5
User guide
Organization
Terms
The TGDT contains four types of terms.
¶ Preferred terms are those words and phrases which are to be used in indexing or
cataloging. Preferred terms normally appear in bold type: for example, sheetfed scanners
or dashed rules.
¶ Non-preferred terms (also known as lead-in terms) are words and phrases for which
preferred terms are to be substituted in actual use; these are intended as an aid to users in
finding preferred terms, and appear in regular type.
¶ Guide terms are descriptive labels used to structure the thesaurus, bringing together
terms that are subordinate to a common concept for which no acceptable term exists; like
non-preferred terms, they are not meant to be used as indexing terms. They are found
only in the systematic listing, where they appear in italics within angle brackets: for ex-
ample,
¶ Identifiers are proper nouns that designate individual, unique persons, languages,
works, and so on. Because the set of identifiers is unbounded, only selected identifiers are
listed in the thesaurus; these appear in italics within square brackets: for example, [Photo
shop (software)] or [American Sign Language]. Furthermore, identifiers are not considered
part of the TGDT proper; rather, they are ancillary terms listed only for the convenience
of users. Appendix B describes the five classes of identifiers listed in the TGDT.
Terms that might otherwise be ambiguous contain a parenthetical qualifier: for exam-
ple, printers (people) and printers (computer peripherals) are distinguished in this
manner. Lead-in terms and identifiers also contain qualifiers as needed.
Facets
The terms in TGDT are organized in nine facets, described below. As in other faceted
thesauri and classification schemes, each facet is “a homogeneous class of terms whose
members share characteristics that distinguish them from members of other classes”
(Petersen, 1994b, p. 7). These classes are, for the most part, distinguished by linguistic
factors rather than simple relatedness. For example, terms in the TGDT that relate to
printed books are found in several facets: book design and book trade in the Activities