Having decided that you need to build your own thesaurus, the first stage in the process is to gather the vocabulary. There are several ways in which you can do this, and which method you choose may depend on the use to which the thesaurus will be put. Further on in this chapter we will look at the factors that may affect this decision. You do need to keep in mind the fact that the thesaurus will be used for indexing, object description, or document management of some sort, and not for making a theoretical study of the subject itself. You should therefore always consider whether individual terms are useful for the purpose of information retrieval, and whether they correspond to the material to be organized.

There are a number of potential sources that can be mined for terms. They fall into two groups: sources of actual terms and sources of document titles. Collecting document titles is an essential part of assembling vocabulary, but some additional work will be required to derive terms from the titles.

Existing vocabularies

The most obvious and most accessible source of terminology will be published vocabulary tools. These can be divided into two categories:

The first category includes such things as classification schemes, subject heading lists, keyword lists, taxonomies and other thesauri – in fact, all the kinds of tools we considered in Chapter 3. These have the advantage that the terms in the vocabulary will be intended for document (or object) description, so that they will be of the kind and form that are required for a thesaurus. Vocabularies may also give a sense of the structure of the subject. The disadvantage, particularly for technical subjects, is that the meaning of terms may not be provided.

The second group embraces general and subject specialist encyclopaedias, and subject-specific dictionaries, glossaries and word lists intended for use in subject work. These tools have the advantage that the terms are accompanied by definitions which may be necessary at the stage of analysing and organizing the vocabulary.