Trent Library GlossarySubject Headings and "Controlled Vocabulary"Subject headings are used to help us locate the most relevant material because they represent the subject matter covered, usually using controlled vocabulary. Controlled vocabulary ensures that a term is used uniformly in every instance, so that if we find one item of use, a click on a subject heading will find other items with the same term. (That's important if we remember that computers search for letters rather than ideas.) It reduces the likelihood that we'll find irrelevant items in our results. Subject headings are controlled because they're applied using a set of rules. A word is always in the same form - for instance it may always be a plural noun ("parties" rather than "party"). We don't need to worry about different authors expressing something in a different way because the database applies the terms uniformly. TOPCAT uses the Library of Congress Subject Headings (LCSH) to identify the subject coverage of an item. This is a common system used in most academic libraries and by several databases. LCSH entries look like this: English literature--Women authors--History and criticism. Be careful when searching TOPCAT by subject, because in order to find anything you'll need to know exactly how that subject heading is entered. It's usually a better idea to search for keywords, and then click on subject headings applied to the items you find. Some items don't have subject headings, and a "subject" search won't find any of these. Some other databases also use controlled vocabulary. They may control the way an author's name is entered (as in Web of Science) or dates (as in Historical Abstracts), or subjects (as in PsycINFO). When this is the case, there may be a thesaurus or index where we can find the best term to use for our search. Some databases don't use any controlled vocabulary and whether we find something depends upon whether the author used the same term the same way in the title, abstract, or author-supplied keywords.
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