THESAURUSA. ROSELINE

MLIS 2ND YEARPONDICHERRY UNIVERSITY

INTRODUCTION The word `thesaurus' comes from

Greek term `thesauros' meaning a storehouse or treasury of words.

Quotes its use in 1736 as a treasury or store house of knowledge.

Thesaurus was first conceived by Peter Mark Roget, who brought out in 1825 his thesaurus of “English words and Phrases”.

DEFINITION’S A compilation of words and phrases

showing synonyms and hierarchical and other relationships and dependencies, the function of which is to provide a standardized vocabulary for information storage and retrieval systems. (Rowely,1992)

A thesaurus is a book of words that shows relationship among the words it contains. (Allen Kent)

Functions of a Thesaurus To provide standard vocabulary for a given subject

area by exercising control on the vocabulary of terms used in an indexing language.

To provide an aid to indexers in selecting term(s) for describing the subject matter of documents.

To help users to formulate their queries precisely.' To provide display of-relationships between terms to

facilitate the conduct of a comprehensive search systematically.

To provide a system of references between terms which will ensure that only one term from a set of synonyms is to be used both for indexing and searching.

There are three major part of a thesaurus

1. Descriptors2. Non descriptors3. Relationship between terms i. Hierarchical relationship ii. Non-Hierarchical relationship

Descriptors

The terms that have been defined for �use by the thesaurus.

For use in indexes. Descriptor should be nouns, either

single nouns, noun phrases or nouns with qualifiers indicated in parentheses

Descriptors

Motor vehicles MT 6.60 Equipment and facilities UF Automobiles UF CarsUF TrucksBT Vehicles RT Road Engineering RT Road Transport

Non-descriptor

A non-descriptor, also called �forbidden term, is a term designating a concept very close to that represented by a descriptor.

It contains a reference to the �corresponding descriptor as the only relationship

Non-descriptor Automobiles USE Motor vehicles Cars USE Motor vehicles Trucks USE Motor vehicles

Hierarchical Relationship It shows the interrelationship between

concepts in a hierarchy. It refers to super ordinate and

subordinate relationship for a concept. This relationship may be of three types: i. Genus-Species (Generic) relationship ii. Hierarchical Whole-Part relationship iii. Instance Relationship

Genus - Species (Generic) Relationship

It links genus and species and represents the basis of scientific, taxonomic system.

For Example: Capital Markets BT Financial Markets Financial Markets NT Capital Markets

Hierarchical Whole-Part relationship

It means that the name of a part implies the name of its whole in any context.

For Example: Science NT Physical Chemistry

Physical Chemistry BT Science

Instance Relationship occurs in a particular instance, which

links proper name with common noun.

For Example: Mountain NT Himalayas Himalayas BT Mountain Regions

Non-hierarchical Relationship

Two terms are related other than hierarchical, the relationship may be called non-hierarchical relationship. Two types are:

i. Equivalence (or preferential) relationship ii. Associative (or affinitive) relationship

Equivalence (or Preferential) Relationship

It refers to the preferred terms and distinguishes such terms from the non-preferred terms.

When terms are regarded as similar or almost the same in meaning, they can be combined with the same concept. Synonyms, near-synonyms, and quasi-synonyms come under this category.

The symbols used to represent these relationships in a thesaurus are USE and OF (Used For).

Cont.…

For Examples:1. Popular names and scientific names E.g. Onion/ Allium cepa2. Variant spelling E.g. Pray/ Prey3. Terms from different cultures E.g. Flat/ apartment4. Abbreviations and full names E.g. WHO/ World Health Organization

Associative (or Affinitive)

Relationship

This relationship is employed to cover other relationship between terms that are related but are neither consistently hierarchical nor equivalent. They are indicated by the code RT (Related Terms).

Two types of associative relationship are: i. Same Category e.g. Aero plane - Helicopter ii. Different category e.g. Operating system - Software

STRUCTURE OF THESAURUS DESCRIPTOR (With scope note whenever needed) Synonyms and quasi-synonyms (displaying equivalence relationship and denoted by the relationship indicator USE/UF (Use For) Broader Terms (displaying hierarchical - subordinate relationship and denoted by BT) Narrower Terms (displaying hierarchical - subordinates relationship and denoted by NT) Related Terms (displaying associate relationship and denoted by RT) Top Term (displaying hierarchical - subordinates relationship and denoted by TT . Top term or TT is not repeated when all the descriptors belong to the same broad class).

