Charlyn P. Salcedo Instructor Types of Indexing Languages

1. Natural language (derived-term system) ‏ Characteristics are: Improves recall because it provides more access points but reduces precision Redundancy is greater Uses more current terms Tends to be favored by subject-specialists or the end-users May also be called indexing by extraction (or extractive indexing method).

2. Controlled vocabulary (assigned-term system) ‏ Functions: To control synonyms by choosing one form as the standard term To make distinctions among homographs To bring or link together terms that are closely related Establishes the size of scope of a term Usually records hierarchical and affinitive/associative relations Controls variant spellings

Syndetic devices used by a controlled vocabulary: USE and UF (use for) for synonyms BT (broader term), NT (narrower term) and RT (related term) for differing levels of specificity and certain near synonyms and antonyms

Advantages of Controlled Vocabulary Language Increases the probability that both indexer and searcher will express a particular concept in the same way. Increases the probability that the same term will be used by different indexers or by the same indexer at different times. Helps searchers to focus their thoughts when they approach the information system without a full and precise realization of what information they need.

Disadvantages of Controlled Vocabulary Language : Incompatibility of different indexing languages. High input cost. The possibility of inadequate vocabulary.

Authority List / Subject Authority List a related group of words or phrase adopted by a particular group of people. Examples: Library of Congress Subject Headings Sears List of Subject Headings Dewey Decimal Classification Types of Controlled Vocabulary

Thesaurus Latin word means ‘treasure’, & is used to control indexing vocabulary It is a set of terms structured using a small set of semantic relationships between the term/ concepts. Poly-hierachical Examples: The Art & Architecture Thesaurus* ERIC (Education Resouces Information Center) Thesaurus*

Similarities between Authority Lists and Thesauri Both attempts to provide subject access to information resources by providing terminology that can be consistent rather than uncontrolled and unpredictable. Both choose preferred terms and make references from non-used terms. Both provide hierarchies so that terms are presented in relation to their broader, narrower, and related terms.

Difference between Authority Lists and Thesauri Thesauri are made up of single terms and bound terms representing single concepts. Subject heading lists have phrases and other pre-coordinated terms in addition to single terms. Thesauri are more strictly hierarchical. Thesauri are narrow in scope. Thesauri are more likely multilingual.

Relationships of Terms INTELLIGENCE BT: Ability NT: Comprehension RT: Talent Aptitude Broader term (BT) reference shows hierarchical relationship upward in the classification tree. Narrower term (NT) reference is similar to the broader term reference, except it goes down in the classification tree. Related term (RT) reference refers to a descriptor that can be used in addition to the basic term but is not in a hierarchical relationship.

Use for (UF) reference deals primarily with synonymous or variant forms of the preferred descriptor. It is also used to lead the indexer to more general terms. TREES UF Pecan trees PROMOTION POLICIES UF Automatic promotion

Use reference refers to a preferred descriptor from a non-usable term. Examples: Pecan trees USE TREES Oak trees USE TREES

Scope Note (SN) is used to give the users about the descriptor’s usage restrictions or to clarify ambiguity. Example: CULTURAL BACKGROUND SN: The total social heritage and experience of an individual or group including institutions, folkways, literature, mores, and communal experience.

Construction of a Thesaurus 1. Identify the subject field. 2. Identify the nature of literature to be indexed. 3. Identify the users. 4. Identify the file structure. Will this be a pre- coordinate or post-coordinate system? 5. Consult published indexes, glossaries, dictionaries, and other tools in the subject areas for the raw vocabulary. 6. Cluster the terms. 7. Establish term relationships.