Species of Library Classification

The Species of Library Classification refer to different categories or types of classification schemes, primarily distinguished by their structure and methodology for listing subjects and constructing class numbers. Classification schemes are organized based on their scope, structure (ranging from fully enumerative to freely faceted), methodology, and other characteristics.

The sources identify the following species of classification schemes based on their structure and methodology:

Structural Categories (Evolutionary Species)

Classification schemes are generally categorized based on how rigidly or flexibly they enumerate subjects and provide for combining concepts (synthesis):

1. Enumerative Classification

The literal meaning of "Enumeration" is to list or count.

• Definition and Methodology: An enumerative classification scheme is one where all the possible classes are enumerated (listed) according to certain characteristics. It employs a top-down approach, producing a series of subordinate classes where both simple and complex subjects are listed. The basic tenet is that all possible subjects and topics are listed along with a predefined class number, so the classifier does not have to create any class number.
• Structure: It consists essentially of a single schedule enumerating all subjects—of the past, the present, and the anticipatable future. There are no separate supplementary schedules of common isolates to construct a number.
• Examples: The Library of Congress Classification (LC) is cited as a good example and prototype of this species. LC consists of a long schedule (11,300 pages in 45 volumes) with no provision for synthesis of numbers. Another example is Rider's International Classification (RIC).
• Limitations: It is difficult to accommodate new subjects, often requiring frequent revisions. Such schemes are considered classifications of the past and struggle to meet the challenges posed by the complexity of the growing universe of knowledge.

2. Almost-Enumerative Classification

• Definition and Methodology: This scheme consists of a large schedule enumerating most subjects, but also includes a few schedules of common isolates. While the majority of documents receive ready-made class numbers, a preliminary synthesis is possible with the help of supplementary schedules.
• Examples: Subject Classification (SC) by J.D. Brown, which appended a Categorical Table (listing forms and divisions used with any class), providing limited notational synthesis. The Dewey Decimal Classification (DDC), although devised as an enumerative scheme, has absorbed the structure and methodology of faceted classification in subsequent revisions by expanding its subsidiary tables and 'divide like' devices. DDC is considered an "almost-enumerative classification".

3. Almost-Faceted Classification

• Definition and Methodology: Lying between almost-enumerative and fully faceted classifications, this species has a long schedule of basic, compound, and complex subjects (of the past, present, and future), along with schedules of common isolates and special isolates. Indicator digits or connecting symbols are used to attach the isolates.
• Examples: Universal Decimal Classification (UDC) and the first edition of Bibliographic Classification (BC 1). Most numbers are still readymade, but many more can be synthesized using auxiliary tables.

4. Fully Faceted Classification (Analytico-Synthetic Classification)

This approach is on the extreme opposite side of the enumerative scale.

• Definition and Methodology: Instead of listing all classes, it lists the various facets of every subject or main class and provides a set of rules (grammar) for constructing class numbers through facet analysis. Faceted classification schemes consist only of schedules of basic classes, special isolates, and common isolates. No compound or complex subjects are enumerated readymade.
• Analytico-Synthetic Nature: Subjects are divided into constituent elements (analysis), and notations for each element are combined according to prescribed rules to prepare the final class number (synthesis). Since the work involves analysis and synthesis, it is also called Analytico-Synthetic Classification.
• Advantages: This species is better equipped to meet the challenges of the growing universe of knowledge. Its resilience is virtually infinite, and the resulting class numbers are co-extensive, brief, and elegant.
• Fundamental Categories: The core idea is that any component of a subject can fit into the Five Fundamental Categories (PMEST): Personality, Matter, Energy, Space, and Time.

The two types of fully faceted classification are:

• Rigidly-Faceted Classification: The first stage in the development of faceted schemes, where the facets and their citation order are fixed and predetermined (e.g., a fixed facet formula for each basic class). The first three editions of Colon Classification (CC) (1931, 1939, 1950) are considered rigidly-faceted.
• Freely Faceted Classification: The last stage in evolution, based on postulates and principles, where no rigid, predetermined facet formula exists for compound subjects. Each subject determines its own facet formula, which is "open". Examples include Colon Classification (CC) Edition 4 onwards (1952-1960) and Bibliographic Classification Edition 2 (BC-2).

Other Types of Classification Schemes (Based on Scope/Use)

Classification schemes can also be categorized based on their coverage or application:

• Universal Schemes: Schemes that are globally accepted, multilingual, and multidisciplinary in nature, covering all subject areas. Examples include UDC, DDC, and LC.
• National Schemes: Schemes designed specifically for a country, often possessing a geographic bias and usually lacking multilingual capability as a primary concern. Examples include Nederland’s Basisclassificatie (BC) and Sveriges Allmäma Biblioteks for ending (SAB).
• Subject Specific Schemes: Schemes usually created for special collections or indexing/abstracting services in a specific scientific discipline. They provide a structure and terminology much closer to the discipline and can be more up-to-date than universal schemes. Examples include the National Library of Medicine (NLM) classification.
• Homegrown Systems and Local Adaptations: Systems developed locally for specific library needs.