Section F Structure: basic relationships andclassificationAn intrinsic feature of a thesaurus is its ability to distinguish anddisplay the structural relationships between the terms it contains. In thissection, the different types of relationship are identified, defined andillustrated, with reference to the Standards ISO 2788 and BS 5723. Theassociated topic of the display of relationships is treated in Section H.There are two broad types of relationship in a thesaurus. The first is atthe micro level and concerns the semantic links between individualterms. The three basic relationships, equivalence, hierarchical, andassociative, are described in F1—3.The second type of relationship is at the macro level, and concerns therelationships of sets of equivalent terms, and categories of hierarchicaland associated terms, to one another and to the subject field as a whole.It is essential to study macro as well as micro level relationships if it isintended to produce a systematic display. It is also advisable, even ifsuch a display is not intended, because an understanding of the structureat both levels will improve the quality of decisions made at the microlevel concerning inter-term relationships. The two types of relationshiptend to be interactive.To determine inter-term groupings and the organization of these withinthe subject field, classificatory techniques are employed. These includeclassification in its broadest sense: ‘arranging in classes according to amethod’ and classification with more specific meanings in informationwork, such as systematic classification and automatic classification. Insystematic classification a sequence of classes is brought together andorganized by a coding system, or notation. Faceted classification,described in F4, is a species of systematic classification, that uses facetanalysis, a technique involving the allocation of concepts td theirfundamental categories, applicable not only in subject fieldorganization, but also in distinguishing different inter-termrelationships.Automatic classification, the use of statistical and linguistic techniquesfor the computer-aided generation of inter-term relationships, isdiscussed in F6.F1. The equivalence relationshipAs defined by the Standards ES 5723 and ISO 2788, this is ‘therelationship between preferred and non-preferred terms where two ormore terms are regarded, for indexing purposes, as referring to the34Structure: basic relationships and classification 35same concept’. In other words, they form an equivalence set. Thepreferred term is the one chosen to represent the concept inindexing, while the non-preferred term (or terms) is the one notselected. The non-preferred terms form an ‘entry vocabulary’directing the user from terms not selected to those which are. Thefollowing conventions are used to express the reciprocalrelationship:UF(use for)written as a prefix to the non-preferred termUSEwritten as a prefix to the preferred termExample:PERMITTIVITYUF Dielectric ConstantDielectric ConstantUSE PERMITTIVITYIn the alphabetical display of a printed thesaurus (see Hi), it is usual todistinguish typographically between the preferred and non-preferredterms.The equivalence relation includes true synonyms and quasi-synonyms.F1.1 SynonymsThe Standards define synonyms as ‘terms whose meanings can beregarded as the same in a wide range of contexts, so that they arevirtually interchangeable’. In general linguistics, synonyms are notcommon, but they do occur more frequently in scientific terminology.This is due to the proliferation of trade names and popular names andother variations depending on local usage and opinion or onetymological root. In all subject fields, not only scientific, there aremore synonyms in controlled language than in natural language,because the meanings of terms are intentionally limited in controlledlanguage.There are several types of synonym. Those listed below are typical oftrue synonyms likely to occur in thesaurus-building.o Popular names and scientific namesExamples:FLIP-FLOPS / BISTABLE MULTIVIBRATORSSPIDERS / ARACHNIDAMERCY KILLING / EUTHANASIAo Common nouns or scientific names, and trade namesExamples:AMODIAQUINE / CAMOQUINPOLYMETHYL METHACRYLATE / PERSPEX36 Thesaurus construction o Standard names and slang.Examples:HIGH FIDELITY EQUIPMENT I HI-FI EQUIPMENTSUPPLEMENTARY EARNINGS / PERKSo Variant spellings — including stem variants and irregular pluralsExamples:GIPSIES / GYPSIESMOSLEMS / MUSLIMSMOUSE / MICEFIBRE OPTICS / FIBER OPTICSHAEMODYNAMICS / HEMODYNAMICSThe last two are examples of differences beween standard English andNorth American spelling.o Terms of different linguistic originExamples:DOMICILIARY CARE / HOME CAREALIENS / FOREIGNERSGEOMAGNETISM / TERRESTRIAL MAGNETISMCAECITIS / TYPHLITISo Terms originating from different cultures sharing a common languageExamples:AERIALS / ANTENNAPOSTAL SERVICES / MAIL SERVICESRAILWAYS / RAILROADSPAVEMENTS / SIDEWALKSo Competing names for emerging conceptsExamples:NON-ACCIDENTALLY INJURED CHILDREN / BATFEREDCHILDRENDISTANCE LEARNING / HOME LEARNING AWARENESSGAMES / ICE BREAKERSOnce the pattern of usage clarifies, the preferred term may be changed.For example, LIFELONG EDUCATION is now usually preferred toCONTINUING EDUCATION, although both were popular at onetime.o Current or favoured term versus outdated or deprecated termExamples:DISHWASHERS / WASHING-UP MACHINESJOB CENTRES / EMPLOYMENT EXCHANGESCOMMUNITY HOMES / ORPHANAGESHOVERCRAFT / AIR CUSHION VEHICLES / GROUNDEFFECT VEHICLESStructure: basic relationships and classification 37o Abbreviations and full namesExamples:ECG / ELECTROCARDIOGRAPHYPPBS / PLANNING-PROGRAMMING-BUDGETING SYSTEMSINDOR / INTERNUCLEAR DOUBLE RESONANCEThe full form of the term is usually preferred in a general index, but in aspecial field, where the abbreviated form is the most familiar, theabbreviation should be preferred, except where the same abbreviationstands for two different terms likely to occur in the same thesaurus.Example:BBC / BRITISH BROADCASTING CORPORATIONBBC / BROWN BOVERI COMPANYSome acronyms are now so familiar that their original meaning has beenlost. LASER, for example, could be shown without its full form ‘Lightamplification by stimulated emission of radiation’ being given as anentry point.o The factored and unfactored forms of a compound termExamples:MILK HYGIENE / MILK and HYGIENEPRISONERS FAMILIES / PRISONERS and