faceted classification

Faceted classification assigns multiple independent attributes (facets) to each item rather than placing it in a single hierarchical category. Each facet represents a different dimension of the item — subject, format, audience, date, geographic scope — and users can combine facets to narrow their search.

The approach was developed by Ranganathan in the 1930s as the Colon Classification, motivated by the observation that rigid hierarchies cannot accommodate the cross-cutting nature of real knowledge [@ranganathan_ProlegomenaLibraryClassification_1967]. A book about the economic history of Indian agriculture belongs simultaneously to economics, history, agriculture, and India — forcing it into one category loses the others.

Faceted classification is widely used in e-commerce (filter by price, brand, color, size) and increasingly in knowledge management, where tags and metadata fields serve as informal facets [@spiteri_SimplifiedModelFacetAnalysis_1998].