THE TOP-DOWN METHOD:

• Convene a group of subject experts to decide on the scope and broad categories of terms to be included.
• Use existing dictionaries and thesauri to decide on the terms and their relationships.
• Review and organize the preliminary term set: decide on preferred terms and make Use references from the variants and synonyms; and build hierarchical and associative relationships among the preferred terms.
• Produce a draft thesaurus, test index and revise.

THE BOTTOM-UP METHOD:

• Develop a group of subject experts to serve as advisors; work with them to determine the scope if it is not already set.
• If there is a set of representative already-indexed documents, use the index terms from this set as your preliminary term list.
• If not, index a set of representative documents using free language (i.e., no vocabulary control), and take this term set as your preliminary list.
• Build your thesaurus by reviewing and organizing these terms, using a variety of resources as aids, as in the top-down method.
• Refer to your subject experts on terms whose meaning or usage is unclear, and for advice on which variant or synonym to prefer (or on whether two terms really are synonyms in the field).
• Produce a draft thesaurus, test index, and revise.

MAINTAINING YOUR THESAURUS

A thesaurus is never "finished," unless it is no longer being used for indexing or its database is no longer being updated. Plan for maintenance before you even begin developing your thesaurus. A thesaurus which is not well-maintained quickly becomes a liability rather than an asset.

The above information was written by Jessica Milstead specifically for use on the ASI Web site. Copyright 1996, Jessica Milstead.

FOR MORE INFORMATION...

• American National Standard Guidelines for the Construction, Format, and Management of Monolingual Thesauri. Bethesda, MD: NISO Press, 1994. (ANSI/NISO Z39.19-1993, ISSN 10415653, ISBN: 1880124041).
• Aitchison, Jean, David Bawden, and Alan Gilchrist. Thesaurus Construction and Use: A Practical Manual. 3rd ed. Chicago/London: Fitzroy Dearborn, 2000. (ISBN 1579582737).
• Craven, T. Introductory tutorial on thesaurus construction. London, Ontario, Canada: University of Western Ontario, Graduate School of Library and Information Science. Step by step guidance on constructing a thesaurus, including collecting terms, deciding on the forms of terms, and choosing the appropriate relationships with which to link terms.

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