4. Semantic Relationships used in Controlled Vocabularies

4.1 Semantic Linking | 4.2 Equivalency | 4.3 Hierarchy | 4.4 Associative

4.2 Equivalency (8.2)

When the same concept can be expressed by two or more terms, one of these is selected as the preferred term.

The relationship between preferred and non-preferred terms is an equivalence relationship in which each term is regarded as referring to the same concept. The preferred term in effect substitutes for other terms expressing equivalent or nearly equivalent concepts. A cross-reference to the preferred term (the “term”) should be made from any synonym or quasi-synonym that functions as an entry term for the user.

The equivalence relationship is expressed by the following conventions:

• U or USE, which leads from a non-preferred (entry) term to the preferred term, and
• UF or USED FOR, the reciprocal relationship, which leads from the preferred entry term to the non-preferred term(s).

Example 87: USE and UF relationships

Aves USE birds
birds UF Aves

outline USE shape
shape UF outline

These relationship indicators are the equivalents of see and x (see from), respectively, in many traditional subject heading lists.

The equivalence relationship covers five basic types:

a) synonyms
b) lexical variants
c) Near-synonyms
d) generic posting
e) cross reference to elements of compound terms

4.2.1 Synonyms (8.2.1)

Synonyms are terms whose meanings are regarded as the same or nearly the same in a wide range of contexts. True synonyms are rare in natural language. Although the terms are interchangeable in many circumstances, usage may vary as a result of such factors as level of formality, professional vs. lay context, or pejorative vs. neutral vs. complimentary connotation. The examples listed below are illustrative of the various classes of synonyms that may be encountered in practice. A slash is used to separate the synonyms, indicating that the preferred term has not been selected.

Example 88: Synonyms of different linguistic origin
cats / felines
freedom / liberty
sodium / natrium
sweat / perspiration

Example 89: Popular and scientific name synonyms
aspirin / acetylsalicylic acid
gulls / Laridae
salt / sodium chloride

Example 90: Generic and trade name synonyms
petroleum jelly / Vaseline
photocopies / Xeroxes
refrigerators / Frigidaires
tissues / Kleenex

Example 91: Variant names for emergent concepts
hovercraft / air cushion vehicles

Example 92: Current or favored terms replacing outdated or deprecated terms
poliomyelitis / infantile paralysis
developing countries / underdeveloped countries

Example 93: Slang or jargon synonyms
helicopters / whirlybirds
psychiatrists / shrinks

Example 94: Dialectical variants
elevators / lifts
subways / undergrounds

In these and other cases, preferred terms should be selected to serve the needs of the majority of users, bearing in mind the criteria enumerated in sections 6 and 7. For the sake of predictability, these criteria should be applied consistently throughout the controlled vocabulary. If, for example, American spelling is preferred to British spelling, or scientific names are preferred to popular names, this decision should be explained in the introduction to the controlled vocabulary and should be applied consistently in the formulation of terms.

4.2.2 Lexical Variants (8.2.2)

Lexical variants differ from synonyms in that synonyms are different terms for the same concept, while lexical variants are different word forms for the same expression. These forms may derive from spelling or grammatical variation or from abbreviated formats.

Example 95: Lexical variants (direct versus inverted order, orthographic variants, stem variants, and irregular plurals)
radar antennas / antennas, radar
Romania / Rumania / Roumania
ground water / ground-water / groundwater
online / on-line
pediatrics / paediatrics
mice / mouse

Example 96: Full name and abbreviation variants
International Federation for Documentation / FID
pi mesons / pions
polyvinyl chloride / PVC

4.2.3 Near-Synonyms (8.2.3)

Near-synonyms are terms whose meanings are generally regarded as different, but which are treated as equivalents for the purposes of a controlled vocabulary. The extent to which terms are treated as near-synonyms depends in large measure upon the domain covered by the controlled vocabulary and its size. Near-synonyms may include antonyms or represent points on a continuum.

Example 97: Near-synonyms
sea water / salt water [variant terms]
meteors / meteorites / meteoroids [points on a continuum]
smoothness / roughness [antonyms]

For each of these sets of near synonyms, a vocabulary developer might decide to designate one of the terms as the preferred term with the understanding that it will retrieve all content described by the other terms as well.

NOTE: Antonyms can also be treated as related terms, rather than equivalent terms. See section 4.4 Associative Relationships.

As a general rule, terms should be treated as near-synonyms only in subject areas that are peripheral to the domain of the controlled vocabulary. When concepts can be distinguished in the controlled vocabulary domain with sufficient precision to justify their representation as separate terms, they should be individually defined and retained. If two concepts cannot be consistently and reliably differentiated from each other, however, a term for one concept should be selected as the preferred term and a USE reference made from the other.

4.2.4 Generic Posting (8.2.4)

Generic posting is a technique in which the name of a class and the names of its members are treated as quasi-synonyms, with the broader class name functioning as the preferred term.

Example 98: Generic posting for class members
waxes UF plant waxes
plant waxes USE waxes

UF beds
UF chairs
UF desks
UF tables

beds USE furniture
chairs USE furniture
desks USE furniture
tables USE furniture

If employed, this technique should be limited to the peripheral areas of a subject field, or used when the number of documents on the members of a class does not warrant its being split into subclasses. This practice places limits on the specificity of the controlled vocabulary, and should be used with discretion. The narrower terms are useful entry terms.

4.2.5 Cross-references to Elements of Compound Terms (8.2.5)

A USE....AND reference may be made from a compound term to its components in cases where the term is split and both components must be used in indexing or searching.

Example 99: Cross references to compound term elements
coal mining USE coal AND mining
ferromagnetic films USE ferromagnetic materials AND films

USED FOR . . . AND . . . is a reference that may be used for the reciprocal of the reference from the compound term, as UF alone can suggest that one of the two components could be used alone in searching for the concept.

Example 100: Cross references from compound term elements
coal USED FOR coal AND mining
mining USED FOR coal AND mining

To be continued: | 4.3 Hierarchy | 4.4 Associative

| Table of Contents |
| 1. Why Vocabulary Control | 2. Principles | 3. Structures | 4. Semantic Relationships |
| 5. Displays | 6. When to use | 7. Examples of use | 8. About Z39.19 |
©NISO, 2005 http://www.niso.org/

Source: Based on ANSI/NISO Z39.19-2005 ISBN: 1-880124-65-3 
Guidelines for the Construction, Format, and Management of Monolingual Controlled Vocabularies