canons of Classification

Canons of Classification

Notes S.R. Ranganathan's Canons of Classification across the three planes of work, expanding on the specific rules and examples that guide library classification design.

1. Canons for the Idea Plane (Detailed)

The Idea Plane involves the core intellectual work of defining subjects, choosing characteristics for division, and arranging concepts. Ranganathan provided five key sets of canons for this plane:

A. Canons of Characteristics

These canons dictate how a group of entities should be divided into smaller groups (facets) using specific attributes (characteristics).

  • Canon of Differentiation: The chosen characteristic must divide a group into at least two distinct sub-groups. Example: You cannot divide bicycles by "number of wheels" (all have two), but you can differentiate them by "kind of rider" (gents, ladies, children).
  • Canon of Ascertainability: The characteristic must be verifiable and certain. Example: You cannot classify living people by their "previous birth" or "date of death" (which is uncertain), but you can by ascertainable facts like nationality or gender.
  • Canon of Permanence: The characteristic should be stable and not subject to frequent change. Example: Chameleons cannot be grouped by color since it changes; clothing color is also a poor characteristic for grouping people.
  • Canon of Relevance: The division must be relevant to the purpose of the classification. Example: A class of language learners should not be divided by body weight, as it has no relevance to their learning ability.

B. Canons for Succession of Characteristics

When multiple characteristics are applied to narrow down a subject, the sequence of their application is crucial.

  • Canon of Concomitance: Two different characteristics applied consecutively should not produce the exact same sub-classes. Example: Dividing people by "below 20 years old" and then by "born after 2006" produces the same group.
  • Canon of Relevant Succession: The sequence of characteristics must be highly relevant to the users' needs. Example: In Literature, applying characteristics as Language → Form → Author → Work serves language scholars best, while Form → Language → Author → Work serves scholars studying a specific genre (like poetry) across all languages.
  • Canon of Consistent Succession: Once an order of characteristics is chosen, it must be followed consistently unless the fundamental purpose of the classification changes.

C. Canons for Arrays

An array is a sequence of coordinate classes (entities of equal rank, like the continents of the Earth or the children of one parent).

  • Canon of Exhaustiveness: An array must include all eligible members. Example: Dividing mankind's skin color only into "White, Black, and Brown" is not exhaustive because it leaves out other variations.
  • Canon of Exclusiveness: An entity should belong to one, and only one, class within an array to prevent cross-classification. Example: A dog should be classified either under "mammals" or "pets," but not both within the same array.
  • Canon of Helpful Sequence: Entities should be arranged in a logical, predictable, and helpful order (e.g., chronological, alphabetical, or evolutionary).
  • Canon of Consistent Sequence: If the same set of entities appears in different main classes, their arrangement should remain identical everywhere. Example: The terms "male, female, child" should appear in the same order whether in Psychology, Education, or Law.

2. Canons for the Verbal Plane (Detailed)

The Verbal Plane handles the terminology and language used in the classification schedules. The goal is to eliminate ambiguity, homonyms, and synonyms.

  • Canon of Context: Terms should be written and read in the context of their broader upper class to ensure brevity. Example: Under the main heading "Salts," the sub-headings should just be "Single," "Double," and "Complex," rather than repeating "Single Salts," "Double Salts," etc.
  • Canon of Enumeration: When the scope of a subject is debatable (e.g., is "Dynamics" part of Physics or Mathematics?), the classification scheme should clearly define its boundaries by explicitly listing (enumerating) its subdivisions.
  • Canon of Currency: Terminology must not be frozen; it must reflect current, accepted usage among subject specialists. Example: Updating "Library Science" to "Library and Information Science."
  • Canon of Reticence: Terms used should be neutral, non-judgmental, and objective. Example: A classification system should never use subjective terms like "minor authors" or derogatory terms like "humbugs" for certain fields of study.

3. Canons for the Notational Plane (Detailed)

The Notational Plane is the "executive" plane that provides symbols (numbers/letters) to represent the concepts finalized in the Idea and Verbal planes.

  • Canon of Relativity and Uniformity: The length of a class number (the number of digits) should indicate the breadth (extension) and depth (intension) of the subject. As a subject becomes more specific, the class number should grow longer (e.g., 02 for Library Science, 025 for Library Operations, 025.3 for Bibliographic Control).
  • Canon of Hierarchy: Implied within relativity, this canon demands that every single characteristic used to divide a universe of entities must be represented by a specific digit in the final notation, faithfully mirroring the deepening hierarchy of the subject.