INDEXING LANGUAGES AND SYSTEMS

INDEXING SYSTEMS FORMS OF INDEXES may be divided into two based on the COORDINATION of terms: Pre and Post coordinate indexing systems.

Coordination = building or assembling of index terms A: PRE-CORDINATE INDEXING SYSTEM: Designates the index term from an already authoritative source at the indexing stage.

Role of Pre-Coordinate Indexing: Combine terms in such a way that the resulting index headings will be as helpful as possible to persons searching for useful documentary units.

Criteria of Pre-Coordinate Indexing Eliminability: Predictability: Collocation: Clarity: Succinctness 1

Approaches to Combination of Terms • exact match syntax using boolean operators (AND, OR, NOT) to create combinations on the basis of boolean logic • best match syntax using terms with weights (indicating importance) to rank documents according to predicted relevance to a query, based on relationships between query terms and index terms generated from documentary units or their records 2

B: POST CORDINATE INDEXING SYSTEM • Terms are combined at the time of search, after indexing (if any!) has taken place and after the indexing system has been put into place

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INDEXING LANGUAGES What is an indexing language?

• vocabulary used to describe a specific concept in an index • Terms that may be used as access points in an index • The retrieval language • The set of terms (vocabulary and the devices for handling the relationship between them in a system for providing index descriptions 4

Types of Indexing languages?

A: CONTROLLED INDEXING [ASSIGNED TERM SYSTEM] • Index terms or descriptors drawn from a set of standardized vocabulary of terms used to represent different concepts. • Both terms used to represent document & process of assigning documents are done by the indexer May either be alphabetical (thesaurus & subject headings) or classified (Ontologies & classification schemes) 5

Basis of Development Serves as a system for vocabulary control - choice of nuance form for words (nouns, verbs, adjectives, adverbs)

- choice of words to be used (synonyms & near synonyms, variant spelling, plural Vs singular, homographs, etc.)

Promote consistent representation of subject matter thereby collocating related materials Promote comprehensive searches (Source – Lancaster, F.W. Vocabulary control for information retrieval)

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General Principals for Creating Controlled Vocabularies It should be based on literary warrant Must provide for direct entry of concepts under the term that names it It must be sufficiently pre-coordinated It should promote consistency Show relationships between the concepts

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Principals for Applying Terms from Controlled Vocabularies  Specific entry As available in the controlled vocabulary  Number of terms assigned Based on whether conceptual was done on summarization level of in-depth analysis  Concept not in the controlled vocabulary Provide provisional general concept

Terms for names Use of name authority files for proper names 8

Advantages of Controlled Vocabularies: (1)They standardize vocabulary Example: (excerpt from MeSH) "Decubitus Ulcer" INSTEAD OF "Bedsore", "Pressure Ulcer", or "Pressure Sore“ (2) They define topics or subjects to reduce ambiguity. Example (excerpt from MeSH) Child age 6-12 years Child, Preschool age 2-5 years 9

Advantages of Controlled Vocabularies cont.

(3) They standardize phrasing: Controlled vocabularies may use multiword descriptors: "Pancreatitis" "Pancreatitis, Acute Necrotizing" "Pancreatitis, Alcoholic“ (4) They pre-coordinate (combine) topics: "Housing for the Eldery" "Lung Transplantation" "Injections, Spinal" 10

Advantages of Controlled Vocabularies cont.

(5) Provide additional access points Through cross references

(6) Allow for identification of the most central or important concepts in a text (7) Allow for stability (8) Provide defined specificity & exhaustivity (9) Enhances precision e.g.

“Turkey” = Country:

“Turkey” = Bird:

(10)Enhances recall e.g.

Author 1: Dog: Author 2: Chien: Author 3: Canine Indexer: Dogs

(11) Promotes consistency 11

Advantages of Controlled Vocabularies cont.

(12) Shows relationships between the various concepts [syndetic structure] Hierarchical Relationships 1.Broader Terms 2.Narrower Terms.

See Related Cross References Links to related terms which may be of interest. blood glucose see related hyperglycemia hypoglycemia

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Advantages of Controlled Vocabularies cont.

See Cross References 1.Provide help finding the correct term from commonly used synonyms . (a) Instructional Technology see Educational Technology 2.Provide links from unused narrower terms to a broader terms. (b) Apples see Fruit 13

Disadvantages of Controlled Vocabulary  Limited variability  Require Indexer expertise and subject knowledge  Lacks exhaustivity & Specificity  Prone to errors – misconstrued conceptual analysis  High input cost  Incompatability causes barrier to exchange of data  Difficult to update etc., 14

B: NATURAL INDEXING [DERIVED TERM SYSTEM]

Uses the natural language of the document to derive the index terms.

Often associated with computer aided indexing Qualities of a Good Natural Language System • The quality of the complete index heading • The adequacy of the access provided to the terms and its collocation with related entries 15

Advantages of Natural-language Systems

Advantages of Natural-language Systems • Unlimited specificity and exhaustively.

• Creation of browsable displayed indexes.

• Cheaper and faster in creation of indexes • Allows for unlimited term combination thus enhancing specificity • Responsive to changes • Easy for computerization Dis-Advantages of Natural-language Systems • Uncontrolled thus infinitely variable i.e. lack precision • May increase recall to the point of unusability Places a greater burden on the user • Decreases precision – more false drops C: FREE TEXT INDEXING • A flexible, case by case (ad hoc) indexing.

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