6. Why and When to use a Particular Structure

6.1 Advantages and Disadvantages of Particular Structures (Appendix B.2)

Lists:

• Simple to implement, use, and maintain
• Provide little or no guidance for the user

Synonym Rings:

• Are constructed manually and are not used in indexing
• Can be useful in retrieval as they allow synonyms and near-synonyms to be treated equally in searching.

Taxonomies

• Good information about hierarchical relationships among terms
• Useful for both indexers and searchers who need to discover the most appropriate, specific terms for their purposes
• There is no entry vocabulary, (i.e. USE/USED FOR terms)
• Taxonomies do not indicate other types of relationships among terms

Thesauri

• Good information about hierarchical relationships among terms
• Good information about relationships among terms
• Entry vocabulary to help users locate the correct terms
• Thesauri are useful for both indexers and searchers who need to discover the most appropriate, specific terms for their purposes
• Thesauri are time-consuming and labor intensive to develop and maintain

6.2 Typical applications of Lists, Synonym Rings, Taxonomies, and Thesauri (Appendix B.3)

Lists

Lists are frequently used to display small sets of terms that are to be used for quite narrowly defined purposes such as a web pull-down list or list of menu choices.

Synonym Rings

Synonym rings are frequently used behind-the-scenes to enhance retrieval, especially in an environment in which the indexing uses an uncontrolled vocabulary and/or there is no indexing as when searching full text.

Taxonomies

Taxonomies are often created and used in indexing applications and for web navigation. Because of their (usually simple) hierarchical structure) they are effective at leading users to the most specific terms available in a particular domain.

Thesauri

Thesauri are the most typical form of controlled vocabulary developed for use in indexing and searching applications because they provide the richest structure and cross-reference environment. Thesauri can be narrow in scope and cover a limited domain or they can be broad in scope and widely applicable to many different types of content.

6.3 Properties of Lists, Synonym rings, Taxonomies, and Thesauri (Appendix B.1)

Table 3: Controlled vocabulary properties

| 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