databases effectively, you need to look at the controlled vocabulary for each database.

Below is an example of the controlled vocabulary for ERIC, an education database.

The DESCRIPTORS (DE) are the subject terms which describe the content of this article. In the online database, click on a descriptor to locate more records with the same subject.

Search the Thesaurus

Some databases will include an online version of their controlled vocabulary, usually called a thesaurus, you can search to find out if a term is a controlled vocabulary item or to find broader, narrower or terms related to your topic. Below is an example of a thesaurus search in the ERIC database.

Not all databases will provide you with broader subject headings or related subject headings the way this database does. But looking for the subject headings in a record is an excellent way of finding more information on the same topic.

Last updated: 09/09/2004