Faceted classification

Faceted classification describes each item along several independent dimensions — facets — instead of placing it in one position of a single hierarchy. The idea goes back to S. R. Ranganathan's Colon Classification in the 1930s; on the web it became familiar as the filters of online shops.

How it works

Each facet is a small Taxonomy or list of values. A maintenance procedure might be classified as:

Facet	Value
Product	Pump series P200
Component	Seal assembly
Task	Replace
Audience	Service technician
Lifecycle phase	Maintenance

Users combine facets to narrow down results, in any order — which fits different Mental models at the same time.

Why it suits technical documentation

Product variants multiply quickly. A single tree ("Product > Variant > Chapter") duplicates structure for every variant; facets describe the variant once, as Metadata. Standards such as iiRDS define facets like product variant, component, lifecycle phase and information type for exactly this reason.

Design notes

• Keep facets orthogonal: one facet shouldn't encode another
• Use a Controlled vocabulary for every facet's values
• Show only facets that matter for the current result set, as part of Navigation systems