According to the Canon of Relativity and Uniformity, the length of a class number indicates:

The Correct answer is the breadth and depth of a subject.

Key Points

• Ranganathan’s Canons of Notation provide guidelines for designing a qualitative and effective notational system in library classification. These include:

Canon of Homonym and Synonym:

• Each class number should denote a unique subject, and each subject should have a unique class number.
• However, this is idealistic, and in practice, many subjects share the same class number.
• For example, in DDC, 610 always refers to medical science, while languages like Bengali share the same number 491.44.

Canon of Relativity and Uniformity:

• The class number's length reflects the subject's breadth (extension) and depth (intension).
• However, in practical use, some classifications may stop expanding the class number to maintain simplicity, e.g., the National Library of Medicine Classification.

Canon of Hierarchy:

• Class numbers should faithfully represent the hierarchy of subjects.
• However, many systems, like the DDC, may limit the depth of hierarchy for simplicity.

Canon of Mixed Notation:

• Mixed notation, involving multiple types of digits, is necessary for effective classification.
• Pure notations are too limited for the growing complexity of knowledge.
• For instance, the Library of Congress Classification combines alphabets and numerals, while the UDC mixes numerals and symbols.

Canon of Faceted Notation:

• Notation should clearly show the different facets of a subject.
• For example, in UDC and DDC, the hierarchical structure is represented through notation, but in Ranganathan’s system, it is more transparent.

Canon of Co-extensiveness:

• Each aspect of a subject should be represented by a separate digit.
• However, many systems fail to represent every characteristic in the class number, leading to homonymous class numbers.