Facet analysis is a fascinating way of dividing concepts presented in a subject or information domain into consistent sections.
For example, the subject of 'historic buildings' contain facets
PURPOSE (house, church, school),
STYLE (Gothic, classical, Arts and Crafts),
CONSTRUCTION (stone, brick, timber),
AGE (Victorian, Mediaeval)
This style of analysis finds use in the construction of classifications and thesauri, the design of interfaces, the construction of complex search logics, and more.