Steps in thesaurus1. Need Analysis: The thesaurus need analysis should be done first, whether it is really needed or not. There may be existing thesaurus on similar subjects.2. Gathering of Terms: The terms are collected using two principles - Principle of Literary warrant and Principle of User Warrant. In the former the logic is that a term justifies its inclusion if it is used in literature of the subject. The method is to go through abstracting sources, reference sources, periodical articles, etc. In the later case, users/ subject specialists may be consulted to gather the terms.

Cont.….3. Organization of Terms To be organized into major categories and into hierarchies within the categories. Useful inter-hierarchical relationships should also be delineated.4. Organization into Hierarchies Once the categories are identified, the next stage is to organize each term into hierarchies.Indexing Languages –Part I: Concepts and Types, Subject Headings Lists and Thesauri

Cont.…..5. Creation of Alphabetical Thesaurus The hierarchies are established, the classification is inserted to create alphabetical thesaurus. Each term becomes an entry and its hierarchical relationships are denoted by BT and NT. All the BT and NT terms should reciprocate. Similarly the non-hierarchical relationships are shown through use, used for and related terms (RTs).

Cont.…..6. Presentation of Thesaurus Each block of entries are arranged according to requirement. It may be alphabetical, systematic (to complement) or graphic.7. Admission and deletion of termsThe job of inclusion of terms along with all their relationships into the thesaurus, and their display in the chosen format. At this stage some terms may need to be added or deleted.8. Evaluation Once the thesaurus is compiled it needs to be evaluated to assess its retrieval effectiveness.

Cont.…..9. ReviewOnce the thesaurus has been compiled, it has to be reviewed by subject experts and modified as necessary

10. Maintenance a thesaurus is developed, it should be maintained properly. New terms need to be added or deleted as the case may be. This has to be done continuously.

Display of terms in a thesaurus

1. Alphabetical display: In this form of display all indexing terms, whether preferred or non-preferred, are organized in a alphabetical sequence. Each preferred term in the following order:i. Scope note or definitionii. UF references to non-preferred

equivalent terms

Cont.….

iii. TT references to top-termsiv. BT references to broader termsv. NT references to narrower termsvi. RT references to related terms.Non-preferred terms are accompanied only by references (e.g. USE) to the preferred terms.PREFERRED TERMSN Scope noteUF Use forBT Broader termNT Narrower termRT Related termNon-preferred termUse PREFERRED TERM

Cont.…MICROFORMSSN A miniature of replica of documentUF Micro copies BT Data media NT Micro transparencies Micro-opaques RT Microphotography

Systematic display

1. Categories or hierarchies of terms arranged according to their meanings and logical relationships, and

2. An alphabetical index that directs the user to the appropriate part of the systematic section.

Graphic Display

Graphic display shows the indexing terms and their relationship in the form of two dimensional figures, which are supplemented by alphabetical sections. There are two types1. Tree Structures and2. Arrowgraphs

Example of thesaurus NAL Agriculture Thesaurus (United States National

Agricultural Library, United States Department of Agriculture)

Evaluation Thesaurus (By M. scriven) Thesaurus of Psychological index Terms CAPA Clinicians’ Thesaurus (By E. Zukerman) ROGET'S Thesaurus

(http://humanities.uchicago.edu/forms_unrest /ROGET.html)

Thesaurus of Engineering and Scientific Terms (TEST) ERIC Thesaurus for Education Thesaurus of American Psychological Association (APA) UNESCO Thesaurus, etc.

Criteria for evaluating a thesaurus

Davis and Rush propose the following criteria for evaluating thesaurus. Terminology: is it appropriate for the field, up-to-date

and accurate? Scope: is it too broad or too narrow to cover the field

adequately? Subdivisions: are there reasonable subdivisions? Definitions and notes: are enough included for clarity? References: are they adequate in both number and

form? Format: is it legible? Classification numbers: is the listing keyed to any

kind of classification scheme, if appropriate?

The major purposes of a thesaurus

 1. To provide a map of a given field of knowledge, which helps an indexer or a searcher to understand the structure of the field.2. To provide a standard vocabulary for a given subject field.3. To provide a system of references between terms which will ensure that only one term from a set of synonyms is used for indexing one concept.4. To provide a guide for users of the systems so that they choose the correct term for a subject search.5. The use of terms in a given subject field may be standardized.

CONCLUSION Thesauri is a vocabulary control in an indexing

language. It is a list of terms arranged in some meaningful

form and provides hierarchically and non-hierarchically.

It provides control over synonyms, it distinguishes homographs and it brings related terms.

Exert terminology control in choosing proper headings subject cataloguing and indexing.

Increases speed of information retrieval system. It helps for the user find out information on a

specific topic but also on related topics.

THANK YOU!